'use strict';

const path = require('node:path');

/**
 * Walks the Filestash share recursively, collects audio files, folds them
 * into logical groups (numbered variants, format duplicates, loop markers)
 * and caches the result in memory with a TTL.
 *
 * Effects are identified internally by their share-relative path (e.g.
 * "/Combat/Sword.mp3"). The public API also exposes stable group IDs
 * derived from category + base name. Clients may play by groupId/variantId
 * (preferred) or path (legacy). The media proxy always validates by path.
 */

// Format preference when multiple extensions exist for the same logical sound.
// Earlier = preferred. Adjust here if data suggests otherwise.
const FORMAT_PREFERENCE = ['ogg', 'mp3', 'm4a', 'wav', 'flac'];

class EffectsService {
  constructor({ client, extensions, ignoreNames, cacheTtlSeconds, maxDepth }) {
    this.client = client;
    this.extensions = new Set(extensions.map((e) => e.toLowerCase()));
    this.ignore = new Set(ignoreNames.map((n) => n.toLowerCase()));
    this.cacheTtlMs = Math.max(0, cacheTtlSeconds * 1000);
    this.maxDepth = Math.max(1, maxDepth);
    this.cache = null;
    this.groupsCache = null;
    this.groupsById = null;
    this.cacheLoadedAt = 0;
    this.inflight = null;
  }

  isAudioFile(name) {
    const lower = name.toLowerCase();
    if (this.ignore.has(lower)) return false;
    const ext = path.extname(lower);
    return this.extensions.has(ext);
  }

  contentTypeFor(name) {
    switch (path.extname(name).toLowerCase()) {
      case '.mp3': return 'audio/mpeg';
      case '.ogg': return 'audio/ogg';
      case '.flac': return 'audio/flac';
      case '.wav': return 'audio/wav';
      case '.m4a': return 'audio/mp4';
      default: return 'application/octet-stream';
    }
  }

  /**
   * Returns the cached flat effects list, refreshing if expired or forced.
   * Single-flight: concurrent callers share the same refresh promise.
   */
  async list({ force = false } = {}) {
    const fresh =
      this.cache &&
      !force &&
      Date.now() - this.cacheLoadedAt < this.cacheTtlMs;
    if (fresh) return this.cache;

    if (!this.inflight) {
      this.inflight = this._refresh().finally(() => {
        this.inflight = null;
      });
    }
    return this.inflight;
  }

  async listGroups({ force = false } = {}) {
    await this.list({ force });
    return this.groupsCache || [];
  }

  async _refresh() {
    const effects = [];
    const stack = [{ rel: '/', depth: 0 }];
    const visited = new Set();

    while (stack.length) {
      const { rel, depth } = stack.pop();
      if (visited.has(rel)) continue;
      visited.add(rel);

      let entries;
      try {
        entries = await this.client.listDir(rel);
      } catch (err) {
        if (rel === '/') throw err;
        // Skip unreadable sub-folders instead of aborting the whole scan.
        // eslint-disable-next-line no-console
        console.warn(`[effects] failed to list ${rel}: ${err.message}`);
        continue;
      }

      for (const entry of entries) {
        if (!entry.name || entry.name === '.' || entry.name === '..') continue;
        if (this.ignore.has(entry.name.toLowerCase())) continue;
        const childRel = joinRel(rel, entry.name);
        if (entry.type === 'directory') {
          if (depth + 1 < this.maxDepth) {
            stack.push({ rel: childRel + '/', depth: depth + 1 });
          }
          continue;
        }
        if (!this.isAudioFile(entry.name)) continue;

        const category = deriveCategory(childRel);
        const display = stripExt(entry.name);
        const parsed = parseDisplayName(display);
        effects.push({
          id: childRel,
          path: childRel,
          name: display,
          fileName: entry.name,
          category,
          type: path.extname(entry.name).slice(1).toLowerCase(),
          size: entry.size,
          baseName: parsed.baseName,
          variantNumber: parsed.variantNumber,
          isLoop: parsed.isLoop,
        });
      }
    }

    effects.sort((a, b) => {
      const c = a.category.localeCompare(b.category);
      if (c !== 0) return c;
      const bn = a.baseName.localeCompare(b.baseName);
      if (bn !== 0) return bn;
      const an = (a.variantNumber || 0) - (b.variantNumber || 0);
      if (an !== 0) return an;
      return a.name.localeCompare(b.name);
    });

    const { groups, groupsById } = buildGroups(effects);

    this.cache = effects;
    this.groupsCache = groups;
    this.groupsById = groupsById;
    this.cacheLoadedAt = Date.now();
    return effects;
  }

  async findByPath(relPath) {
    if (!isSafeRel(relPath)) return null;
    const list = await this.list();
    return list.find((e) => e.path === relPath) || null;
  }

  async findGroup(groupId) {
    if (typeof groupId !== 'string' || !groupId) return null;
    await this.list();
    return (this.groupsById && this.groupsById.get(groupId)) || null;
  }

