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</pre><pre class="rust"><code><span class="kw">use</span> <span class="ident">std::collections</span>::{<span class="ident">BTreeMap</span>, <span class="ident">HashMap</span>, <span class="ident">HashSet</span>};

<span class="kw">use</span> <span class="ident">anyhow::Result</span>;
<span class="kw">use</span> <span class="ident">lyon_geom::math::F64Point</span>;
<span class="kw">use</span> <span class="ident">lyon_geom</span>::{<span class="ident">CubicBezierSegment</span>, <span class="ident">QuadraticBezierSegment</span>};

<span class="kw">use</span> <span class="ident">geom</span>::{<span class="ident">Angle</span>, <span class="ident">Distance</span>, <span class="ident">PolyLine</span>, <span class="ident">Pt2D</span>};

<span class="kw">use</span> <span class="kw">crate</span>::{<span class="ident">Intersection</span>, <span class="ident">Lane</span>, <span class="ident">LaneID</span>, <span class="ident">LaneType</span>, <span class="ident">Map</span>, <span class="ident">RoadID</span>, <span class="ident">Turn</span>, <span class="ident">TurnID</span>, <span class="ident">TurnType</span>};

<span class="doccomment">/// Generate all driving and walking turns at an intersection, accounting for OSM turn restrictions.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">make_all_turns</span>(<span class="ident">map</span>: <span class="kw-2">&amp;</span><span class="ident">Map</span>, <span class="ident">i</span>: <span class="kw-2">&amp;</span><span class="ident">Intersection</span>) -&gt; <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Turn</span><span class="op">&gt;</span> {
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">raw_turns</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Turn</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">Vec::new</span>();
    <span class="ident">raw_turns</span>.<span class="ident">extend</span>(<span class="ident">make_vehicle_turns</span>(<span class="ident">i</span>, <span class="ident">map</span>));
    <span class="ident">raw_turns</span>.<span class="ident">extend</span>(<span class="ident"><span class="kw">crate</span>::make::walking_turns::filter_turns</span>(
        <span class="ident"><span class="kw">crate</span>::make::walking_turns::make_walking_turns</span>(<span class="ident">map</span>, <span class="ident">i</span>),
        <span class="ident">map</span>,
        <span class="ident">i</span>,
    ));
    <span class="kw">let</span> <span class="ident">unique_turns</span> <span class="op">=</span> <span class="ident">ensure_unique</span>(<span class="ident">raw_turns</span>);
    <span class="comment">// Never allow turns that go against road-level turn restrictions; that upstream OSM data is</span>
    <span class="comment">// usually not extremely broken.</span>
    <span class="kw">let</span> <span class="ident">all_turns</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Turn</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">unique_turns</span>
        .<span class="ident">into_iter</span>()
        .<span class="ident">filter</span>(<span class="op">|</span><span class="ident">t</span><span class="op">|</span> <span class="ident">t</span>.<span class="ident">permitted_by_road</span>(<span class="ident">i</span>, <span class="ident">map</span>))
        .<span class="ident">collect</span>();

    <span class="comment">// Try to use turn lane tags...</span>
    <span class="kw">let</span> <span class="ident">filtered_turns</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Turn</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">all_turns</span>
        .<span class="ident">clone</span>()
        .<span class="ident">into_iter</span>()
        .<span class="ident">filter</span>(<span class="op">|</span><span class="ident">t</span><span class="op">|</span> <span class="ident">t</span>.<span class="ident">permitted_by_lane</span>(<span class="ident">map</span>))
        .<span class="ident">collect</span>();
    <span class="comment">// And remove merging left or right turns. If we wanted to remove the &quot;lane-changing at</span>
    <span class="comment">// intersections&quot; behavior, we could do this for TurnType::Straight too.</span>
    <span class="kw">let</span> <span class="ident">filtered_turns</span> <span class="op">=</span> <span class="ident">remove_merging_turns</span>(<span class="ident">map</span>, <span class="ident">filtered_turns</span>, <span class="ident">TurnType::Right</span>);
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">filtered_turns</span> <span class="op">=</span> <span class="ident">remove_merging_turns</span>(<span class="ident">map</span>, <span class="ident">filtered_turns</span>, <span class="ident">TurnType::Left</span>);
    <span class="kw">if</span> <span class="ident">i</span>.<span class="ident">merged</span> {
        <span class="ident">filtered_turns</span>.<span class="ident">retain</span>(<span class="op">|</span><span class="ident">turn</span><span class="op">|</span> {
            <span class="kw">if</span> <span class="ident">turn</span>.<span class="ident">turn_type</span> <span class="op">==</span> <span class="ident">TurnType::UTurn</span> {
                <span class="kw">let</span> <span class="ident">src_lane</span> <span class="op">=</span> <span class="ident">map</span>.<span class="ident">get_l</span>(<span class="ident">turn</span>.<span class="ident">id</span>.<span class="ident">src</span>);
                <span class="comment">// U-turns at divided highways are sometimes legal (and a common movement --</span>
                <span class="comment">// https://www.openstreetmap.org/way/361443212), so let OSM turn:lanes override.</span>
                <span class="kw">if</span> <span class="ident">src_lane</span>
                    .<span class="ident">get_lane_level_turn_restrictions</span>(<span class="ident">map</span>.<span class="ident">get_r</span>(<span class="ident">src_lane</span>.<span class="ident">id</span>.<span class="ident">road</span>), <span class="bool-val">false</span>)
                    .<span class="ident">map</span>(<span class="op">|</span><span class="ident">set</span><span class="op">|</span> <span class="op">!</span><span class="ident">set</span>.<span class="ident">contains</span>(<span class="kw-2">&amp;</span><span class="ident">TurnType::UTurn</span>))
                    .<span class="ident">unwrap_or</span>(<span class="bool-val">true</span>)
                {
                    <span class="macro">warn!</span>(<span class="string">&quot;Removing u-turn from merged intersection: {}&quot;</span>, <span class="ident">turn</span>.<span class="ident">id</span>);
                    <span class="bool-val">false</span>
                } <span class="kw">else</span> {
                    <span class="bool-val">true</span>
                }
            } <span class="kw">else</span> {
                <span class="bool-val">true</span>
            }
        });
    }

