// Vite config for the demo page.
//
// The demo needs the WAV bank, which lives outside this package at
// ../flow-state/test/songs (the same bank the strip/report tools read). This
// plugin gives the browser a clean, versionless URI surface for it:
//
//   GET /songs/catalog.json   -> { fps, defaultSeed, songs: [...] }  (node-side analysis)
//   GET /songs/<name>.wav     -> the raw WAV, decoded in-browser with the
//                                exact same decodeWav/analyse code the tools use
//
// In dev the files are streamed from disk; on `vite build` they are emitted
// into dist/songs so `vite preview` shows the same page.

import { defineConfig } from 'vite';
import { createReadStream, existsSync, readdirSync, readFileSync, statSync } from 'node:fs';
import { resolve, basename } from 'node:path';
import { fileURLToPath } from 'node:url';
import { loadSong } from './tools/load.js';

const BANK = fileURLToPath(new URL('../flow-state/test/songs', import.meta.url));
const PREPARED = fileURLToPath(new URL('./out/prepared', import.meta.url));

// Catalog: one full analysis per song (17 tracks, ~0.2 s each). Built once per
// server process; loads in the browser are cached client-side, so this is the
// only full sweep the demo ever pays for.
let catalogPromise = null;

function getCatalog() {
    if (!catalogPromise) catalogPromise = buildCatalog();
    return catalogPromise;
}

async function buildCatalog() {
    const files = readdirSync(BANK).filter((f) => f.endsWith('.wav')).sort();
    const songs = [];
    for (const f of files) {
        // Yield between songs so the server answers requests while the first
        // catalog builds; the page merely waits a beat.
        await new Promise((r) => setImmediate(r));
        try {
            const { song, analysis } = loadSong(resolve(BANK, f), { fps: 30, seed: 12345 });
            songs.push({
                file: f,
                name: basename(f, '.wav'),
                duration: analysis.duration,
                frames: analysis.frames,
                species: song.name,
                seed: song.seed,
                hue: song.palette.hue,
                sat: song.palette.sat,
                summary: {
                    bpm: analysis.summary.bpm,
                    beatStrength: analysis.summary.beatStrength,
                    centroid: analysis.summary.centroid,
                    flatness: analysis.summary.flatness,
                    dynamics: analysis.summary.dynamics,
                    onsetDensity: analysis.summary.onsetDensity,
                },
                laws: song.laws.map((l) => ({ start: l.start, kind: l.kind })),
            });
        } catch (err) {
            console.warn(`[song-bank] skipping ${f}: ${err.message}`);
        }
    }
    return { fps: 30, defaultSeed: 12345, songs };
}

/** Only a plain filename inside the bank may be served; never a traversal. */
function playableWav(file) {
    const resolved = resolve(BANK, file);
    if (basename(resolved) !== file || !resolved.startsWith(BANK)) return null;
    try {
        return statSync(resolved).isFile() ? resolved : null;
    } catch {
        return null;
    }
}

function songBankPlugin() {
    return {
        name: 'metabolism-song-bank',

        configureServer(server) {
            // Warm the catalog in the background so the first page load is fast.
            getCatalog();
            server.middlewares.use('/songs', (req, res, next) => {
                const pathname = decodeURIComponent((req.url || '').split('?')[0]);
                if (pathname === '/catalog.json' || pathname === '') {
                    getCatalog().then(
                        (catalog) => {
                            res.statusCode = 200;
                            res.setHeader('content-type', 'application/json; charset=utf-8');
                            res.setHeader('cache-control', 'no-cache');
                            res.end(JSON.stringify(catalog));
                        },
                        (err) => {
                            res.statusCode = 500;
                            res.end(`catalog failed: ${err.message}`);
                        }
                    );
                    return;
                }
                const file = playableWav(pathname.replace(/^\//, ''));
                if (!file) return next();
                res.statusCode = 200;
                res.setHeader('content-type', 'audio/wav');
                res.setHeader('cache-control', 'no-cache');
                createReadStream(file).pipe(res);
            });
            // Prepared analyses (tools/prepare.js) make viewing skip analysis.
            server.middlewares.use('/prepared', (req, res, next) => {
                const name = decodeURIComponent((req.url || '').split('?')[0]).replace(/^\//, '');
                const file = resolve(PREPARED, name);
                if (basename(file) !== name || !file.startsWith(PREPARED)) return next();
                try {
                    if (!statSync(file).isFile()) return next();
                } catch {
                    return next();
                }
                res.statusCode = 200;
                res.setHeader('content-type', 'application/json; charset=utf-8');
                res.setHeader('cache-control', 'no-cache');
                createReadStream(file).pipe(res);
            });
        },

        async generateBundle() {
            const catalog = await getCatalog();
            for (const s of catalog.songs) {
                const file = playableWav(s.file);
                if (file) this.emitFile({ type: 'asset', fileName: `songs/${s.file}`, source: readFileSync(file) });
            }
            this.emitFile({ type: 'asset', fileName: 'songs/catalog.json', source: JSON.stringify(catalog) });
            if (existsSync(PREPARED)) {
                for (const f of readdirSync(PREPARED).filter((f) => f.endsWith('.json'))) {
                    this.emitFile({ type: 'asset', fileName: `prepared/${f}`, source: readFileSync(resolve(PREPARED, f)) });
                }
            }
        },
    };
}

export default defineConfig({
    plugins: [songBankPlugin()],
    // Cross-origin isolation: browsers expose SharedArrayBuffer only when
    // both headers are present. The region pool needs it once the sim runs
    // inside a browser worker; the demo is fully same-origin, so requiring
    // corp costs nothing here.
    server: {
        headers: {
            'Cross-Origin-Opener-Policy': 'same-origin',
            'Cross-Origin-Embedder-Policy': 'require-corp',
        },
    },
    preview: {
        headers: {
            'Cross-Origin-Opener-Policy': 'same-origin',
            'Cross-Origin-Embedder-Policy': 'require-corp',
        },
    },
});