/**
 * Boot validation. Fatal problems stop the app from serving a menu it knows
 * is wrong; warnings are logged and the broken Page is skipped at render.
 */

import { access, readdir } from 'node:fs/promises';
import path from 'node:path';
import { ManifestError, readManifest, originalFileName, variantFileNames } from './manifest.ts';
import { StoredSet, sitePaths } from './sets.ts';

export interface Problem {
  level: 'fatal' | 'warning';
  message: string;
}

export interface ValidateOptions {
  dataDir: string;
  sections: readonly string[];
}

async function exists(target: string): Promise<boolean> {
  try {
    await access(target);
    return true;
  } catch {
    return false;
  }
}

async function listDirectoryNames(dir: string): Promise<string[]> {
  try {
    const entries = await readdir(dir, { withFileTypes: true });
    return entries.filter((entry) => entry.isDirectory()).map((entry) => entry.name).sort();
  } catch (error) {
    if ((error as NodeJS.ErrnoException).code === 'ENOENT') return [];
    throw error;
  }
}

export interface SiteContents {
  sets: StoredSet[];
  problems: Problem[];
}

/** Reads every set directory once; shared by validation and repair. */
export async function readSets(dataDir: string): Promise<SiteContents> {
  const paths = sitePaths(dataDir);
  const problems: Problem[] = [];
  const sets: StoredSet[] = [];

  for (const state of ['draft', 'published'] as const) {
    const base = state === 'draft' ? paths.drafts : paths.published;
    for (const sectionDir of await listDirectoryNames(base)) {
      for (const key of await listDirectoryNames(path.join(base, sectionDir))) {
        const dir = path.join(base, sectionDir, key);
        let manifest;
        try {
          manifest = await readManifest(dir);
        } catch (error) {
          const detail = error instanceof ManifestError ? error.message : String(error);
          problems.push({ level: 'fatal', message: `${dir}: ${detail}` });
          continue;
        }
        sets.push(new StoredSet(manifest, state, dir, state === 'published' ? key : null));
      }
    }
  }

  return { sets, problems };
}

export async function validateSite(options: ValidateOptions): Promise<Problem[]> {
  const paths = sitePaths(options.dataDir);
  const { sets, problems } = await readSets(options.dataDir);

  for (const set of sets) {
    const where = `${set.state}/${set.manifest.section}/${set.slug ?? set.manifest.id}`;
    if (!options.sections.includes(set.manifest.section)) {
      problems.push({ level: 'fatal', message: `${where}: Section is not in the Site config` });
    }
    if (set.manifest.section !== path.basename(path.dirname(set.dir))) {
      problems.push({ level: 'fatal', message: `${where}: manifest section does not match its directory` });
    }
    if (set.state === 'published' && set.manifest.publishedAt === null) {
      problems.push({ level: 'fatal', message: `${where}: published set has no publishedAt` });
    }
    if (set.state === 'draft' && set.manifest.publishedAt !== null) {
      problems.push({ level: 'fatal', message: `${where}: Draft has a publishedAt` });
    }
    if (set.manifest.pages.length === 0) {
      problems.push({
        level: set.state === 'published' ? 'fatal' : 'warning',
        message: `${where}: no Pages`,
      });
    }

    const originals = path.join(paths.originals, set.manifest.section, set.manifest.id);
    for (const [index, page] of set.manifest.pages.entries()) {
      const names = variantFileNames(page);
      const missing: string[] = [];
      if (!(await exists(path.join(set.dir, names.webp)))) missing.push('viewing webp');
      if (!(await exists(path.join(set.dir, names.jpeg)))) missing.push('viewing jpeg');
      if (!(await exists(path.join(set.dir, names.thumb)))) missing.push('thumbnail');
      if (!(await exists(path.join(originals, originalFileName(page))))) missing.push('original');
      if (missing.length > 0) {
        problems.push({
          level: set.state === 'published' ? 'fatal' : 'warning',
          message: `${where}: page ${index + 1} (${page.id}) is missing its ${missing.join(', ')}`,
        });
      }
    }
  }

  // Two published sets in one Section may not share a URL segment.
  const slugs = new Map<string, Set<string>>();
  for (const set of sets) {
    if (set.state !== 'published' || set.slug === null) continue;
    const key = set.manifest.section;
    const seen = slugs.get(key) ?? new Set<string>();
    if (seen.has(set.slug)) {
      problems.push({ level: 'fatal', message: `two published sets share the URL ${key}/${set.slug}` });
    }
    seen.add(set.slug);
    slugs.set(key, seen);
  }

  return problems;
}

export function hasFatal(problems: readonly Problem[]): boolean {
  return problems.some((problem) => problem.level === 'fatal');
}