    <span class="comment">// But then see how all of that filtering affects lane connectivity.</span>
    <span class="kw">match</span> <span class="ident">verify_vehicle_connectivity</span>(<span class="kw-2">&amp;</span><span class="ident">filtered_turns</span>, <span class="ident">i</span>, <span class="ident">map</span>) {
        <span class="prelude-val">Ok</span>(()) =&gt; <span class="ident">filtered_turns</span>,
        <span class="prelude-val">Err</span>(<span class="ident">err</span>) =&gt; {
            <span class="macro">warn!</span>(<span class="string">&quot;Not filtering turns. {}&quot;</span>, <span class="ident">err</span>);
            <span class="ident">all_turns</span>
        }
    }
}

<span class="kw">fn</span> <span class="ident">ensure_unique</span>(<span class="ident">turns</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Turn</span><span class="op">&gt;</span>) -&gt; <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Turn</span><span class="op">&gt;</span> {
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">ids</span> <span class="op">=</span> <span class="ident">HashSet::new</span>();
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">keep</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Turn</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">Vec::new</span>();
    <span class="kw">for</span> <span class="ident">t</span> <span class="kw">in</span> <span class="ident">turns</span>.<span class="ident">into_iter</span>() {
        <span class="kw">if</span> <span class="ident">ids</span>.<span class="ident">contains</span>(<span class="kw-2">&amp;</span><span class="ident">t</span>.<span class="ident">id</span>) {
            <span class="comment">// TODO This was once an assertion, but disabled for</span>
            <span class="comment">// https://github.com/a-b-street/abstreet/issues/84. A crosswalk gets created twice</span>
            <span class="comment">// and deduplicated here. Not sure why it was double-created in the first place.</span>
            <span class="macro">warn!</span>(<span class="string">&quot;Duplicate turns {}!&quot;</span>, <span class="ident">t</span>.<span class="ident">id</span>);
        } <span class="kw">else</span> {
            <span class="ident">ids</span>.<span class="ident">insert</span>(<span class="ident">t</span>.<span class="ident">id</span>);
            <span class="ident">keep</span>.<span class="ident">push</span>(<span class="ident">t</span>);
        }
    }
    <span class="ident">keep</span>
}

<span class="doccomment">/// Ideally, we want every incoming lane to lead to at least one lane of the same type, and every</span>
<span class="doccomment">/// outgoing lane to be reachable by at least one lane of the same type. But if it&#39;s a bus or bike</span>
<span class="doccomment">/// lane, settle for being connected to anything -- even just a driving lane. There&#39;s naturally</span>
<span class="doccomment">/// places where these dedicated lanes start and end.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Why is this definition strict for driving lanes connected to other driving lanes?  See</span>
<span class="doccomment">/// https://www.openstreetmap.org/node/491979474 for a motivating example. When a dedicated bike</span>
<span class="doccomment">/// path crosses a road with turn restrictions marked on a segment before the intersection, the</span>
<span class="doccomment">/// turn restrictions _probably_ indicate the vehicle movements allowed further on, and _don&#39;t_</span>
<span class="doccomment">/// describe the turns between the road and the trail.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">verify_vehicle_connectivity</span>(<span class="ident">turns</span>: <span class="kw-2">&amp;</span>[<span class="ident">Turn</span>], <span class="ident">i</span>: <span class="kw-2">&amp;</span><span class="ident">Intersection</span>, <span class="ident">map</span>: <span class="kw-2">&amp;</span><span class="ident">Map</span>) -&gt; <span class="prelude-ty">Result</span><span class="op">&lt;</span>()<span class="op">&gt;</span> {
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">incoming_missing</span>: <span class="ident">HashSet</span><span class="op">&lt;</span><span class="ident">LaneID</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">HashSet::new</span>();
    <span class="kw">for</span> <span class="ident">l</span> <span class="kw">in</span> <span class="kw-2">&amp;</span><span class="ident">i</span>.<span class="ident">incoming_lanes</span> {
        <span class="kw">if</span> <span class="ident">map</span>.<span class="ident">get_l</span>(<span class="kw-2">*</span><span class="ident">l</span>).<span class="ident">lane_type</span>.<span class="ident">is_for_moving_vehicles</span>() {
            <span class="ident">incoming_missing</span>.<span class="ident">insert</span>(<span class="kw-2">*</span><span class="ident">l</span>);
        }
    }
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">outgoing_missing</span>: <span class="ident">HashSet</span><span class="op">&lt;</span><span class="ident">LaneID</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">HashSet::new</span>();
    <span class="kw">for</span> <span class="ident">l</span> <span class="kw">in</span> <span class="kw-2">&amp;</span><span class="ident">i</span>.<span class="ident">outgoing_lanes</span> {
        <span class="kw">if</span> <span class="ident">map</span>.<span class="ident">get_l</span>(<span class="kw-2">*</span><span class="ident">l</span>).<span class="ident">lane_type</span>.<span class="ident">is_for_moving_vehicles</span>() {
            <span class="ident">outgoing_missing</span>.<span class="ident">insert</span>(<span class="kw-2">*</span><span class="ident">l</span>);
        }
    }

