import { readFile } from 'node:fs/promises';
import path from 'node:path';
import type { GeneratedProject } from './fetch-gitea.ts';

export type SeafileResourceType = 'build' | 'demo' | 'document' | 'asset';

export type ProjectDownload = {
  name: string;
  description?: string;
  url?: string;
  type?: SeafileResourceType;
  platform?: string;
  size?: number;
  updated_at?: string;
  source?: 'seed' | 'seafile';
};

export type GeneratedShare = {
  name: string;
  description?: string;
  url?: string;
  type?: SeafileResourceType;
  project?: string;
  project_repo?: string;
  platform?: string;
  size?: number;
  updated_at?: string;
  time?: string;
  source: 'seed' | 'seafile';
};

export type SeafileSyncConfig = {
  baseUrl: string;
  token: string;
  requestTimeoutMs?: number;
  strict?: boolean;
};

type SeedShare = {
  name: string;
  description?: string;
  url?: string;
  time?: string;
};

type SeafileMappingFile = {
  projects?: ProjectResourceMapping[];
  shares?: ShareResourceMapping[];
};

type ProjectResourceMapping = {
  project_repo: string;
  downloads?: ResourceMapping[];
};

type ShareResourceMapping = ResourceMapping & {
  project?: string;
  project_repo?: string;
};

type ResourceMapping = {
  name: string;
  description?: string;
  url?: string;
  repo_id?: string;
  path?: string;
  type?: SeafileResourceType;
  platform?: string;
  size?: number;
  updated_at?: string;
  time?: string;
};

type SeafileFileDetailResponse = {
  name?: string;
  size?: number;
  mtime?: number | string;
  modifier_email?: string;
  type?: string;
};

export async function fetchSeafileSnapshot(input: {
  config: SeafileSyncConfig;
  projects: GeneratedProject[];
  seedShares: SeedShare[];
  syncedAt: string;
  mappingFilePath: string;
}) {
  const { config, projects, seedShares, syncedAt, mappingFilePath } = input;
  const mapping = await readMappingFile(mappingFilePath);
  const client = canUseSeafileApi(config) ? createSeafileClient(config) : null;

  const mappedProjects = await Promise.all(
    projects.map(async (project) => {
      const resourceEntry = mapping.projects?.find((item) => item.project_repo === project.gitea_repo);
      const downloads = await Promise.all(
        (resourceEntry?.downloads ?? []).map((download) =>
          resolveResource(download, {
            client,
            config,
            syncedAt,
          }),
        ),
      );

      const normalizedDownloads = downloads.filter(hasContent);
      const firstResolvedUrl = normalizedDownloads.find((item) => item.url)?.url;

      return {
        ...project,
        download_link: project.download_link || firstResolvedUrl || undefined,
        downloads: normalizedDownloads.length > 0 ? normalizedDownloads : undefined,
        source:
          normalizedDownloads.length > 0
            ? project.source === 'seed'
              ? 'gitea+seafile'
              : 'gitea+seafile'
            : project.source,
      } satisfies GeneratedProject;
    }),
  );

  const projectShares = mappedProjects.flatMap((project) =>
    (project.downloads ?? []).map((download) => ({
      name: download.name,
      description: download.description,
      url: download.url,
      type: download.type,
      project: project.name,
      project_repo: project.gitea_repo,
      platform: download.platform,
      size: download.size,
      updated_at: download.updated_at,
      time: download.updated_at,
      source: 'seafile' as const,
    })),
  );

  const extraShares = await Promise.all(
    (mapping.shares ?? []).map(async (share) => {
      const resolved = await resolveResource(share, {
        client,
        config,
        syncedAt,
      });

      return {
        name: resolved.name,
        description: resolved.description,
        url: resolved.url,
        type: resolved.type,
        project: share.project,
        project_repo: share.project_repo,
        platform: resolved.platform,
        size: resolved.size,
        updated_at: resolved.updated_at,
        time: share.time || resolved.updated_at || syncedAt,
        source: 'seafile' as const,
      } satisfies GeneratedShare;
    }),
  );

  const normalizedSeedShares = seedShares.map((share) => ({
    name: share.name,
    description: share.description,
    url: share.url,
    time: share.time || syncedAt,
    updated_at: share.time || syncedAt,
    source: 'seed' as const,
  }));

  const shares = dedupeShares([
    ...normalizedSeedShares,
    ...projectShares,
    ...extraShares.filter(hasContent),
  ]).sort((a, b) => Date.parse(b.updated_at || b.time || '') - Date.parse(a.updated_at || a.time || ''));

  return {
    projects: mappedProjects,
    shares,
  };
}

async function readMappingFile(filePath: string): Promise<SeafileMappingFile> {
  try {
    const raw = await readFile(filePath, 'utf-8');
    return JSON.parse(raw) as SeafileMappingFile;
  } catch (error) {
    if (isMissingFileError(error)) {
      return {};
    }
    throw error;
  }
}

