import {
  defaultLocale,
  products,
  routePrefix,
  type LocaleId,
  type ProductDef,
  type ProductId,
  type VersionDef,
} from './products.js';

/**
 * One content directory of the matrix: a (product, version, language) triple
 * mapped to its source directory and its route prefix.
 */
export interface Segment {
  product: ProductDef;
  version: VersionDef;
  locale: LocaleId;
  /** Source directory, relative to the repository root. */
  dir: string;
  /** Route prefix, without leading or trailing slash. */
  prefix: string;
}

export interface ScopeFilter {
  products?: ProductId[];
  versions?: string[];
  locales?: LocaleId[];
}

/**
 * Reads the build scope from the environment. Used to build a subset of the
 * matrix during development, where loading every version is wasteful.
 *
 *   GITEA_DOCS_PRODUCTS=docs,runner GITEA_DOCS_VERSIONS=1.27 pnpm dev
 */
export function scopeFromEnv(env: NodeJS.ProcessEnv = process.env): ScopeFilter {
  const list = (value: string | undefined) =>
    value
      ?.split(',')
      .map((item) => item.trim())
      .filter(Boolean);
  return {
    products: list(env.GITEA_DOCS_PRODUCTS) as ProductId[] | undefined,
    versions: list(env.GITEA_DOCS_VERSIONS),
    locales: list(env.GITEA_DOCS_LOCALES) as LocaleId[] | undefined,
  };
}

/** Expands the product matrix into the content directories to load. */
export function resolveSegments(filter: ScopeFilter = {}): Segment[] {
  const segments: Segment[] = [];
  for (const product of products) {
    if (product.externalBaseUrl) continue;
    if (filter.products && !filter.products.includes(product.id)) continue;
    for (const version of product.versions) {
      if (filter.versions && !filter.versions.includes(version.id)) continue;
      for (const locale of product.locales) {
        if (filter.locales && !filter.locales.includes(locale)) continue;
        const dir = version.sources[locale];
        if (!dir) continue;
        segments.push({
          product,
          version,
          locale,
          dir,
          prefix: routePrefix(product, version, locale),
        });
      }
    }
  }
  return segments;
}

/** Finds the segment a repository relative file path belongs to. */
export function segmentOf(segments: Segment[], file: string): Segment | undefined {
  let match: Segment | undefined;
  for (const segment of segments) {
    if (!file.startsWith(`${segment.dir}/`)) continue;
    // longest directory wins, `docs` must not swallow `docs-foo`
    if (!match || segment.dir.length > match.dir.length) match = segment;
  }
  return match;
}

/**
 * Route id of a source file, following these rules:
 * `index` files address their directory, a relative `slug` replaces the last
 * path segment and `slug: /` addresses the root of the version.
 */
export function routeSuffix(segment: Segment, file: string, slug?: string): string[] {
  const relative = file.slice(segment.dir.length + 1).replace(/\.mdx?$/, '');
  const parts = relative.split('/');
  const isIndex = parts.at(-1) === 'index';
  if (isIndex) parts.pop();

  if (slug === '/') {
    parts.length = 0;
  } else if (slug) {
    if (!isIndex) parts.pop();
    parts.push(...slug.replace(/^\/+|\/+$/g, '').split('/'));
  }

  return parts;
}

/**
 * Route id of a source file. Translations follow the route of their english
 * counterpart, a translated `slug` never moves a page.
 */
export function routeIdOf(segment: Segment, suffix: string[]): string {
  // the data store rejects empty ids, starlight maps `index` to the root
  return [segment.prefix, ...suffix].filter(Boolean).join('/') || 'index';
}

/** Path of a source file relative to its segment directory. */
export function relativeToSegment(segment: Segment, file: string): string {
  return file.slice(segment.dir.length + 1);
}

/** Key identifying the (product, version) a segment translates. */
export function groupKeyOf(segment: Segment): string {
  return `${segment.product.id}@${segment.version.id}`;
}

/**
 * Works out which (product, version, language) a route belongs to. Used for the
 * pages starlight builds outside of the loader, the api reference in
 * particular, so they get the same pickers, banner and search facets.
 */
export function metaFromRouteId(id: string):
  | { product: ProductId; version: string; locale: LocaleId; prefix: string }
  | undefined {
  const route = id === 'index' ? '' : id;
  let best: { product: ProductId; version: string; locale: LocaleId; prefix: string } | undefined;
  for (const product of products) {
    if (product.externalBaseUrl) continue;
    for (const version of product.versions) {
      for (const locale of product.locales) {
        const prefix = routePrefix(product, version, locale);
        // the api pages are generated by starlight-openapi, which slugifies the
        // base path: `api/1.26` is built as `api/126` and renamed afterwards
        const candidates = [prefix, slugifyPrefix(prefix)];
        if (prefix && !candidates.some((candidate) => route === candidate || route.startsWith(`${candidate}/`))) {
          continue;
        }
        if (best && best.prefix.length >= prefix.length) continue;
        best = { product: product.id, version: version.id, locale, prefix };
      }
    }
  }
  return best;
}

/** Same slugification github-slugger applies to a starlight-openapi base path. */
function slugifyPrefix(prefix: string): string {
  return prefix
    .split('/')
    .map((part) => part.toLowerCase().replace(/[^\w-]/g, ''))
    .join('/');
}

/** Url of a route id, mirroring the starlight slug to pathname rules. */
export function routeIdToPath(id: string): string {
  if (id === '' || id === 'index') return '/';
  const trimmed = id.endsWith('/index') ? id.slice(0, -'/index'.length) : id;
  return `/${trimmed}/`;
}

export { defaultLocale };