<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `map_gui&#x2F;src&#x2F;tools&#x2F;url.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>url.rs - source</title><link rel="stylesheet" type="text/css" href="../../../normalize.css"><link rel="stylesheet" type="text/css" href="../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../../light.css"  id="themeStyle"><link rel="stylesheet" type="text/css" href="../../../dark.css" disabled ><link rel="stylesheet" type="text/css" href="../../../ayu.css" disabled ><script id="default-settings" ></script><script src="../../../storage.js"></script><script src="../../../crates.js"></script><noscript><link rel="stylesheet" href="../../../noscript.css"></noscript><link rel="icon" type="image/svg+xml" href="../../../favicon.svg"><link rel="alternate icon" type="image/png" href="../../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../../favicon-32x32.png"><style type="text/css">#crate-search{background-image:url("../../../down-arrow.svg");}</style></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu" role="button">&#9776;</div><a href='../../../map_gui/index.html'><div class='logo-container rust-logo'><img src='../../../rust-logo.png' alt='logo'></div></a></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!" aria-haspopup="menu" title="themes"><img width="18" height="18" alt="Pick another theme!" src="../../../brush.svg"></button><div id="theme-choices" role="menu"></div></div><nav class="sub"><form class="search-form"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input"name="search" disabled autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"></div><button type="button" id="help-button" title="help">?</button><a id="settings-menu" href="../../../settings.html" title="settings"><img width="18" height="18" alt="Change settings" src="../../../wheel.svg"></a></div></form></nav><section id="main" class="content"><div class="example-wrap"><pre class="line-numbers"><span id="1">  1</span>
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</pre><pre class="rust">
<span class="kw">use</span> <span class="ident">anyhow::Result</span>;

<span class="kw">use</span> <span class="ident">geom</span>::{<span class="ident">GPSBounds</span>, <span class="ident">LonLat</span>, <span class="ident">Pt2D</span>};
<span class="kw">use</span> <span class="ident">widgetry::EventCtx</span>;

<span class="doccomment">/// Utilities for reflecting the current map and viewport in the URL on the web. No effect on</span>
<span class="doccomment">/// native.</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">URLManager</span>;

<span class="kw">impl</span> <span class="ident">URLManager</span> {
    <span class="doccomment">/// This does nothing on native. On web, it modifies the current URL to change the first free</span>
    <span class="doccomment">/// parameter in the HTTP GET params to the specified value, adding it if needed.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">update_url_free_param</span>(<span class="ident">free_param</span>: <span class="ident">String</span>) {
        <span class="ident">must_update_url</span>(<span class="ident">Box::new</span>(<span class="kw">move</span> <span class="op">|</span><span class="ident">url</span><span class="op">|</span> <span class="ident">change_url_free_param</span>(<span class="ident">url</span>, <span class="kw-2">&amp;</span><span class="ident">free_param</span>)))
    }

    <span class="doccomment">/// This does nothing on native. On web, it modifies the current URL to change the first named</span>
    <span class="doccomment">/// parameter in the HTTP GET params to the specified value, adding it if needed.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">update_url_param</span>(<span class="ident">key</span>: <span class="ident">String</span>, <span class="ident">value</span>: <span class="ident">String</span>) {
        <span class="ident">must_update_url</span>(<span class="ident">Box::new</span>(<span class="kw">move</span> <span class="op">|</span><span class="ident">url</span><span class="op">|</span> <span class="ident">change_url_param</span>(<span class="ident">url</span>, <span class="kw-2">&amp;</span><span class="ident">key</span>, <span class="kw-2">&amp;</span><span class="ident">value</span>)))
    }

    <span class="doccomment">/// This does nothing on native. On web, it modifies the current URL to set --cam to an</span>
    <span class="doccomment">/// OSM-style `zoom/lat/lon` string</span>
    <span class="doccomment">/// (https://wiki.openstreetmap.org/wiki/Browsing#Other_URL_tricks) based on the current</span>
    <span class="doccomment">/// viewport.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">update_url_cam</span>(<span class="ident">ctx</span>: <span class="kw-2">&amp;</span><span class="ident">EventCtx</span>, <span class="ident">gps_bounds</span>: <span class="kw-2">&amp;</span><span class="ident">GPSBounds</span>) {
        <span class="kw">let</span> <span class="ident">center</span> <span class="op">=</span> <span class="ident">ctx</span>.<span class="ident">canvas</span>.<span class="ident">center_to_map_pt</span>().<span class="ident">to_gps</span>(<span class="ident">gps_bounds</span>);

