sapper/src/core/create_routes.ts

import * as path from 'path';
import glob from 'glob';
import { locations } from '../config';
import { Route } from '../interfaces';

export default function create_routes({ files } = { files: glob.sync('**/*.*', { cwd: locations.routes(), dot: true, nodir: true }) }) {
    const routes: Route[] = files
        .filter((file: string) => !/(^|\/|\\)_/.test(file))
        .map((file: string) => {
            if (/(^|\/|\\)(_|\.(?!well-known))/.test(file)) return;

            if (/]\[/.test(file)) {
                throw new Error(`Invalid route ${file} — parameters must be separated`);
            }

            const base = file.replace(/\.[^/.]+$/, '');
            const parts = base.split('/'); // glob output is always posix-style
            if (parts[parts.length - 1] === 'index') parts.pop();

            return {
                files: [file],
                base,
                parts
            };
        })
        .filter(Boolean)
        .filter((a, index, array) => {
            const found = array.slice(index + 1).find(b => a.base === b.base);
            if (found) found.files.push(...a.files);
            return !found;
        })
        .sort((a, b) => {
            if (a.parts[0] === '4xx' || a.parts[0] === '5xx') return -1;
            if (b.parts[0] === '4xx' || b.parts[0] === '5xx') return 1;

            const max = Math.max(a.parts.length, b.parts.length);

            for (let i = 0; i < max; i += 1) {
                const a_part = a.parts[i];
                const b_part = b.parts[i];

                if (!a_part) return -1;
                if (!b_part) return 1;

                const a_sub_parts = get_sub_parts(a_part);
                const b_sub_parts = get_sub_parts(b_part);
                const max = Math.max(a_sub_parts.length, b_sub_parts.length);

                for (let i = 0; i < max; i += 1) {
                    const a_sub_part = a_sub_parts[i];
                    const b_sub_part = b_sub_parts[i];

                    if (!a_sub_part) return 1; // b is more specific, so goes first
                    if (!b_sub_part) return -1;

                    if (a_sub_part.dynamic !== b_sub_part.dynamic) {
                        return a_sub_part.dynamic ? 1 : -1;
                    }

                    if (!a_sub_part.dynamic && a_sub_part.content !== b_sub_part.content) {
                        return (
                            (b_sub_part.content.length - a_sub_part.content.length) ||
                            (a_sub_part.content < b_sub_part.content ? -1 : 1)
                        );
                    }
                    // If both parts dynamic, check for regexp patterns
                    if (a_sub_part.dynamic && b_sub_part.dynamic) {
                        const regexp_pattern = /\((.*?)\)/;
                        const a_match = regexp_pattern.exec(a_sub_part.content);
                        const b_match = regexp_pattern.exec(b_sub_part.content);

                        if (!a_match && b_match) {
                            return 1; // No regexp, so less specific than b
                        }
                        if (!b_match && a_match) {
                            return -1; 
                        }
                        if (a_match && b_match) {
                            return b_match[1].length - a_match[1].length;
                        }
                    }
                }
            }

            throw new Error(`The ${a.base} and ${b.base} routes clash`);
        })
        .map(({ files, base, parts }) => {
            const id = (
                parts.join('_').replace(/[[\]]/g, '$').replace(/^\d/, '_$&').replace(/[^a-zA-Z0-9_$]/g, '_')
             ) || '_';

            const params: string[] = [];
            const match_patterns: string[] = [];
            const param_pattern = /\[([^\(]+)(?:\((.+?)\))?\]/g;
            let match;
            while (match = param_pattern.exec(base)) {
                params.push(match[1]);
                if (typeof match[2] !== 'undefined') {
                    match_patterns.push(`(${match[2]}?)`);
                }
            }

            // TODO can we do all this with sub-parts? or does
            // nesting make that impossible?
            let pattern_string = '';
            let i = parts.length;
            let nested = true;
            while (i--) {
                const part = encodeURI(parts[i].normalize()).replace(/\?/g, '%3F').replace(/#/g, '%23').replace(/%5B/g, '[').replace(/%5D/g, ']');
                const dynamic = ~part.indexOf('[');

                if (dynamic) {
                    const matcher = part.replace(param_pattern, match_patterns[i] || `([^/]+?)`);
                    pattern_string = nested ? `(?:\\/${matcher}${pattern_string})?` : `\\/${matcher}${pattern_string}`;
                } else {
                    nested = false;
                    pattern_string = `\\/${part}${pattern_string}`;
                }
            }

            const pattern = new RegExp(`^${pattern_string}\\/?$`);

            const test = (url: string) => pattern.test(url);

            const exec = (url: string) => {
                const match = pattern.exec(url);
                if (!match) return;

                const result: Record<string, string> = {};
                params.forEach((param, i) => {
                    result[param] = match[i + 1];
                });

                return result;
            };

            return {
                id,
                handlers: files.map(file => ({
                    type: path.extname(file) === '.html' ? 'page' : 'route',
                    file
                })).sort((a, b) => {
                    if (a.type === 'page' && b.type === 'route') {
                        return 1;
                    }

                    if (a.type === 'route' && b.type === 'page') {
                        return -1;
                    }

                    return 0;
                }),
                pattern,
                test,
                exec,
                parts,
                params
            };
        });

    return routes;
}

function get_sub_parts(part: string) {
    return part.split(/\[(.+)\]/)
        .map((content, i) => {
            if (!content) return null;
            return {
                content,
                dynamic: i % 2 === 1
            };
        })
        .filter(Boolean);
}