    <span class="kw">for</span> <span class="ident">turn</span> <span class="kw">in</span> <span class="ident">turns</span> {
        <span class="kw">let</span> <span class="ident">src_lt</span> <span class="op">=</span> <span class="ident">map</span>.<span class="ident">get_l</span>(<span class="ident">turn</span>.<span class="ident">id</span>.<span class="ident">src</span>).<span class="ident">lane_type</span>;
        <span class="kw">let</span> <span class="ident">dst_lt</span> <span class="op">=</span> <span class="ident">map</span>.<span class="ident">get_l</span>(<span class="ident">turn</span>.<span class="ident">id</span>.<span class="ident">dst</span>).<span class="ident">lane_type</span>;

        <span class="kw">if</span> <span class="ident">src_lt</span> <span class="op">==</span> <span class="ident">dst_lt</span> {
            <span class="ident">incoming_missing</span>.<span class="ident">remove</span>(<span class="kw-2">&amp;</span><span class="ident">turn</span>.<span class="ident">id</span>.<span class="ident">src</span>);
            <span class="ident">outgoing_missing</span>.<span class="ident">remove</span>(<span class="kw-2">&amp;</span><span class="ident">turn</span>.<span class="ident">id</span>.<span class="ident">dst</span>);
        }

        <span class="kw">if</span> <span class="ident">src_lt</span> <span class="op">==</span> <span class="ident">LaneType::Biking</span> <span class="op">|</span><span class="op">|</span> <span class="ident">src_lt</span> <span class="op">==</span> <span class="ident">LaneType::Bus</span> {
            <span class="ident">incoming_missing</span>.<span class="ident">remove</span>(<span class="kw-2">&amp;</span><span class="ident">turn</span>.<span class="ident">id</span>.<span class="ident">src</span>);
        }
        <span class="kw">if</span> <span class="ident">dst_lt</span> <span class="op">==</span> <span class="ident">LaneType::Biking</span> <span class="op">|</span><span class="op">|</span> <span class="ident">dst_lt</span> <span class="op">==</span> <span class="ident">LaneType::Bus</span> {
            <span class="ident">outgoing_missing</span>.<span class="ident">remove</span>(<span class="kw-2">&amp;</span><span class="ident">turn</span>.<span class="ident">id</span>.<span class="ident">dst</span>);
        }
    }

    <span class="kw">if</span> <span class="op">!</span><span class="ident">incoming_missing</span>.<span class="ident">is_empty</span>() <span class="op">|</span><span class="op">|</span> <span class="op">!</span><span class="ident">outgoing_missing</span>.<span class="ident">is_empty</span>() {
        <span class="macro">bail!</span>(
            <span class="string">&quot;Turns for {} orphan some lanes. Incoming: {:?}, outgoing: {:?}&quot;</span>,
            <span class="ident">i</span>.<span class="ident">id</span>,
            <span class="ident">incoming_missing</span>,
            <span class="ident">outgoing_missing</span>
        );
    }
    <span class="prelude-val">Ok</span>(())
}

<span class="kw">fn</span> <span class="ident">make_vehicle_turns</span>(<span class="ident">i</span>: <span class="kw-2">&amp;</span><span class="ident">Intersection</span>, <span class="ident">map</span>: <span class="kw-2">&amp;</span><span class="ident">Map</span>) -&gt; <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Turn</span><span class="op">&gt;</span> {
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">turns</span> <span class="op">=</span> <span class="ident">Vec::new</span>();

    <span class="kw">let</span> <span class="ident">expected_turn_types</span> <span class="op">=</span> <span class="ident">expected_turn_types_for_four_way</span>(<span class="ident">i</span>, <span class="ident">map</span>);

    <span class="comment">// Just generate every possible combination of turns between incoming and outgoing lanes.</span>
    <span class="kw">let</span> <span class="ident">is_deadend</span> <span class="op">=</span> <span class="ident">i</span>.<span class="ident">roads</span>.<span class="ident">len</span>() <span class="op">==</span> <span class="number">1</span>;
    <span class="kw">for</span> <span class="ident">src</span> <span class="kw">in</span> <span class="kw-2">&amp;</span><span class="ident">i</span>.<span class="ident">incoming_lanes</span> {
        <span class="kw">let</span> <span class="ident">src</span> <span class="op">=</span> <span class="ident">map</span>.<span class="ident">get_l</span>(<span class="kw-2">*</span><span class="ident">src</span>);
        <span class="kw">if</span> <span class="op">!</span><span class="ident">src</span>.<span class="ident">lane_type</span>.<span class="ident">is_for_moving_vehicles</span>() {
            <span class="kw">continue</span>;
        }
        <span class="kw">for</span> <span class="ident">dst</span> <span class="kw">in</span> <span class="kw-2">&amp;</span><span class="ident">i</span>.<span class="ident">outgoing_lanes</span> {
            <span class="kw">let</span> <span class="ident">dst</span> <span class="op">=</span> <span class="ident">map</span>.<span class="ident">get_l</span>(<span class="kw-2">*</span><span class="ident">dst</span>);
            <span class="kw">if</span> <span class="op">!</span><span class="ident">dst</span>.<span class="ident">lane_type</span>.<span class="ident">is_for_moving_vehicles</span>() {
                <span class="kw">continue</span>;
            }
            <span class="comment">// Only allow U-turns at deadends</span>
            <span class="kw">if</span> <span class="ident">src</span>.<span class="ident">id</span>.<span class="ident">road</span> <span class="op">==</span> <span class="ident">dst</span>.<span class="ident">id</span>.<span class="ident">road</span> <span class="op">&amp;&amp;</span> <span class="op">!</span><span class="ident">is_deadend</span> {
                <span class="kw">continue</span>;
            }
            <span class="comment">// Can&#39;t go between light rail and normal roads</span>
            <span class="kw">if</span> <span class="ident">src</span>.<span class="ident">is_light_rail</span>() <span class="op">!</span><span class="op">=</span> <span class="ident">dst</span>.<span class="ident">is_light_rail</span>() {
                <span class="kw">continue</span>;
            }
            <span class="kw">if</span> <span class="ident">src</span>.<span class="ident">last_pt</span>() <span class="op">==</span> <span class="ident">dst</span>.<span class="ident">first_pt</span>() {
                <span class="macro">warn!</span>(
                    <span class="string">&quot;No turn from {} to {}; the endpoints are the same&quot;</span>,
                    <span class="ident">src</span>.<span class="ident">id</span>, <span class="ident">dst</span>.<span class="ident">id</span>
                );
                <span class="kw">continue</span>;
            }