  /**
   * Resolves a group + optional variantId to a concrete effect (one file path).
   * If variantId is omitted, picks one variant (rotating to avoid immediate
   * repeat on the server side as a fallback when the client doesn't specify).
   */
  async resolveGroupVariant(groupId, variantId) {
    const group = await this.findGroup(groupId);
    if (!group) return null;

    let variant = null;
    if (variantId) {
      variant = group.variants.find((v) => v.id === variantId) || null;
      if (!variant) return null;
    } else {
      if (!group.variants.length) return null;
      const idx = group._nextPick % group.variants.length;
      variant = group.variants[idx];
      group._nextPick = (group._nextPick + 1) % Math.max(1, group.variants.length);
    }

    const effect = await this.findByPath(variant.path);
    if (!effect) return null;
    return { group, variant, effect };
  }
}

function joinRel(parent, name) {
  const p = parent.endsWith('/') ? parent.slice(0, -1) : parent;
  return `${p}/${name}`;
}

function deriveCategory(relPath) {
  const parts = relPath.split('/').filter(Boolean);
  if (parts.length <= 1) return 'Uncategorized';
  return parts[parts.length - 2];
}

function stripExt(name) {
  const ext = path.extname(name);
  return ext ? name.slice(0, -ext.length) : name;
}

/**
 * Parses a display name (without extension) into { baseName, variantNumber, isLoop }.
 * Rules:
 *  - "(loop)" anywhere is stripped and sets isLoop. Case insensitive.
 *  - A trailing " <digits>" (after optional whitespace) is parsed as a variant
 *    number and stripped from the base name. "Sword Hit 2" -> base "Sword Hit", n=2.
 *  - Multiple internal spaces collapsed.
 */
function parseDisplayName(name) {
  let working = String(name || '').trim();
  let isLoop = false;
  if (/\(\s*loop\s*\)/i.test(working)) {
    isLoop = true;
    working = working.replace(/\(\s*loop\s*\)/ig, ' ').replace(/\s+/g, ' ').trim();
  }
  let variantNumber = null;
  const m = working.match(/^(.*?)[\s_-]+(\d{1,4})$/);
  if (m) {
    variantNumber = Number(m[2]);
    working = m[1].trim();
  }
  if (!working) working = name; // fallback so empties don't collapse
  return { baseName: working, variantNumber, isLoop };
}

function groupKey(category, baseName, isLoop) {
  return [
    'g',
    slug(category),
    slug(baseName),
    isLoop ? 'loop' : 'one',
  ].join('::');
}

function variantKey(number) {
  return number == null ? 'default' : `n${number}`;
}

function slug(s) {
  return String(s || '')
    .toLowerCase()
    .normalize('NFKD')
    .replace(/[^a-z0-9]+/g, '-')
    .replace(/^-+|-+$/g, '') || 'x';
}

/**
 * Picks the preferred file when several formats represent the same variant.
 */
function pickPreferred(files) {
  const sorted = [...files].sort((a, b) => {
    const ai = FORMAT_PREFERENCE.indexOf(a.type);
    const bi = FORMAT_PREFERENCE.indexOf(b.type);
    const ar = ai === -1 ? FORMAT_PREFERENCE.length : ai;
    const br = bi === -1 ? FORMAT_PREFERENCE.length : bi;
    if (ar !== br) return ar - br;
    return a.path.localeCompare(b.path);
  });
  return sorted[0];
}

function buildGroups(effects) {
  const byGroup = new Map();

  for (const e of effects) {
    const key = groupKey(e.category, e.baseName, e.isLoop);
    let group = byGroup.get(key);
    if (!group) {
      group = {
        id: key,
        name: e.baseName,
        category: e.category,
        isLoop: e.isLoop,
        _variantBuckets: new Map(),
      };
      byGroup.set(key, group);
    }
    const vKey = variantKey(e.variantNumber);
    let bucket = group._variantBuckets.get(vKey);
    if (!bucket) {
      bucket = { id: vKey, number: e.variantNumber, files: [] };
      group._variantBuckets.set(vKey, bucket);
    }
    bucket.files.push(e);
  }

  const groups = [];
  const groupsById = new Map();

  for (const group of byGroup.values()) {
    const variants = [];
    for (const bucket of group._variantBuckets.values()) {
      const preferred = pickPreferred(bucket.files);
      variants.push({
        id: bucket.id,
        number: bucket.number,
        name: preferred.name,
        path: preferred.path,
        type: preferred.type,
        formats: [...new Set(bucket.files.map((f) => f.type))],
        allPaths: bucket.files.map((f) => f.path),
      });
    }
    variants.sort((a, b) => {
      if (a.number == null && b.number == null) return a.name.localeCompare(b.name);
      if (a.number == null) return -1;
      if (b.number == null) return 1;
      return a.number - b.number;
    });

    const numberedVariants = variants.filter((v) => v.number != null);
    const hasNumberedVariants = numberedVariants.length >= 2;
    const tags = [group.category];
    if (group.isLoop) tags.push('loop');
    if (hasNumberedVariants) tags.push(`${numberedVariants.length} takes`);

    const out = {
      id: group.id,
      name: group.name,
      category: group.category,
      isLoop: group.isLoop,
      tags,
      hasNumberedVariants,
      variantCount: variants.length,
      variants,
      // legacy: flat list of every path under this group, used by clients
      // (and tests) that want to discover all underlying files.
      paths: variants.flatMap((v) => v.allPaths),
      _nextPick: 0,
    };

    delete group._variantBuckets;
    groups.push(out);
    groupsById.set(out.id, out);
  }

  groups.sort((a, b) => {
    const c = a.category.localeCompare(b.category);
    if (c !== 0) return c;
    return a.name.localeCompare(b.name);
  });

  return { groups, groupsById };
}

function isSafeRel(p) {
  if (typeof p !== 'string' || !p.length) return false;
  if (!p.startsWith('/')) return false;
  if (p.includes('..')) return false;
  if (p.includes('\0')) return false;
  return true;
}

module.exports = {
  EffectsService,
  isSafeRel,
  // exported for internal use / tests
  parseDisplayName,
  buildGroups,
  FORMAT_PREFERENCE,
};