        <span class="comment">// To calculate zoom, just solve for the inverse of the code in parse_center_camera.</span>
        <span class="kw">let</span> <span class="ident">earth_circumference_equator</span> <span class="op">=</span> <span class="number">40_075_016.686</span>;
        <span class="kw">let</span> <span class="ident">log_arg</span> <span class="op">=</span>
            <span class="ident">earth_circumference_equator</span> <span class="op">*</span> <span class="ident">center</span>.<span class="ident">y</span>().<span class="ident">to_radians</span>().<span class="ident">cos</span>() <span class="op">*</span> <span class="ident">ctx</span>.<span class="ident">canvas</span>.<span class="ident">cam_zoom</span>;
        <span class="kw">let</span> <span class="ident">zoom_lvl</span> <span class="op">=</span> <span class="ident">log_arg</span>.<span class="ident">log2</span>() <span class="op">-</span> <span class="number">8.0</span>;

        <span class="comment">// Trim precision</span>
        <span class="kw">let</span> <span class="ident">cam</span> <span class="op">=</span> <span class="macro">format!</span>(<span class="string">&quot;{:.2}/{:.5}/{:.5}&quot;</span>, <span class="ident">zoom_lvl</span>, <span class="ident">center</span>.<span class="ident">y</span>(), <span class="ident">center</span>.<span class="ident">x</span>());

        <span class="ident">must_update_url</span>(<span class="ident">Box::new</span>(<span class="kw">move</span> <span class="op">|</span><span class="ident">url</span><span class="op">|</span> <span class="ident">change_url_param</span>(<span class="ident">url</span>, <span class="string">&quot;--cam&quot;</span>, <span class="kw-2">&amp;</span><span class="ident">cam</span>)))
    }

    <span class="doccomment">/// Parse an OSM-style `zoom/lat/lon` string</span>
    <span class="doccomment">/// (https://wiki.openstreetmap.org/wiki/Browsing#Other_URL_tricks), changing the canvas</span>
    <span class="doccomment">/// appropriately. Returns true upon success.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">change_camera</span>(<span class="ident">ctx</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">EventCtx</span>, <span class="ident">raw</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="kw-2">&amp;</span><span class="ident">String</span><span class="op">&gt;</span>, <span class="ident">gps_bounds</span>: <span class="kw-2">&amp;</span><span class="ident">GPSBounds</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">bool</span> {
        <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>((<span class="ident">pt</span>, <span class="ident">zoom</span>)) <span class="op">=</span>
            <span class="ident">raw</span>.<span class="ident">and_then</span>(<span class="op">|</span><span class="ident">raw</span><span class="op">|</span> <span class="ident">URLManager::parse_center_camera</span>(<span class="ident">raw</span>, <span class="ident">gps_bounds</span>))
        {
            <span class="ident">ctx</span>.<span class="ident">canvas</span>.<span class="ident">cam_zoom</span> <span class="op">=</span> <span class="ident">zoom</span>;
            <span class="ident">ctx</span>.<span class="ident">canvas</span>.<span class="ident">center_on_map_pt</span>(<span class="ident">pt</span>);
            <span class="bool-val">true</span>
        } <span class="kw">else</span> {
            <span class="bool-val">false</span>
        }
    }