            <span class="kw">let</span> <span class="ident">from_angle</span> <span class="op">=</span> <span class="ident">src</span>.<span class="ident">last_line</span>().<span class="ident">angle</span>();
            <span class="kw">let</span> <span class="ident">to_angle</span> <span class="op">=</span> <span class="ident">dst</span>.<span class="ident">first_line</span>().<span class="ident">angle</span>();
            <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">turn_type</span> <span class="op">=</span> <span class="ident">turn_type_from_angles</span>(<span class="ident">from_angle</span>, <span class="ident">to_angle</span>);
            <span class="kw">if</span> <span class="ident">turn_type</span> <span class="op">==</span> <span class="ident">TurnType::UTurn</span> {
                <span class="comment">// Lots of false positives when classifying these just based on angles. So also</span>
                <span class="comment">// require the road names to match.</span>
                <span class="kw">if</span> <span class="ident">map</span>.<span class="ident">get_parent</span>(<span class="ident">src</span>.<span class="ident">id</span>).<span class="ident">get_name</span>(<span class="prelude-val">None</span>) <span class="op">!</span><span class="op">=</span> <span class="ident">map</span>.<span class="ident">get_parent</span>(<span class="ident">dst</span>.<span class="ident">id</span>).<span class="ident">get_name</span>(<span class="prelude-val">None</span>) {
                    <span class="comment">// Distinguish really sharp lefts/rights based on clockwiseness</span>
                    <span class="kw">if</span> <span class="ident">from_angle</span>.<span class="ident">simple_shortest_rotation_towards</span>(<span class="ident">to_angle</span>) <span class="op">&lt;</span> <span class="number">0.0</span> {
                        <span class="ident">turn_type</span> <span class="op">=</span> <span class="ident">TurnType::Right</span>;
                    } <span class="kw">else</span> {
                        <span class="ident">turn_type</span> <span class="op">=</span> <span class="ident">TurnType::Left</span>;
                    }
                }

                <span class="comment">// Some service roads wind up very short. Allowing u-turns there causes vehicles to</span>
                <span class="comment">// gridlock pretty much instantly, because they occupy two intersections during the</span>
                <span class="comment">// attempted movement.</span>
                <span class="kw">if</span> <span class="ident">is_deadend</span> <span class="op">&amp;&amp;</span> <span class="ident">src</span>.<span class="ident">length</span>() <span class="op">&lt;</span> <span class="ident">Distance::meters</span>(<span class="number">7.0</span>) {
                    <span class="macro">warn!</span>(<span class="string">&quot;Skipping U-turn at tiny deadend on {}&quot;</span>, <span class="ident">src</span>.<span class="ident">id</span>);
                    <span class="kw">continue</span>;
                }
            } <span class="kw">else</span> <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">expected_type</span>) <span class="op">=</span> <span class="ident">expected_turn_types</span>
                .<span class="ident">as_ref</span>()
                .<span class="ident">and_then</span>(<span class="op">|</span><span class="ident">e</span><span class="op">|</span> <span class="ident">e</span>.<span class="ident">get</span>(<span class="kw-2">&amp;</span>(<span class="ident">src</span>.<span class="ident">id</span>.<span class="ident">road</span>, <span class="ident">dst</span>.<span class="ident">id</span>.<span class="ident">road</span>)))
            {
                <span class="comment">// At some 4-way intersections, roads meet at strange angles, throwing off</span>
                <span class="comment">// turn_type_from_angles. Correct it based on relative ordering.</span>
                <span class="kw">if</span> <span class="ident">turn_type</span> <span class="op">!</span><span class="op">=</span> <span class="kw-2">*</span><span class="ident">expected_type</span> {
                    <span class="macro">warn!</span>(
                        <span class="string">&quot;Turn from {} to {} looks like {:?} by angle, but is {:?} by ordering&quot;</span>,
                        <span class="ident">src</span>.<span class="ident">id</span>.<span class="ident">road</span>, <span class="ident">dst</span>.<span class="ident">id</span>.<span class="ident">road</span>, <span class="ident">turn_type</span>, <span class="ident">expected_type</span>
                    );
                    <span class="ident">turn_type</span> <span class="op">=</span> <span class="kw-2">*</span><span class="ident">expected_type</span>;
                }
            }

            <span class="kw">let</span> <span class="ident">geom</span> <span class="op">=</span> <span class="ident">curvey_turn</span>(<span class="ident">src</span>, <span class="ident">dst</span>, <span class="ident">i</span>)
                .<span class="ident">unwrap_or_else</span>(<span class="op">|</span><span class="kw">_</span><span class="op">|</span> <span class="ident">PolyLine::must_new</span>(<span class="macro">vec!</span>[<span class="ident">src</span>.<span class="ident">last_pt</span>(), <span class="ident">dst</span>.<span class="ident">first_pt</span>()]));

