142 lines
3.2 KiB
TypeScript
142 lines
3.2 KiB
TypeScript
declare type LatLonZoom = {
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lat: number;
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lon: number;
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zoom: number;
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};
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function replaceInTemplate(template: string, data: Record<string, any>) {
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const pattern = /\${\s*(\w+?)\s*}/g;
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return template.replace(pattern, (_, token) => data[token] || '');
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}
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// Throws on decode error.
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export async function onGe0Decode(template: string, url: string): Promise<Response> {
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const { pathname, search, hash } = new URL(url);
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// Filter empty pathname elements.
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const params = pathname.split('/').filter(Boolean);
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const encodedLatLonZoom = params[0];
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let name = params.length > 1 ? params[1] : undefined;
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const llz = decodeLatLonZoom(encodedLatLonZoom);
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let title = 'Organic Maps';
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if (name) {
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name = decodeURIComponent(name.replace(/\+|_/g, ' '));
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name = name.replace("'", '’'); // To embed in popup.
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title = name + ' | ' + title;
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} else {
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name = 'Shared via <a href="https://organicmaps.app">Organic Maps</a>';
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}
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template = replaceInTemplate(template, {
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...llz,
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title,
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name,
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path: pathname + search + hash, // Starts with a slash
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});
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return new Response(template, { headers: { 'content-type': 'text/html' } });
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}
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// Throws exceptions on errors.
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function decodeLatLonZoom(encodedLatLonZoom: string): LatLonZoom {
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const GE0_MAX_POINT_BYTES = 10;
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const GE0_MAX_COORD_BITS = GE0_MAX_POINT_BYTES * 3;
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let zoom = base64Reverse[encodedLatLonZoom.charCodeAt(0)];
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if (zoom > 63) throw new Error('Invalid zoom level: the url was not encoded properly');
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zoom = Math.round(zoom / 4 + 4);
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const latLonStr = encodedLatLonZoom.substr(1);
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const latLonBytes = latLonStr.length;
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let lat = 0;
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let lon = 0;
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for (let i = 0, shift = GE0_MAX_COORD_BITS - 3; i < latLonBytes; i++, shift -= 3) {
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const a = base64Reverse[latLonStr.charCodeAt(i)];
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const lat1 = (((a >> 5) & 1) << 2) | (((a >> 3) & 1) << 1) | ((a >> 1) & 1);
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const lon1 = (((a >> 4) & 1) << 2) | (((a >> 2) & 1) << 1) | (a & 1);
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lat |= lat1 << shift;
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lon |= lon1 << shift;
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}
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const middleOfSquare = 1 << (3 * (GE0_MAX_POINT_BYTES - latLonBytes) - 1);
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lat += middleOfSquare;
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lon += middleOfSquare;
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lat = (lat / ((1 << GE0_MAX_COORD_BITS) - 1)) * 180.0 - 90.0;
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lon = (lon / (1 << GE0_MAX_COORD_BITS)) * 360.0 - 180.0;
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lat = Math.round(lat * 1e5) / 1e5;
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lon = Math.round(lon * 1e5) / 1e5;
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if (lat <= -90.0 || lat >= 90.0 || lon <= -180.0 || lon >= 180.0)
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throw new Error('Invalid coordinates: the url was not encoded properly');
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return { lat, lon, zoom };
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}
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const base64Reverse: Record<number, number> = {
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65: 0,
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66: 1,
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67: 2,
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68: 3,
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69: 4,
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70: 5,
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71: 6,
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72: 7,
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73: 8,
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74: 9,
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75: 10,
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76: 11,
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77: 12,
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78: 13,
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80: 15,
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81: 16,
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82: 17,
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85: 20,
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90: 25,
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97: 26,
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98: 27,
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101: 30,
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102: 31,
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117: 46,
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118: 47,
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119: 48,
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120: 49,
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121: 50,
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122: 51,
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48: 52,
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49: 53,
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50: 54,
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52: 56,
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55: 59,
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56: 60,
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57: 61,
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45: 62,
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95: 63,
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};
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