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</pre><pre class="rust"><code><span class="doccomment">//! Some helpers for working with fast_paths.</span>

<span class="kw">use</span> <span class="ident">std::collections::BTreeMap</span>;
<span class="kw">use</span> <span class="ident">std::fmt::Debug</span>;

<span class="kw">use</span> <span class="ident">fast_paths</span>::{<span class="ident">InputGraph</span>, <span class="ident">NodeId</span>};
<span class="kw">use</span> <span class="ident">serde</span>::{<span class="ident">Deserialize</span>, <span class="ident">Deserializer</span>, <span class="ident">Serialize</span>};

<span class="doccomment">/// A bidirectional mapping between fast_paths NodeId and some custom ID type.</span>
<span class="comment">// TODO Upstream this in fast_paths when this is more solid.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Serialize</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">NodeMap</span><span class="op">&lt;</span><span class="ident">T</span>: <span class="ident">Copy</span> <span class="op">+</span> <span class="ident">Ord</span> <span class="op">+</span> <span class="ident">Debug</span> <span class="op">+</span> <span class="ident">Serialize</span><span class="op">&gt;</span> {
    <span class="comment">// These two fields are redundant and large, so don&#39;t serialize the bigger one, to cut down</span>
    <span class="comment">// file size.</span>
    <span class="attribute">#[<span class="ident">serde</span>(<span class="ident">skip_serializing</span>)]</span>
    <span class="ident">node_to_id</span>: <span class="ident">BTreeMap</span><span class="op">&lt;</span><span class="ident">T</span>, <span class="ident">NodeId</span><span class="op">&gt;</span>,
    <span class="ident">id_to_node</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">T</span><span class="op">&gt;</span>,
}

<span class="kw">impl</span><span class="op">&lt;</span><span class="ident">T</span>: <span class="ident">Copy</span> <span class="op">+</span> <span class="ident">Ord</span> <span class="op">+</span> <span class="ident">Debug</span> <span class="op">+</span> <span class="ident">Serialize</span><span class="op">&gt;</span> <span class="ident">NodeMap</span><span class="op">&lt;</span><span class="ident">T</span><span class="op">&gt;</span> {
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>() -&gt; <span class="ident">NodeMap</span><span class="op">&lt;</span><span class="ident">T</span><span class="op">&gt;</span> {
        <span class="ident">NodeMap</span> {
            <span class="ident">node_to_id</span>: <span class="ident">BTreeMap::new</span>(),
            <span class="ident">id_to_node</span>: <span class="ident">Vec::new</span>(),
        }
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">get_or_insert</span>(<span class="kw-2">&amp;mut</span> <span class="self">self</span>, <span class="ident">node</span>: <span class="ident">T</span>) -&gt; <span class="ident">NodeId</span> {
        <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">id</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">node_to_id</span>.<span class="ident">get</span>(<span class="kw-2">&amp;</span><span class="ident">node</span>) {
            <span class="kw">return</span> <span class="kw-2">*</span><span class="ident">id</span>;
        }
        <span class="kw">let</span> <span class="ident">id</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">id_to_node</span>.<span class="ident">len</span>();
        <span class="self">self</span>.<span class="ident">node_to_id</span>.<span class="ident">insert</span>(<span class="ident">node</span>, <span class="ident">id</span>);
        <span class="self">self</span>.<span class="ident">id_to_node</span>.<span class="ident">push</span>(<span class="ident">node</span>);
        <span class="ident">id</span>
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">get</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">node</span>: <span class="ident">T</span>) -&gt; <span class="ident">NodeId</span> {
        <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">id</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">node_to_id</span>.<span class="ident">get</span>(<span class="kw-2">&amp;</span><span class="ident">node</span>) {
            <span class="kw-2">*</span><span class="ident">id</span>
        } <span class="kw">else</span> {
            <span class="macro">panic!</span>(<span class="string">&quot;{:?} not in NodeMap&quot;</span>, <span class="ident">node</span>);
        }
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">translate_id</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">id</span>: <span class="ident">usize</span>) -&gt; <span class="ident">T</span> {
        <span class="self">self</span>.<span class="ident">id_to_node</span>[<span class="ident">id</span>]
    }