            <span class="ident">turns</span>.<span class="ident">push</span>(<span class="ident">Turn</span> {
                <span class="ident">id</span>: <span class="ident">TurnID</span> {
                    <span class="ident">parent</span>: <span class="ident">i</span>.<span class="ident">id</span>,
                    <span class="ident">src</span>: <span class="ident">src</span>.<span class="ident">id</span>,
                    <span class="ident">dst</span>: <span class="ident">dst</span>.<span class="ident">id</span>,
                },
                <span class="ident">turn_type</span>,
                <span class="ident">geom</span>,
            });
        }
    }

    <span class="ident">turns</span>
}

<span class="kw">fn</span> <span class="ident">curvey_turn</span>(<span class="ident">src</span>: <span class="kw-2">&amp;</span><span class="ident">Lane</span>, <span class="ident">dst</span>: <span class="kw-2">&amp;</span><span class="ident">Lane</span>, <span class="ident">i</span>: <span class="kw-2">&amp;</span><span class="ident">Intersection</span>) -&gt; <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">PolyLine</span><span class="op">&gt;</span> {
    <span class="kw">fn</span> <span class="ident">to_pt</span>(<span class="ident">pt</span>: <span class="ident">Pt2D</span>) -&gt; <span class="ident">F64Point</span> {
        <span class="ident">lyon_geom::math::point</span>(<span class="ident">pt</span>.<span class="ident">x</span>(), <span class="ident">pt</span>.<span class="ident">y</span>())
    }

    <span class="kw">fn</span> <span class="ident">from_pt</span>(<span class="ident">pt</span>: <span class="ident">F64Point</span>) -&gt; <span class="ident">Pt2D</span> {
        <span class="ident">Pt2D::new</span>(<span class="ident">pt</span>.<span class="ident">x</span>, <span class="ident">pt</span>.<span class="ident">y</span>)
    }

    <span class="comment">// The control points are straight out/in from the source/destination lanes, so</span>
    <span class="comment">// that the car exits and enters at the same angle as the road.</span>
    <span class="kw">let</span> <span class="ident">src_line</span> <span class="op">=</span> <span class="ident">src</span>.<span class="ident">last_line</span>();
    <span class="kw">let</span> <span class="ident">dst_line</span> <span class="op">=</span> <span class="ident">dst</span>.<span class="ident">first_line</span>();

    <span class="kw">let</span> <span class="ident">src_pt</span> <span class="op">=</span> <span class="ident">src</span>.<span class="ident">last_pt</span>();
    <span class="kw">let</span> <span class="ident">dst_pt</span> <span class="op">=</span> <span class="ident">dst</span>.<span class="ident">first_pt</span>();

    <span class="kw">let</span> <span class="ident">src_angle</span> <span class="op">=</span> <span class="ident">src_line</span>.<span class="ident">angle</span>();
    <span class="kw">let</span> <span class="ident">dst_angle</span> <span class="op">=</span> <span class="ident">dst_line</span>.<span class="ident">angle</span>();

    <span class="kw">let</span> <span class="ident">intersection</span> <span class="op">=</span> <span class="ident">src_line</span>
        .<span class="ident">infinite</span>()
        .<span class="ident">intersection</span>(<span class="kw-2">&amp;</span><span class="ident">dst_line</span>.<span class="ident">infinite</span>())
        .<span class="ident">unwrap_or</span>(<span class="ident">src_pt</span>);

    <span class="kw">let</span> <span class="ident">curve</span> <span class="op">=</span>
        <span class="comment">// U-turns and straight turns</span>
        <span class="kw">if</span> <span class="ident">src_angle</span>.<span class="ident">approx_parallel</span>(<span class="ident">dst_angle</span>, <span class="number">5.0</span>)
        <span class="comment">// Zero length intersections (this results in PolyLine::new returning none)</span>
        <span class="op">|</span><span class="op">|</span> <span class="ident">src_pt</span>.<span class="ident">approx_eq</span>(<span class="ident">intersection</span>, <span class="ident">geom::EPSILON_DIST</span>)
        <span class="op">|</span><span class="op">|</span> <span class="ident">dst_pt</span>.<span class="ident">approx_eq</span>(<span class="ident">intersection</span>, <span class="ident">geom::EPSILON_DIST</span>)
        <span class="comment">// Weirdly shaped intersections where the lane lines intersect outside the intersection</span>
        <span class="op">|</span><span class="op">|</span> <span class="op">!</span><span class="ident">i</span>.<span class="ident">polygon</span>.<span class="ident">contains_pt</span>(<span class="ident">intersection</span>)
    {
        <span class="comment">// All get a curve scaled to the distance between the points</span>
        <span class="ident">CubicBezierSegment</span> {
            <span class="ident">from</span>: <span class="ident">to_pt</span>(<span class="ident">src_pt</span>),
            <span class="ident">ctrl1</span>: <span class="ident">to_pt</span>(<span class="ident">src_pt</span>.<span class="ident">project_away</span>(<span class="ident">src_pt</span>.<span class="ident">dist_to</span>(<span class="ident">dst_pt</span>) <span class="op">/</span> <span class="number">2.0</span>, <span class="ident">src_angle</span>)),
            <span class="ident">ctrl2</span>: <span class="ident">to_pt</span>(<span class="ident">dst_pt</span>.<span class="ident">project_away</span>(<span class="ident">src_pt</span>.<span class="ident">dist_to</span>(<span class="ident">dst_pt</span>) <span class="op">/</span> <span class="number">2.0</span>, <span class="ident">dst_angle</span>.<span class="ident">opposite</span>())),
            <span class="ident">to</span>: <span class="ident">to_pt</span>(<span class="ident">dst_pt</span>),
        }
    } <span class="kw">else</span> {
        <span class="comment">// Regular intersections get a quadratic bezier curve</span>
        <span class="ident">QuadraticBezierSegment</span> {
            <span class="ident">from</span>: <span class="ident">to_pt</span>(<span class="ident">src_pt</span>),
            <span class="ident">ctrl</span>: <span class="ident">to_pt</span>(<span class="ident">intersection</span>),
            <span class="ident">to</span>: <span class="ident">to_pt</span>(<span class="ident">dst_pt</span>),
        }.<span class="ident">to_cubic</span>()
    };

