/** Taking a design context out of a project, and putting one into another.
 *
 * Two shapes, because they answer different questions. `design-context.md` is
 * for a reader, human or otherwise: one document that says what was decided
 * and why, which can be handed to another tool as the rules to follow. The
 * bundle is for this toolchain: everything needed to rebuild the store
 * somewhere else, including the bytes of the files the user supplied.
 *
 * The bundle carries the schema version, not the store. A store file's era is
 * readable from its own keys, and stamping the browser's submission would mean
 * rewriting what it sent.
 */

import { readFile, mkdir, readdir, writeFile } from 'node:fs/promises';
import path from 'node:path';
import {
  paths,
  readAnswers,
  readContext,
  readJsonSoft,
  writeAnswers,
  writeContext,
  writeJsonAtomic,
  SCHEMA_VERSION,
} from './store.mjs';

const BUNDLE_KIND = 'impeccable-design-context';
const BUNDLE_SCHEMA = 1;

/* Generated cue PNGs run a few megabytes, so the per-file cap must clear
   them; MAX_BUNDLE_BYTES still bounds the whole. */
const MAX_FILE_BYTES = 8 * 1024 * 1024;
const MAX_BUNDLE_BYTES = 20 * 1024 * 1024;

const MIME = new Map([
  ['.svg', 'image/svg+xml'], ['.png', 'image/png'], ['.jpg', 'image/jpeg'],
  ['.jpeg', 'image/jpeg'], ['.webp', 'image/webp'], ['.gif', 'image/gif'],
  ['.woff2', 'font/woff2'], ['.woff', 'font/woff'], ['.ttf', 'font/ttf'], ['.otf', 'font/otf'],
]);

/* Exactly the three places an export puts bytes, and so exactly the three an
   import will write them back to. Anything else in a bundle is not ours. */
const ALLOWED_FILE = /^(assets\/[^/]+|fonts\/[^/]+|cue\.png)$/;

const SURFACE_LABELS = { persuade: 'Landing page', operate: 'Tool', read: 'Docs', experience: 'Portfolio' };
const ROLES = ['primary', 'secondary', 'tertiary', 'neutral'];
const PER_SURFACE = ['color-strategy', 'boundary-style', 'corner-style', 'depth-style', 'motion-energy'];

/* ============================================================
   Export
   ============================================================ */

async function collectFiles(cwd, { includeAssets = true } = {}) {
  const target = paths(cwd);
  const files = [];
  const skipped = [];
  let total = 0;

  const take = async (absolute, relative) => {
    let bytes;
    try {
      bytes = await readFile(absolute);
    } catch {
      return;
    }
    if (bytes.length > MAX_FILE_BYTES || total + bytes.length > MAX_BUNDLE_BYTES) {
      skipped.push({ path: relative, bytes: bytes.length, reason: 'too large for the bundle' });
      return;
    }
    total += bytes.length;
    files.push({
      path: relative,
      mime: MIME.get(path.extname(relative).toLowerCase()) || 'application/octet-stream',
      base64: bytes.toString('base64'),
    });
  };

  if (!includeAssets) return { files, skipped };

  for (const [dir, prefix] of [[target.assetsDir, 'assets'], [target.fontsDir, 'fonts']]) {
    let names = [];
    try {
      names = await readdir(dir);
    } catch {
      continue;
    }
    for (const name of names.sort()) await take(path.join(dir, name), `${prefix}/${name}`);
  }
  await take(target.cuePng, 'cue.png');
  return { files, skipped };
}

async function buildBundle(cwd, { includeAssets = true, now = new Date() } = {}) {
  const target = paths(cwd);
  const answers = await readAnswers(cwd);
  if (!answers) throw new Error('No design interview found. Run /impeccable document to create one.');

  const stored = (await readContext(cwd)) || { schemaVersion: SCHEMA_VERSION };
  const cues = await readJsonSoft(target.cuesJson);
  const source = typeof answers['palette-source'] === 'string' ? answers['palette-source'] : '';
  /* A seed or custom palette names no cue, so there is no image and no dealt
     entry to carry. The hexes in the answers are the palette of record. */
  const chosenCuePalette = source && cues?.palette?.[source] ? cues.palette[source] : null;

  const { files, skipped } = await collectFiles(cwd, { includeAssets });
  let designMd = null;
  try {
    designMd = await readFile(path.resolve(cwd, 'DESIGN.md'), 'utf8');
  } catch {
    /* Not written yet, which an import is told about rather than guessing. */
  }

  return {
    schemaVersion: BUNDLE_SCHEMA,
    kind: BUNDLE_KIND,
    exportedAt: now.toISOString(),
    product: { name: stored.context?.product?.name || '' },
    context: stored,
    answers,
    /* Whole, never trimmed: the questionnaire validates the manifest by its
       pair count and quietly falls back to its own set at any other number. */
    fonts: await readJsonSoft(target.fontsManifestJson),
    chosenCue: chosenCuePalette ? { slug: source, palette: chosenCuePalette } : null,
    designMd,
    files,
    ...(skipped.length ? { skipped } : {}),
  };
}