    <span class="doccomment">/// Parse an OSM-style `zoom/lat/lon` string</span>
    <span class="doccomment">/// (https://wiki.openstreetmap.org/wiki/Browsing#Other_URL_tricks), returning the map point to</span>
    <span class="doccomment">/// center on and the camera zoom.</span>
    <span class="kw">fn</span> <span class="ident">parse_center_camera</span>(<span class="ident">raw</span>: <span class="kw-2">&amp;</span><span class="ident">str</span>, <span class="ident">gps_bounds</span>: <span class="kw-2">&amp;</span><span class="ident">GPSBounds</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Option</span><span class="op">&lt;</span>(<span class="ident">Pt2D</span>, <span class="ident">f64</span>)<span class="op">&gt;</span> {
        <span class="kw">let</span> <span class="ident">parts</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="kw-2">&amp;</span><span class="ident">str</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">raw</span>.<span class="ident">split</span>(<span class="string">&#39;/&#39;</span>).<span class="ident">collect</span>();
        <span class="kw">if</span> <span class="ident">parts</span>.<span class="ident">len</span>() <span class="op">!</span><span class="op">=</span> <span class="number">3</span> {
            <span class="kw">return</span> <span class="prelude-val">None</span>;
        }
        <span class="kw">let</span> <span class="ident">zoom_lvl</span> <span class="op">=</span> <span class="ident">parts</span>[<span class="number">0</span>].<span class="ident">parse</span>::<span class="op">&lt;</span><span class="ident">f64</span><span class="op">&gt;</span>().<span class="ident">ok</span>()<span class="question-mark">?</span>;
        <span class="kw">let</span> <span class="ident">lat</span> <span class="op">=</span> <span class="ident">parts</span>[<span class="number">1</span>].<span class="ident">parse</span>::<span class="op">&lt;</span><span class="ident">f64</span><span class="op">&gt;</span>().<span class="ident">ok</span>()<span class="question-mark">?</span>;
        <span class="kw">let</span> <span class="ident">lon</span> <span class="op">=</span> <span class="ident">parts</span>[<span class="number">2</span>].<span class="ident">parse</span>::<span class="op">&lt;</span><span class="ident">f64</span><span class="op">&gt;</span>().<span class="ident">ok</span>()<span class="question-mark">?</span>;
        <span class="kw">let</span> <span class="ident">gps</span> <span class="op">=</span> <span class="ident">LonLat::new</span>(<span class="ident">lon</span>, <span class="ident">lat</span>);
        <span class="kw">if</span> <span class="op">!</span><span class="ident">gps_bounds</span>.<span class="ident">contains</span>(<span class="ident">gps</span>) {
            <span class="kw">return</span> <span class="prelude-val">None</span>;
        }
        <span class="kw">let</span> <span class="ident">pt</span> <span class="op">=</span> <span class="ident">gps</span>.<span class="ident">to_pt</span>(<span class="ident">gps_bounds</span>);

        <span class="comment">// To figure out zoom, first calculate horizontal meters per pixel, using the formula from</span>
        <span class="comment">// https://wiki.openstreetmap.org/wiki/Zoom_levels.</span>
        <span class="kw">let</span> <span class="ident">earth_circumference_equator</span> <span class="op">=</span> <span class="number">40_075_016.686</span>;
        <span class="kw">let</span> <span class="ident">horiz_meters_per_pixel</span> <span class="op">=</span>
            <span class="ident">earth_circumference_equator</span> <span class="op">*</span> <span class="ident">gps</span>.<span class="ident">y</span>().<span class="ident">to_radians</span>().<span class="ident">cos</span>() <span class="op">/</span> <span class="number">2.0_f64</span>.<span class="ident">powf</span>(<span class="ident">zoom_lvl</span> <span class="op">+</span> <span class="number">8.0</span>);

        <span class="comment">// So this is the width in meters that should cover our screen</span>
        <span class="comment">// let horiz_meters_per_screen = ctx.canvas.window_width * horiz_meters_per_pixel;</span>
        <span class="comment">// Now we want to make screen_to_map(the top-right corner of the screen) =</span>
        <span class="comment">// horiz_meters_per_screen. Easy algebra:</span>
        <span class="comment">// let cam_zoom = ctx.canvas.window_width / horiz_meters_per_screen;</span>

        <span class="comment">// But actually, the algebra shows we don&#39;t even need window_width. Easy!</span>
        <span class="kw">let</span> <span class="ident">cam_zoom</span> <span class="op">=</span> <span class="number">1.0</span> <span class="op">/</span> <span class="ident">horiz_meters_per_pixel</span>;

        <span class="prelude-val">Some</span>((<span class="ident">pt</span>, <span class="ident">cam_zoom</span>))
    }
}

<span class="kw">fn</span> <span class="ident">must_update_url</span>(<span class="ident">transform</span>: <span class="ident">Box</span><span class="op">&lt;</span><span class="kw">dyn</span> <span class="ident">Fn</span>(<span class="ident">String</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">String</span><span class="op">&gt;</span>) {
    <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Err</span>(<span class="ident">err</span>) <span class="op">=</span> <span class="ident">update_url</span>(<span class="ident">transform</span>) {
        <span class="macro">warn!</span>(<span class="string">&quot;Couldn&#39;t update URL: {}&quot;</span>, <span class="ident">err</span>);
    }
}