    <span class="doccomment">/// Call this after filling out the input graph, right before preparation.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">guarantee_node_ordering</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">input_graph</span>: <span class="kw-2">&amp;mut</span> <span class="ident">InputGraph</span>) {
        <span class="comment">// The fast_paths implementation will trim out the last nodes in the input graph if there</span>
        <span class="comment">// are no edges involving them:</span>
        <span class="comment">// https://github.com/easbar/fast_paths/blob/fdb65f25c5485c9c74c1b3cbe66d829eea81b14b/src/input_graph.rs#L151</span>
        <span class="comment">//</span>
        <span class="comment">// We sometimes add nodes that aren&#39;t used yet, so that we can reuse the same node ordering</span>
        <span class="comment">// later. Detect if the last node isn&#39;t used.</span>
        <span class="kw">let</span> <span class="ident">last_node</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">id_to_node</span>.<span class="ident">len</span>() <span class="op">-</span> <span class="number">1</span>;
        <span class="ident">input_graph</span>.<span class="ident">freeze</span>();
        <span class="kw">for</span> <span class="ident">edge</span> <span class="kw">in</span> <span class="ident">input_graph</span>.<span class="ident">get_edges</span>() {
            <span class="kw">if</span> <span class="ident">edge</span>.<span class="ident">from</span> <span class="op">==</span> <span class="ident">last_node</span> <span class="op">|</span><span class="op">|</span> <span class="ident">edge</span>.<span class="ident">to</span> <span class="op">==</span> <span class="ident">last_node</span> {
                <span class="comment">// The last node is used, so we&#39;re fine</span>
                <span class="ident">input_graph</span>.<span class="ident">thaw</span>();
                <span class="kw">return</span>;
            }
        }
        <span class="ident">input_graph</span>.<span class="ident">thaw</span>();

        <span class="comment">// Add a dummy edge from this unused node to any arbitrary node (namely the first), to</span>
        <span class="comment">// prevent it from getting trimmed out. Since no path will start or end from this unused</span>
        <span class="comment">// node, this won&#39;t affect resulting paths.</span>
        <span class="kw">let</span> <span class="ident">first_node</span> <span class="op">=</span> <span class="number">0</span>;
        <span class="ident">input_graph</span>.<span class="ident">add_edge</span>(<span class="ident">last_node</span>, <span class="ident">first_node</span>, <span class="number">1</span>);
    }
}

<span class="comment">// A serialized NodeMap has this form in JSON. Use this to deserialize.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Deserialize</span>)]</span>
<span class="kw">struct</span> <span class="ident">InnerNodeMap</span><span class="op">&lt;</span><span class="ident">T</span>: <span class="ident">Copy</span> <span class="op">+</span> <span class="ident">Ord</span> <span class="op">+</span> <span class="ident">Debug</span><span class="op">&gt;</span> {
    <span class="ident">id_to_node</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">T</span><span class="op">&gt;</span>,
}

<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">deserialize_nodemap</span><span class="op">&lt;</span>
    <span class="lifetime">&#39;de</span>,
    <span class="ident">D</span>: <span class="ident">Deserializer</span><span class="op">&lt;</span><span class="lifetime">&#39;de</span><span class="op">&gt;</span>,
    <span class="ident">T</span>: <span class="ident">Deserialize</span><span class="op">&lt;</span><span class="lifetime">&#39;de</span><span class="op">&gt;</span> <span class="op">+</span> <span class="ident">Copy</span> <span class="op">+</span> <span class="ident">Ord</span> <span class="op">+</span> <span class="ident">Debug</span> <span class="op">+</span> <span class="ident">Serialize</span>,
<span class="op">&gt;</span>(
    <span class="ident">d</span>: <span class="ident">D</span>,
) -&gt; <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">NodeMap</span><span class="op">&lt;</span><span class="ident">T</span><span class="op">&gt;</span>, <span class="ident">D::Error</span><span class="op">&gt;</span> {
    <span class="kw">let</span> <span class="ident">inner</span> <span class="op">=</span> <span class="op">&lt;</span><span class="ident">InnerNodeMap</span><span class="op">&lt;</span><span class="ident">T</span><span class="op">&gt;</span><span class="op">&gt;</span><span class="ident">::deserialize</span>(<span class="ident">d</span>)<span class="question-mark">?</span>;
    <span class="kw">let</span> <span class="ident">id_to_node</span> <span class="op">=</span> <span class="ident">inner</span>.<span class="ident">id_to_node</span>;
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">node_to_id</span> <span class="op">=</span> <span class="ident">BTreeMap::new</span>();
    <span class="kw">for</span> (<span class="ident">id</span>, <span class="ident">node</span>) <span class="kw">in</span> <span class="ident">id_to_node</span>.<span class="ident">iter</span>().<span class="ident">enumerate</span>() {
        <span class="ident">node_to_id</span>.<span class="ident">insert</span>(<span class="kw-2">*</span><span class="ident">node</span>, <span class="ident">id</span>);
    }

    <span class="prelude-val">Ok</span>(<span class="ident">NodeMap</span> {
        <span class="ident">node_to_id</span>,
        <span class="ident">id_to_node</span>,
    })
}
</code></pre></div>
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