    <span class="kw">let</span> <span class="ident">pieces</span> <span class="op">=</span> <span class="number">5</span>;
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">curve</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Pt2D</span><span class="op">&gt;</span> <span class="op">=</span> (<span class="number">0</span>..<span class="op">=</span><span class="ident">pieces</span>)
        .<span class="ident">map</span>(<span class="op">|</span><span class="ident">i</span><span class="op">|</span> <span class="ident">from_pt</span>(<span class="ident">curve</span>.<span class="ident">sample</span>(<span class="number">1.0</span> <span class="op">/</span> <span class="ident">f64::from</span>(<span class="ident">pieces</span>) <span class="op">*</span> <span class="ident">f64::from</span>(<span class="ident">i</span>))))
        .<span class="ident">collect</span>();
    <span class="ident">curve</span>.<span class="ident">dedup</span>();
    <span class="ident">PolyLine::new</span>(<span class="ident">curve</span>)
}

<span class="kw">fn</span> <span class="ident">remove_merging_turns</span>(<span class="ident">map</span>: <span class="kw-2">&amp;</span><span class="ident">Map</span>, <span class="ident">input</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Turn</span><span class="op">&gt;</span>, <span class="ident">turn_type</span>: <span class="ident">TurnType</span>) -&gt; <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Turn</span><span class="op">&gt;</span> {
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">turns</span> <span class="op">=</span> <span class="ident">Vec::new</span>();

    <span class="comment">// Group turns of the specified type by (from, to) road</span>
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">pairs</span>: <span class="ident">BTreeMap</span><span class="op">&lt;</span>(<span class="ident">RoadID</span>, <span class="ident">RoadID</span>), <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Turn</span><span class="op">&gt;</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">BTreeMap::new</span>();
    <span class="kw">for</span> <span class="ident">t</span> <span class="kw">in</span> <span class="ident">input</span> {
        <span class="comment">// Only do this for driving lanes</span>
        <span class="kw">if</span> <span class="op">!</span><span class="ident">map</span>.<span class="ident">get_l</span>(<span class="ident">t</span>.<span class="ident">id</span>.<span class="ident">src</span>).<span class="ident">is_driving</span>() <span class="op">|</span><span class="op">|</span> <span class="op">!</span><span class="ident">map</span>.<span class="ident">get_l</span>(<span class="ident">t</span>.<span class="ident">id</span>.<span class="ident">dst</span>).<span class="ident">is_driving</span>() {
            <span class="ident">turns</span>.<span class="ident">push</span>(<span class="ident">t</span>);
            <span class="kw">continue</span>;
        }

        <span class="kw">if</span> <span class="ident">t</span>.<span class="ident">turn_type</span> <span class="op">==</span> <span class="ident">turn_type</span> {
            <span class="ident">pairs</span>
                .<span class="ident">entry</span>((<span class="ident">t</span>.<span class="ident">id</span>.<span class="ident">src</span>.<span class="ident">road</span>, <span class="ident">t</span>.<span class="ident">id</span>.<span class="ident">dst</span>.<span class="ident">road</span>))
                .<span class="ident">or_insert_with</span>(<span class="ident">Vec::new</span>)
                .<span class="ident">push</span>(<span class="ident">t</span>);
        } <span class="kw">else</span> {
            <span class="comment">// Other turn types always pass through</span>
            <span class="ident">turns</span>.<span class="ident">push</span>(<span class="ident">t</span>);
        }
    }

    <span class="kw">for</span> (<span class="kw">_</span>, <span class="ident">group</span>) <span class="kw">in</span> <span class="ident">pairs</span> {
        <span class="kw">if</span> <span class="ident">group</span>.<span class="ident">len</span>() <span class="op">==</span> <span class="number">1</span> {
            <span class="ident">turns</span>.<span class="ident">extend</span>(<span class="ident">group</span>);
            <span class="kw">continue</span>;
        }

        <span class="kw">let</span> <span class="ident">num_src_lanes</span> <span class="op">=</span> <span class="ident">group</span>.<span class="ident">iter</span>().<span class="ident">map</span>(<span class="op">|</span><span class="ident">t</span><span class="op">|</span> <span class="ident">t</span>.<span class="ident">id</span>.<span class="ident">src</span>).<span class="ident">collect</span>::<span class="op">&lt;</span><span class="ident">HashSet</span><span class="op">&lt;</span><span class="kw">_</span><span class="op">&gt;</span><span class="op">&gt;</span>().<span class="ident">len</span>();
        <span class="kw">let</span> <span class="ident">num_dst_lanes</span> <span class="op">=</span> <span class="ident">group</span>.<span class="ident">iter</span>().<span class="ident">map</span>(<span class="op">|</span><span class="ident">t</span><span class="op">|</span> <span class="ident">t</span>.<span class="ident">id</span>.<span class="ident">dst</span>).<span class="ident">collect</span>::<span class="op">&lt;</span><span class="ident">HashSet</span><span class="op">&lt;</span><span class="kw">_</span><span class="op">&gt;</span><span class="op">&gt;</span>().<span class="ident">len</span>();