/* ============================================================
   The readable compilation
   ============================================================ */

const line = (label, value) => (value ? `- **${label}:** ${value}\n` : '');

function paletteTable(answers) {
  const rows = ROLES
    .map((role) => [role, String(answers[`palette-${role}`] || '')])
    .filter(([, hex]) => hex);
  if (!rows.length) return '';
  return `| Role | Value |\n| --- | --- |\n${rows.map(([role, hex]) => `| ${role} | \`${hex}\` |`).join('\n')}\n\n`;
}

function perSurfaceTable(answers, surfaces) {
  const rows = [];
  for (const key of PER_SURFACE) {
    for (const mode of surfaces) {
      const value = answers[`${key}-${mode}`];
      if (value) rows.push([key, SURFACE_LABELS[mode] || mode, String(value), answers[key] === value]);
    }
  }
  if (!rows.length) return '';
  return `| Question | Surface | Answer |\n| --- | --- | --- |\n${rows
    .map(([key, label, value, leads]) => `| ${key} | ${label}${leads ? ' (leads)' : ''} | ${value} |`)
    .join('\n')}\n\n`;
}

/** One document a reader, or another tool, can follow without this toolchain. */
function renderMarkdown(bundle) {
  const context = bundle.context?.context || {};
  const answers = bundle.answers || {};
  const name = bundle.product?.name || 'This product';
  const surfaces = [].concat(answers['surface-modes'] || []).filter(Boolean);
  const out = [];

  out.push(`# Design context: ${name}\n\n`);
  out.push('The decisions this product\'s design follows, and the reasoning behind them. ');
  out.push('Exported from Impeccable; treat it as the source of truth for visual and product direction.\n\n');

  const audience = context.audience || {};
  if (Object.keys(audience).length) {
    out.push('## Audience\n\n');
    out.push(line('Primary', audience.primary));
    out.push(line('Secondary', audience.secondary));
    out.push(line('On arrival', audience.emotion));
    out.push(line('Leaving with', audience.leaving));
    if (audience.needs?.length) out.push(`- **Needs:** ${audience.needs.join('; ')}\n`);
    if (audience.trust?.length) out.push(`- **Trust triggers:** ${audience.trust.join('; ')}\n`);
    if (audience.inclusion?.length) out.push(`- **Must not exclude:** ${audience.inclusion.join('; ')}\n`);
    out.push('\n');
  }

  const product = context.product || {};
  if (Object.keys(product).length) {
    out.push('## Product\n\n');
    out.push(line('Purpose', product.purpose));
    out.push(line('Success', product.success));
    out.push(line('Platform', product.platform));
    out.push(line('Primary conversion', product.conversion));
    if (product.positioning?.not) out.push(`- **Not this:** ${product.positioning.not}\n`);
    if (product.positioning?.this) out.push(`- **This:** ${product.positioning.this}\n`);
    if (product.clarities?.length) out.push(`- **Clear first:** ${product.clarities.join('; ')}\n`);
    out.push('\n');
  }

  const brand = context.brand || {};
  if (Object.keys(brand).length) {
    out.push('## Brand\n\n');
    if (brand.words?.length) out.push(line('Words', brand.words.join(', ')));
    out.push(line('Personality', brand.personality));
    if (brand.commitments?.length) out.push(`- **Commitments:** ${brand.commitments.join('; ')}\n`);
    if (brand.voice?.length) {
      out.push('\nVoice, as wording rather than adjectives:\n\n');
      for (const pair of brand.voice) {
        if (pair?.say && pair?.not) out.push(`- Say: ${pair.say}\n  Not: ${pair.not}\n`);
      }
    }
    out.push('\n');
  }

  const interview = context.interview || {};
  if (interview.references?.length || interview.antiReference) {
    out.push('## References\n\n');
    for (const reference of interview.references || []) {
      if (typeof reference === 'string') out.push(`- ${reference}\n`);
      else if (reference?.name) out.push(`- **${reference.name}**${reference.takeaway ? `: ${reference.takeaway}` : ''}\n`);
    }
    const anti = interview.antiReference;
    if (typeof anti === 'string') out.push(`- **Anti-reference:** ${anti}\n`);
    else if (anti?.name) out.push(`- **Anti-reference:** ${anti.name}${anti.why ? ` (${anti.why})` : ''}\n`);
    out.push('\n');
  }

  out.push('## Decisions\n\n');
  if (surfaces.length) {
    out.push(`Surfaces: ${surfaces.map((mode) => SURFACE_LABELS[mode] || mode).join(', ')}. `);
    out.push('The first of these owns any answer stated once for the whole product.\n\n');
  }
  out.push('### Palette\n\n');
  out.push(paletteTable(answers));
  if (bundle.chosenCue?.slug) out.push(`Sampled from the generated cue \`${bundle.chosenCue.slug}\`.\n\n`);