async function resolveResource(
  resource: ResourceMapping,
  input: {
    client: ReturnType<typeof createSeafileClient> | null;
    config: SeafileSyncConfig;
    syncedAt: string;
  },
): Promise<ProjectDownload> {
  const fallback: ProjectDownload = {
    name: resource.name,
    description: resource.description,
    url: resource.url,
    type: resource.type,
    platform: resource.platform,
    size: resource.size,
    updated_at: resource.updated_at || resource.time || input.syncedAt,
    source: resource.url || resource.repo_id || resource.path ? 'seafile' : 'seed',
  };

  if (resource.url || !resource.repo_id || !resource.path || !input.client) {
    return fallback;
  }

  try {
    const [detail, downloadUrl] = await Promise.all([
      input.client.getJson<SeafileFileDetailResponse>(
        `/api/v2.1/repos/${resource.repo_id}/file/detail/`,
        { path: resource.path },
      ),
      input.client.getLink(`/api/v2.1/repos/${resource.repo_id}/file/`, {
        path: resource.path,
      }),
    ]);

    return {
      name: resource.name || detail.name || path.basename(resource.path),
      description: resource.description,
      url: downloadUrl || fallback.url,
      type: resource.type,
      platform: resource.platform,
      size: detail.size ?? resource.size,
      updated_at: resource.updated_at || toIsoFromMtime(detail.mtime) || input.syncedAt,
      source: 'seafile',
    };
  } catch (error) {
    const message = error instanceof Error ? error.message : String(error);
    const logLine = `[fetch-seafile] failed to resolve ${resource.path || resource.name}: ${message}`;

    if (input.config.strict) {
      throw new Error(logLine);
    }

    console.warn(logLine);
    return fallback;
  }
}

function createSeafileClient(config: SeafileSyncConfig) {
  const headers = new Headers({
    accept: 'application/json',
  });

  if (config.token) {
    headers.set('Authorization', `Token ${config.token}`);
  }

  return {
    async getJson<T>(pathname: string, query?: Record<string, string>): Promise<T> {
      const response = await fetchWithTimeout(config, pathname, query, headers);
      return (await response.json()) as T;
    },
    async getLink(pathname: string, query?: Record<string, string>) {
      const response = await fetchWithTimeout(config, pathname, query, headers);
      const text = (await response.text()).trim();

      if (!text) {
        return '';
      }

      try {
        const parsed = JSON.parse(text) as string | { url?: string; download_link?: string };
        if (typeof parsed === 'string') {
          return parsed;
        }
        return parsed.download_link || parsed.url || text;
      } catch {
        return text.replace(/^"|"$/g, '');
      }
    },
  };
}

async function fetchWithTimeout(
  config: SeafileSyncConfig,
  pathname: string,
  query: Record<string, string> | undefined,
  headers: Headers,
) {
  const url = new URL(pathname, `${trimTrailingSlash(config.baseUrl)}/`);
  if (query) {
    for (const [key, value] of Object.entries(query)) {
      url.searchParams.set(key, value);
    }
  }

  const controller = new AbortController();
  const timeout = setTimeout(() => controller.abort(), config.requestTimeoutMs ?? 15000);

  try {
    const response = await fetch(url, {
      method: 'GET',
      headers,
      signal: controller.signal,
    });

    if (!response.ok) {
      const body = await safeReadText(response);
      throw new Error(`HTTP ${response.status} ${response.statusText}${body ? ` - ${body}` : ''}`);
    }

    return response;
  } finally {
    clearTimeout(timeout);
  }
}

function hasContent(item: { name?: string; url?: string; description?: string }) {
  return Boolean(item.name || item.url || item.description);
}

function dedupeShares(items: GeneratedShare[]) {
  const seen = new Set<string>();
  return items.filter((item) => {
    const key = [item.project_repo, item.name, item.url, item.type, item.platform].join('|');
    if (seen.has(key)) {
      return false;
    }
    seen.add(key);
    return true;
  });
}

function toIsoFromMtime(value?: number | string) {
  if (typeof value === 'number') {
    const milliseconds = value > 1_000_000_000_000 ? value : value * 1000;
    return new Date(milliseconds).toISOString();
  }

  if (typeof value === 'string' && value.trim()) {
    const parsed = Date.parse(value);
    if (!Number.isNaN(parsed)) {
      return new Date(parsed).toISOString();
    }
  }

  return '';
}

function canUseSeafileApi(config: SeafileSyncConfig) {
  return Boolean(config.baseUrl && config.token);
}

function trimTrailingSlash(value: string) {
  return value.replace(/\/+$/, '');
}

function isMissingFileError(error: unknown) {
  return typeof error === 'object' && error !== null && 'code' in error && error.code === 'ENOENT';
}

async function safeReadText(response: Response) {
  try {
    return (await response.text()).slice(0, 300);
  } catch {
    return '';
  }
}