        <span class="comment">// Allow all turns from one to many</span>
        <span class="kw">if</span> <span class="ident">num_src_lanes</span> <span class="op">==</span> <span class="number">1</span> {
            <span class="ident">turns</span>.<span class="ident">extend</span>(<span class="ident">group</span>);
            <span class="kw">continue</span>;
        }

        <span class="comment">// If the number of source and destination lanes is the same, match them up in order,</span>
        <span class="comment">// without any crossing.</span>
        <span class="kw">if</span> <span class="ident">num_src_lanes</span> <span class="op">==</span> <span class="ident">num_dst_lanes</span> {
            <span class="comment">// But we want to match things up -- leftmost turn lane leads to leftmost destination.</span>
            <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">src_lanes_in_order</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">LaneID</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">group</span>.<span class="ident">iter</span>().<span class="ident">map</span>(<span class="op">|</span><span class="ident">t</span><span class="op">|</span> <span class="ident">t</span>.<span class="ident">id</span>.<span class="ident">src</span>).<span class="ident">collect</span>();
            <span class="ident">src_lanes_in_order</span>.<span class="ident">sort_by_key</span>(<span class="op">|</span><span class="ident">l</span><span class="op">|</span> <span class="ident">map</span>.<span class="ident">get_parent</span>(<span class="kw-2">*</span><span class="ident">l</span>).<span class="ident">dir_and_offset</span>(<span class="kw-2">*</span><span class="ident">l</span>).<span class="number">1</span>);
            <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">dst_lanes_in_order</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">LaneID</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">group</span>.<span class="ident">iter</span>().<span class="ident">map</span>(<span class="op">|</span><span class="ident">t</span><span class="op">|</span> <span class="ident">t</span>.<span class="ident">id</span>.<span class="ident">dst</span>).<span class="ident">collect</span>();
            <span class="ident">dst_lanes_in_order</span>.<span class="ident">sort_by_key</span>(<span class="op">|</span><span class="ident">l</span><span class="op">|</span> <span class="ident">map</span>.<span class="ident">get_parent</span>(<span class="kw-2">*</span><span class="ident">l</span>).<span class="ident">dir_and_offset</span>(<span class="kw-2">*</span><span class="ident">l</span>).<span class="number">1</span>);

            <span class="kw">for</span> <span class="ident">t</span> <span class="kw">in</span> <span class="ident">group</span> {
                <span class="kw">let</span> <span class="ident">src_order</span> <span class="op">=</span> <span class="ident">src_lanes_in_order</span>
                    .<span class="ident">iter</span>()
                    .<span class="ident">position</span>(<span class="op">|</span><span class="ident">l</span><span class="op">|</span> <span class="ident">t</span>.<span class="ident">id</span>.<span class="ident">src</span> <span class="op">==</span> <span class="kw-2">*</span><span class="ident">l</span>)
                    .<span class="ident">unwrap</span>();
                <span class="kw">let</span> <span class="ident">dst_order</span> <span class="op">=</span> <span class="ident">dst_lanes_in_order</span>
                    .<span class="ident">iter</span>()
                    .<span class="ident">position</span>(<span class="op">|</span><span class="ident">l</span><span class="op">|</span> <span class="ident">t</span>.<span class="ident">id</span>.<span class="ident">dst</span> <span class="op">==</span> <span class="kw-2">*</span><span class="ident">l</span>)
                    .<span class="ident">unwrap</span>();
                <span class="kw">if</span> <span class="ident">src_order</span> <span class="op">==</span> <span class="ident">dst_order</span> {
                    <span class="ident">turns</span>.<span class="ident">push</span>(<span class="ident">t</span>);
                }
            }
            <span class="kw">continue</span>;
        }

        <span class="comment">// If src &lt; dst and src isn&#39;t 1, then one source lane gets to access multiple destination</span>
        <span class="comment">// lanes. For now, just give up figuring this out, and allow all combinations.</span>
        <span class="comment">//</span>
        <span class="comment">// TODO https://wiki.openstreetmap.org/wiki/Relation:connectivity may have hints about a</span>
        <span class="comment">// better algorithm.</span>
        <span class="kw">if</span> <span class="ident">num_src_lanes</span> <span class="op">&lt;</span> <span class="ident">num_dst_lanes</span> {
            <span class="ident">turns</span>.<span class="ident">extend</span>(<span class="ident">group</span>);
            <span class="kw">continue</span>;
        }