  out.push('### Typography\n\n');
  out.push(line('Heading', answers['font-heading']));
  out.push(line('Body', answers['font-body']));
  out.push(line('Type scale', answers['type-scale'] && `${answers['type-scale']} (${answers['type-scale-ratio']})`));
  out.push('\n');

  if (answers['icon-pack-name']) {
    out.push('### Icons\n\n');
    out.push(`- **Pack:** ${answers['icon-pack-name']}${answers['icon-pack-license'] ? ` (${answers['icon-pack-license']})` : ''}\n`);
    if (answers['icon-pack-url']) out.push(`- **Source:** ${answers['icon-pack-url']}\n`);
    out.push('\nEvery icon comes from this pack; do not mix sets.\n\n');
  }

  const perSurface = perSurfaceTable(answers, surfaces);
  if (perSurface) {
    out.push('### Per surface\n\n');
    out.push(perSurface);
  }
  if (answers['layout-structure']) out.push(`Composition: ${answers['layout-structure']}, one answer for the whole product.\n\n`);

  if (bundle.designMd) {
    out.push('## DESIGN.md\n\n');
    out.push('The design document this context produced, verbatim.\n\n');
    out.push('<!-- begin DESIGN.md -->\n\n');
    out.push(bundle.designMd.trim());
    out.push('\n\n<!-- end DESIGN.md -->\n');
  }

  return out.join('');
}

export async function exportDesignContext(cwd, { outDir, includeAssets = true, now } = {}) {
  const bundle = await buildBundle(cwd, { includeAssets, now });
  const destination = outDir ? path.resolve(cwd, outDir) : paths(cwd).exportsDir;
  await mkdir(destination, { recursive: true });

  const markdownPath = path.join(destination, 'design-context.md');
  const bundlePath = path.join(destination, 'design-context.bundle.json');
  await writeFile(markdownPath, renderMarkdown(bundle));
  await writeJsonAtomic(bundlePath, bundle);
  return { markdownPath, bundlePath, skipped: bundle.skipped || [] };
}

/* ============================================================
   Import
   ============================================================ */

export function validateBundle(bundle) {
  if (!bundle || typeof bundle !== 'object') throw new Error('That file is not a design context bundle');
  if (bundle.kind !== BUNDLE_KIND) throw new Error(`Expected a ${BUNDLE_KIND} bundle, found ${String(bundle.kind)}`);
  if (bundle.schemaVersion !== BUNDLE_SCHEMA) {
    throw new Error(`This bundle is schema version ${String(bundle.schemaVersion)}; this release reads ${BUNDLE_SCHEMA}. Update impeccable.`);
  }
  if (!bundle.answers || typeof bundle.answers !== 'object') throw new Error('The bundle carries no answers');
  return bundle;
}

export async function importDesignContext(cwd, bundle, { design = 'skip' } = {}) {
  validateBundle(bundle);
  const target = paths(cwd);

  await writeAnswers(bundle.answers, cwd);
  const context = bundle.context && typeof bundle.context === 'object'
    ? bundle.context
    : { schemaVersion: SCHEMA_VERSION };
  await writeContext(context, cwd);

  let written = 0;
  for (const file of Array.isArray(bundle.files) ? bundle.files : []) {
    const relative = String(file?.path || '');
    /* Containment is not enough on its own: a bundle could otherwise name a
       store file and overwrite what was just written. Only the three places an
       export puts bytes are accepted. */
    if (!ALLOWED_FILE.test(relative)) {
      process.stderr.write(`Skipped ${relative || '(unnamed)'}: not a place a design context keeps files\n`);
      continue;
    }
    const absolute = path.resolve(target.storeDir, relative);
    if (path.relative(target.storeDir, absolute).startsWith('..')) continue;
    await mkdir(path.dirname(absolute), { recursive: true });
    await writeFile(absolute, Buffer.from(String(file.base64 || ''), 'base64'));
    written += 1;
  }

  /* The questionnaire cannot run without a cue manifest: its palette screen
     loads the deck and the built-in seeds together, and neither arrives if the
     file is missing. An imported project gets a valid one either way, carrying
     the chosen cue's dealt values when the bundle brought them. */
  if (!(await readJsonSoft(target.cuesJson))) {
    await writeJsonAtomic(target.cuesJson, {
      cues: [],
      ...(bundle.chosenCue?.slug ? { palette: { [bundle.chosenCue.slug]: bundle.chosenCue.palette } } : { palette: {} }),
    });
  }
  if (bundle.fonts && !(await readJsonSoft(target.fontsManifestJson))) {
    await writeJsonAtomic(target.fontsManifestJson, bundle.fonts);
  }

  let designWritten = false;
  if (design === 'write' && typeof bundle.designMd === 'string' && bundle.designMd.trim()) {
    const designPath = path.resolve(cwd, 'DESIGN.md');
    if (!(await readFile(designPath, 'utf8').then(() => true).catch(() => false))) {
      await writeFile(designPath, bundle.designMd);
      designWritten = true;
    }
  }

  return { written, designWritten, designCarried: typeof bundle.designMd === 'string' && Boolean(bundle.designMd.trim()) };
}