<span class="attribute">#[<span class="ident">allow</span>(<span class="ident">unused_variables</span>)]</span>
<span class="kw">fn</span> <span class="ident">update_url</span>(<span class="ident">transform</span>: <span class="ident">Box</span><span class="op">&lt;</span><span class="kw">dyn</span> <span class="ident">Fn</span>(<span class="ident">String</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">String</span><span class="op">&gt;</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span>()<span class="op">&gt;</span> {
    <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">target_arch</span> <span class="op">=</span> <span class="string">&quot;wasm32&quot;</span>)]</span>
    {
        <span class="kw">let</span> <span class="ident">window</span> <span class="op">=</span> <span class="ident">web_sys::window</span>().<span class="ident">ok_or</span>(<span class="macro">anyhow!</span>(<span class="string">&quot;no window?&quot;</span>))<span class="question-mark">?</span>;
        <span class="kw">let</span> <span class="ident">url</span> <span class="op">=</span> <span class="ident">window</span>.<span class="ident">location</span>().<span class="ident">href</span>().<span class="ident">map_err</span>(<span class="op">|</span><span class="ident">err</span><span class="op">|</span> {
            <span class="macro">anyhow!</span>(<span class="ident">err</span>
                .<span class="ident">as_string</span>()
                .<span class="ident">unwrap_or</span>(<span class="string">&quot;window.location.href failed&quot;</span>.<span class="ident">to_string</span>()))
        })<span class="question-mark">?</span>;
        <span class="kw">let</span> <span class="ident">new_url</span> <span class="op">=</span> (<span class="ident">transform</span>)(<span class="ident">url</span>);

        <span class="comment">// Setting window.location.href may seem like the obvious thing to do, but that actually</span>
        <span class="comment">// refreshes the page. This method just changes the URL and doesn&#39;t mess up history. See</span>
        <span class="comment">// https://developer.mozilla.org/en-US/docs/Web/API/History_API/Working_with_the_History_API.</span>
        <span class="kw">let</span> <span class="ident">history</span> <span class="op">=</span> <span class="ident">window</span>.<span class="ident">history</span>().<span class="ident">map_err</span>(<span class="op">|</span><span class="ident">err</span><span class="op">|</span> {
            <span class="macro">anyhow!</span>(<span class="ident">err</span>
                .<span class="ident">as_string</span>()
                .<span class="ident">unwrap_or</span>(<span class="string">&quot;window.history failed&quot;</span>.<span class="ident">to_string</span>()))
        })<span class="question-mark">?</span>;
        <span class="ident">history</span>
            .<span class="ident">replace_state_with_url</span>(<span class="kw-2">&amp;</span><span class="ident">wasm_bindgen::JsValue::NULL</span>, <span class="string">&quot;&quot;</span>, <span class="prelude-val">Some</span>(<span class="kw-2">&amp;</span><span class="ident">new_url</span>))
            .<span class="ident">map_err</span>(<span class="op">|</span><span class="ident">err</span><span class="op">|</span> {
                <span class="macro">anyhow!</span>(<span class="ident">err</span>
                    .<span class="ident">as_string</span>()
                    .<span class="ident">unwrap_or</span>(<span class="string">&quot;window.history.replace_state failed&quot;</span>.<span class="ident">to_string</span>()))
            })<span class="question-mark">?</span>;
    }
    <span class="prelude-val">Ok</span>(())
}

<span class="kw">fn</span> <span class="ident">change_url_free_param</span>(<span class="ident">url</span>: <span class="ident">String</span>, <span class="ident">free_param</span>: <span class="kw-2">&amp;</span><span class="ident">str</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">String</span> {
    <span class="comment">// The URL parsing crates I checked had lots of dependencies and didn&#39;t even expose such a nice</span>
    <span class="comment">// API for doing this anyway.</span>
    <span class="kw">let</span> <span class="ident">url_parts</span> <span class="op">=</span> <span class="ident">url</span>.<span class="ident">split</span>(<span class="string">&#39;?&#39;</span>).<span class="ident">collect</span>::<span class="op">&lt;</span><span class="ident">Vec</span><span class="op">&lt;</span><span class="kw">_</span><span class="op">&gt;</span><span class="op">&gt;</span>();
    <span class="kw">if</span> <span class="ident">url_parts</span>.<span class="ident">len</span>() <span class="op">=</span><span class="op">=</span> <span class="number">1</span> {
        <span class="kw">return</span> <span class="macro">format!</span>(<span class="string">&quot;{}?{}&quot;</span>, <span class="ident">url</span>, <span class="ident">free_param</span>);
    }
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">query_params</span> <span class="op">=</span> <span class="ident">String::new</span>();
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">found_free</span> <span class="op">=</span> <span class="bool-val">false</span>;
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">first</span> <span class="op">=</span> <span class="bool-val">true</span>;
    <span class="kw">for</span> <span class="ident">x</span> <span class="kw">in</span> <span class="ident">url_parts</span>[<span class="number">1</span>].<span class="ident">split</span>(<span class="string">&#39;&amp;&#39;</span>) {
        <span class="kw">if</span> <span class="op">!</span><span class="ident">first</span> {
            <span class="ident">query_params</span>.<span class="ident">push</span>(<span class="string">&#39;&amp;&#39;</span>);
        }
        <span class="ident">first</span> <span class="op">=</span> <span class="bool-val">false</span>;