        <span class="comment">// If we get here, then multiple source lanes are forced to merge into one destination</span>
        <span class="comment">// lane.</span>
        <span class="comment">//</span>
        <span class="comment">// Just kind of give up on these cases for now, and fall-back to only allowing the leftmost</span>
        <span class="comment">// or rightmost source lane to make these turns.</span>
        <span class="comment">//</span>
        <span class="comment">// That left or rightmost lane can turn into all lanes on the destination road. Tempting to</span>
        <span class="comment">// remove this, but it may remove some valid U-turn movements (like on Mercer).</span>
        <span class="kw">let</span> <span class="ident">road</span> <span class="op">=</span> <span class="ident">map</span>.<span class="ident">get_parent</span>(<span class="ident">group</span>[<span class="number">0</span>].<span class="ident">id</span>.<span class="ident">src</span>);
        <span class="kw">let</span> <span class="ident">src</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">turn_type</span> <span class="op">==</span> <span class="ident">TurnType::Right</span> {
            <span class="ident">group</span>
                .<span class="ident">iter</span>()
                .<span class="ident">max_by_key</span>(<span class="op">|</span><span class="ident">t</span><span class="op">|</span> <span class="ident">road</span>.<span class="ident">dir_and_offset</span>(<span class="ident">t</span>.<span class="ident">id</span>.<span class="ident">src</span>).<span class="number">1</span>)
                .<span class="ident">unwrap</span>()
                .<span class="ident">id</span>
                .<span class="ident">src</span>
        } <span class="kw">else</span> <span class="kw">if</span> <span class="ident">turn_type</span> <span class="op">==</span> <span class="ident">TurnType::Left</span> {
            <span class="ident">group</span>
                .<span class="ident">iter</span>()
                .<span class="ident">min_by_key</span>(<span class="op">|</span><span class="ident">t</span><span class="op">|</span> <span class="ident">road</span>.<span class="ident">dir_and_offset</span>(<span class="ident">t</span>.<span class="ident">id</span>.<span class="ident">src</span>).<span class="number">1</span>)
                .<span class="ident">unwrap</span>()
                .<span class="ident">id</span>
                .<span class="ident">src</span>
        } <span class="kw">else</span> {
            <span class="macro">unreachable!</span>()
        };
        <span class="kw">for</span> <span class="ident">t</span> <span class="kw">in</span> <span class="ident">group</span> {
            <span class="kw">if</span> <span class="ident">t</span>.<span class="ident">id</span>.<span class="ident">src</span> <span class="op">==</span> <span class="ident">src</span> {
                <span class="ident">turns</span>.<span class="ident">push</span>(<span class="ident">t</span>);
            }
        }
    }
    <span class="ident">turns</span>
}

<span class="kw">fn</span> <span class="ident">turn_type_from_angles</span>(<span class="ident">from</span>: <span class="ident">Angle</span>, <span class="ident">to</span>: <span class="ident">Angle</span>) -&gt; <span class="ident">TurnType</span> {
    <span class="kw">let</span> <span class="ident">diff</span> <span class="op">=</span> <span class="ident">from</span>.<span class="ident">simple_shortest_rotation_towards</span>(<span class="ident">to</span>);
    <span class="comment">// This is a pretty arbitrary parameter, but a difference of 30 degrees seems reasonable for</span>
    <span class="comment">// some observed cases.</span>
    <span class="kw">if</span> <span class="ident">diff</span>.<span class="ident">abs</span>() <span class="op">&lt;</span> <span class="number">30.0</span> {
        <span class="ident">TurnType::Straight</span>
    } <span class="kw">else</span> <span class="kw">if</span> <span class="ident">diff</span>.<span class="ident">abs</span>() <span class="op">&gt;</span> <span class="number">135.0</span> {
        <span class="ident">TurnType::UTurn</span>
    } <span class="kw">else</span> <span class="kw">if</span> <span class="ident">diff</span> <span class="op">&lt;</span> <span class="number">0.0</span> {
        <span class="comment">// Clockwise rotation</span>
        <span class="ident">TurnType::Right</span>
    } <span class="kw">else</span> {
        <span class="comment">// Counter-clockwise rotation</span>
        <span class="ident">TurnType::Left</span>
    }
}

<span class="kw">fn</span> <span class="ident">expected_turn_types_for_four_way</span>(
    <span class="ident">i</span>: <span class="kw-2">&amp;</span><span class="ident">Intersection</span>,
    <span class="ident">map</span>: <span class="kw-2">&amp;</span><span class="ident">Map</span>,
) -&gt; <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">HashMap</span><span class="op">&lt;</span>(<span class="ident">RoadID</span>, <span class="ident">RoadID</span>), <span class="ident">TurnType</span><span class="op">&gt;</span><span class="op">&gt;</span> {
    <span class="kw">let</span> <span class="ident">roads</span> <span class="op">=</span> <span class="ident">i</span>.<span class="ident">get_sorted_incoming_roads</span>(<span class="ident">map</span>);
    <span class="kw">if</span> <span class="ident">roads</span>.<span class="ident">len</span>() <span class="op">!</span><span class="op">=</span> <span class="number">4</span> {
        <span class="kw">return</span> <span class="prelude-val">None</span>;
    }

    <span class="comment">// Just based on relative ordering around the intersection, turns (from road, to road, should</span>
    <span class="comment">// have this type)</span>
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">expected_turn_types</span>: <span class="ident">HashMap</span><span class="op">&lt;</span>(<span class="ident">RoadID</span>, <span class="ident">RoadID</span>), <span class="ident">TurnType</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">HashMap::new</span>();
    <span class="kw">for</span> (<span class="ident">offset</span>, <span class="ident">turn_type</span>) <span class="kw">in</span> [
        (<span class="number">1</span>, <span class="ident">TurnType::Left</span>),
        (<span class="number">2</span>, <span class="ident">TurnType::Straight</span>),
        (<span class="number">3</span>, <span class="ident">TurnType::Right</span>),
    ] {
        <span class="kw">for</span> <span class="ident">from_idx</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">roads</span>.<span class="ident">len</span>() {
            <span class="kw">let</span> <span class="ident">to</span> <span class="op">=</span> <span class="kw-2">*</span><span class="ident">abstutil::wraparound_get</span>(<span class="kw-2">&amp;</span><span class="ident">roads</span>, (<span class="ident">from_idx</span> <span class="kw">as</span> <span class="ident">isize</span>) <span class="op">+</span> <span class="ident">offset</span>);
            <span class="ident">expected_turn_types</span>.<span class="ident">insert</span>((<span class="ident">roads</span>[<span class="ident">from_idx</span>], <span class="ident">to</span>), <span class="ident">turn_type</span>);
        }
    }
    <span class="prelude-val">Some</span>(<span class="ident">expected_turn_types</span>)
}
</code></pre></div>
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