        <span class="kw">if</span> <span class="ident">x</span>.<span class="ident">starts_with</span>(<span class="string">&quot;--&quot;</span>) {
            <span class="ident">query_params</span>.<span class="ident">push_str</span>(<span class="ident">x</span>);
        } <span class="kw">else</span> <span class="kw">if</span> <span class="op">!</span><span class="ident">found_free</span> {
            <span class="comment">// Replace the first free parameter</span>
            <span class="ident">query_params</span>.<span class="ident">push_str</span>(<span class="ident">free_param</span>);
            <span class="ident">found_free</span> <span class="op">=</span> <span class="bool-val">true</span>;
        } <span class="kw">else</span> {
            <span class="ident">query_params</span>.<span class="ident">push_str</span>(<span class="ident">x</span>);
        }
    }
    <span class="kw">if</span> <span class="op">!</span><span class="ident">found_free</span> {
        <span class="kw">if</span> <span class="op">!</span><span class="ident">first</span> {
            <span class="ident">query_params</span>.<span class="ident">push</span>(<span class="string">&#39;&amp;&#39;</span>);
        }
        <span class="ident">query_params</span>.<span class="ident">push_str</span>(<span class="ident">free_param</span>);
    }

    <span class="macro">format!</span>(<span class="string">&quot;{}?{}&quot;</span>, <span class="ident">url_parts</span>[<span class="number">0</span>], <span class="ident">query_params</span>)
}

<span class="kw">fn</span> <span class="ident">change_url_param</span>(<span class="ident">url</span>: <span class="ident">String</span>, <span class="ident">key</span>: <span class="kw-2">&amp;</span><span class="ident">str</span>, <span class="ident">value</span>: <span class="kw-2">&amp;</span><span class="ident">str</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">String</span> {
    <span class="comment">// The URL parsing crates I checked had lots of dependencies and didn&#39;t even expose such a nice</span>
    <span class="comment">// API for doing this anyway.</span>
    <span class="kw">let</span> <span class="ident">url_parts</span> <span class="op">=</span> <span class="ident">url</span>.<span class="ident">split</span>(<span class="string">&#39;?&#39;</span>).<span class="ident">collect</span>::<span class="op">&lt;</span><span class="ident">Vec</span><span class="op">&lt;</span><span class="kw">_</span><span class="op">&gt;</span><span class="op">&gt;</span>();
    <span class="kw">if</span> <span class="ident">url_parts</span>.<span class="ident">len</span>() <span class="op">=</span><span class="op">=</span> <span class="number">1</span> {
        <span class="kw">return</span> <span class="macro">format!</span>(<span class="string">&quot;{}?{}={}&quot;</span>, <span class="ident">url</span>, <span class="ident">key</span>, <span class="ident">value</span>);
    }
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">query_params</span> <span class="op">=</span> <span class="ident">String::new</span>();
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">found_key</span> <span class="op">=</span> <span class="bool-val">false</span>;
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">first</span> <span class="op">=</span> <span class="bool-val">true</span>;
    <span class="kw">for</span> <span class="ident">x</span> <span class="kw">in</span> <span class="ident">url_parts</span>[<span class="number">1</span>].<span class="ident">split</span>(<span class="string">&#39;&amp;&#39;</span>) {
        <span class="kw">if</span> <span class="op">!</span><span class="ident">first</span> {
            <span class="ident">query_params</span>.<span class="ident">push</span>(<span class="string">&#39;&amp;&#39;</span>);
        }
        <span class="ident">first</span> <span class="op">=</span> <span class="bool-val">false</span>;

        <span class="kw">if</span> <span class="ident">x</span>.<span class="ident">starts_with</span>(<span class="ident">key</span>) {
            <span class="ident">query_params</span>.<span class="ident">push_str</span>(<span class="kw-2">&amp;</span><span class="macro">format!</span>(<span class="string">&quot;{}={}&quot;</span>, <span class="ident">key</span>, <span class="ident">value</span>));
            <span class="ident">found_key</span> <span class="op">=</span> <span class="bool-val">true</span>;
        } <span class="kw">else</span> {
            <span class="ident">query_params</span>.<span class="ident">push_str</span>(<span class="ident">x</span>);
        }
    }
    <span class="kw">if</span> <span class="op">!</span><span class="ident">found_key</span> {
        <span class="kw">if</span> <span class="op">!</span><span class="ident">first</span> {
            <span class="ident">query_params</span>.<span class="ident">push</span>(<span class="string">&#39;&amp;&#39;</span>);
        }
        <span class="ident">query_params</span>.<span class="ident">push_str</span>(<span class="kw-2">&amp;</span><span class="macro">format!</span>(<span class="string">&quot;{}={}&quot;</span>, <span class="ident">key</span>, <span class="ident">value</span>));
    }

    <span class="macro">format!</span>(<span class="string">&quot;{}?{}&quot;</span>, <span class="ident">url_parts</span>[<span class="number">0</span>], <span class="ident">query_params</span>)
}

<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span>
<span class="kw">mod</span> <span class="ident">tests</span> {
    <span class="attribute">#[<span class="ident">test</span>]</span>
    <span class="kw">fn</span> <span class="ident">test_change_url_free_param</span>() {
        <span class="kw">use</span> <span class="kw">super</span><span class="ident">::change_url_free_param</span>;

        <span class="macro">assert_eq!</span>(
            <span class="string">&quot;http://0.0.0.0:8000/?--dev&amp;seattle/maps/montlake.bin&quot;</span>,
            <span class="ident">change_url_free_param</span>(
                <span class="string">&quot;http://0.0.0.0:8000/?--dev&quot;</span>.<span class="ident">to_string</span>(),
                <span class="string">&quot;seattle/maps/montlake.bin&quot;</span>
            )
        );
        <span class="macro">assert_eq!</span>(
            <span class="string">&quot;http://0.0.0.0:8000/?--dev&amp;seattle/maps/qa.bin&quot;</span>,
            <span class="ident">change_url_free_param</span>(
                <span class="string">&quot;http://0.0.0.0:8000/?--dev&amp;seattle/maps/montlake.bin&quot;</span>.<span class="ident">to_string</span>(),
                <span class="string">&quot;seattle/maps/qa.bin&quot;</span>
            )
        );
        <span class="macro">assert_eq!</span>(
            <span class="string">&quot;http://0.0.0.0:8000?seattle/maps/montlake.bin&quot;</span>,
            <span class="ident">change_url_free_param</span>(
                <span class="string">&quot;http://0.0.0.0:8000&quot;</span>.<span class="ident">to_string</span>(),
                <span class="string">&quot;seattle/maps/montlake.bin&quot;</span>
            )
        );
    }

    <span class="attribute">#[<span class="ident">test</span>]</span>
    <span class="kw">fn</span> <span class="ident">test_change_url_param</span>() {
        <span class="kw">use</span> <span class="kw">super</span><span class="ident">::change_url_param</span>;

        <span class="macro">assert_eq!</span>(
            <span class="string">&quot;http://0.0.0.0:8000/?--dev&amp;seattle/maps/montlake.bin&amp;--cam=16.6/53.78449/-1.70701&quot;</span>,
            <span class="ident">change_url_param</span>(
                <span class="string">&quot;http://0.0.0.0:8000/?--dev&amp;seattle/maps/montlake.bin&quot;</span>.<span class="ident">to_string</span>(),
                <span class="string">&quot;--cam&quot;</span>,
                <span class="string">&quot;16.6/53.78449/-1.70701&quot;</span>
            )
        );
        <span class="macro">assert_eq!</span>(
            <span class="string">&quot;http://0.0.0.0:8000?--cam=16.6/53.78449/-1.70701&quot;</span>,
            <span class="ident">change_url_param</span>(
                <span class="string">&quot;http://0.0.0.0:8000&quot;</span>.<span class="ident">to_string</span>(),
                <span class="string">&quot;--cam&quot;</span>,
                <span class="string">&quot;16.6/53.78449/-1.70701&quot;</span>
            )
        );
    }
}
</pre></div>
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