import type { Database } from 'bun:sqlite';
import { createHash } from 'node:crypto';
import { openEmailDb, upsertFromRawEml, setSyncMeta, getSyncMeta } from './store';
import { getUserByEmail, getUserIntegration, upsertUserIntegration, getServerIntegration, getDockPaths, setDockPaths } from 'officerdb';
import { updateEmailAccountStatus, getEmailAccount } from '../db/queries';
import { refreshGoogleAccessToken } from '@@/api/integrations/google-auth';

import type { SyncStep, SyncCtx } from './sync-runner';

// Thrown by the handlers for failures that a retry cannot fix (missing credentials, deleted account).
// The queue used it to skip retrying; here it is an ordinary error whose message reaches the sync state.
export class PermanentError extends Error {}

// ── Credentials ──

export type GmailCredentials = {
  email: string;
  userId: number;
  appPassword?: string;
  accessToken?: string;
  refreshToken?: string;
  expiresAt?: number;
};

export async function loadGmailCredentials(userEmail: string): Promise<GmailCredentials> {
  const dbUser = await getUserByEmail(userEmail);
  if (!dbUser) throw new PermanentError('User not found');

  const userGoogle = await getUserIntegration(dbUser.id, 'google');
  const config = userGoogle?.config as Record<string, unknown> | undefined;

  const gmailEmail = (config?.email as string) ?? userEmail;

  // Prefer OAuth tokens, fall back to app password
  if (config?.accessToken && config?.refreshToken) {
    return {
      email: gmailEmail,
      userId: dbUser.id,
      accessToken: config.accessToken as string,
      refreshToken: config.refreshToken as string,
      expiresAt: config.expiresAt as number | undefined,
      appPassword: config.imapAppPassword as string | undefined,
    };
  }

  if (!config?.imapAppPassword) {
    throw new PermanentError('Gmail App Password not configured — set it in Settings → Integrations');
  }

  return { email: gmailEmail, userId: dbUser.id, appPassword: config.imapAppPassword as string };
}

// ── Stable ID from Message-Id header ──

function messageIdToStableId(raw: string): string | null {
  const match = raw.match(/^Message-Id:\s*<?([^>\s]+)>?/im);
  if (!match?.[1]) return null;
  return createHash('sha1').update(match[1]).digest('hex').slice(0, 16);
}

// ── Gmail API label → our label mapping ──

const GMAIL_API_LABEL_MAP: Record<string, string> = {
  INBOX: 'inbox',
  SENT: 'sent',
  DRAFT: 'draft',
  STARRED: 'starred',
  IMPORTANT: 'important',
  TRASH: 'trash',
  SPAM: 'spam',
  CATEGORY_PROMOTIONS: 'promotions',
  CATEGORY_SOCIAL: 'social',
  CATEGORY_UPDATES: 'updates',
  CATEGORY_FORUMS: 'forums',
};

const SKIP_LABELS = new Set(['TRASH', 'SPAM', 'DRAFT']);

function gmailApiLabelsToLabels(labelIds: string[]): string[] {
  const labels: string[] = [];
  for (const id of labelIds) {
    const mapped = GMAIL_API_LABEL_MAP[id];
    if (mapped) {
      labels.push(mapped);
    } else if (!id.startsWith('CATEGORY_') && id !== 'UNREAD' && id !== 'IMPORTANT') {
      // Custom label — use as-is (Gmail API returns label IDs, not names, for custom labels)
      labels.push(id.toLowerCase());
    }
  }
  return labels;
}

function shouldSkipMessage(labelIds: string[]): boolean {
  return labelIds.some((id) => SKIP_LABELS.has(id));
}

// ── Gmail API helpers ──

const GMAIL_API = 'https://gmail.googleapis.com/gmail/v1/users/me';

export type GmailApiResult = { saved: number; skipped: number; errors: number };

async function gmailApiFetch(accessToken: string, path: string, params?: Record<string, string>): Promise<Response> {
  const url = new URL(`${GMAIL_API}${path}`);
  if (params) {
    for (const [k, v] of Object.entries(params)) url.searchParams.set(k, v);
  }
  const res = await fetch(url, { headers: { Authorization: `Bearer ${accessToken}` } });
  return res;
}

async function getGmailProfile(accessToken: string): Promise<{ historyId: string }> {
  const res = await gmailApiFetch(accessToken, '/profile');
  if (!res.ok) throw new Error(`Gmail profile request failed: ${res.status} ${await res.text()}`);
  const data = (await res.json()) as { historyId: string };
  return data;
}

type HistoryMessage = { id: string; threadId: string };
type HistoryEntry = { messagesAdded?: Array<{ message: HistoryMessage }> };
type HistoryResponse = { history?: HistoryEntry[]; historyId: string; nextPageToken?: string };

async function getHistoryChanges(
  accessToken: string,
  startHistoryId: string,
): Promise<{ messageIds: string[]; historyId: string }> {
  const messageIds = new Set<string>();
  let pageToken: string | undefined;
  let latestHistoryId = startHistoryId;

  while (true) {
    const params: Record<string, string> = {
      startHistoryId,
      historyTypes: 'messageAdded',
      maxResults: '500',
    };
    if (pageToken) params.pageToken = pageToken;

    const res = await gmailApiFetch(accessToken, '/history', params);

    if (res.status === 404 || res.status === 410) {
      // historyId too old or invalid — caller should fall back to date-based listing
      throw new HistoryExpiredError();
    }

    if (!res.ok) throw new Error(`Gmail history request failed: ${res.status} ${await res.text()}`);

    const data = (await res.json()) as HistoryResponse;
    latestHistoryId = data.historyId;

    if (data.history) {
      for (const entry of data.history) {
        if (entry.messagesAdded) {
          for (const added of entry.messagesAdded) {
            messageIds.add(added.message.id);
          }
        }
      }
    }

    if (!data.nextPageToken) break;
    pageToken = data.nextPageToken;
  }

  return { messageIds: [...messageIds], historyId: latestHistoryId };
}

class HistoryExpiredError extends Error {
  constructor() {
    super('Gmail historyId expired');
  }
}

type MessageListResponse = { messages?: Array<{ id: string }>; nextPageToken?: string };

async function listMessagesSince(accessToken: string, sinceDate: string): Promise<string[]> {
  const messageIds: string[] = [];
  let pageToken: string | undefined;

  while (true) {
    const params: Record<string, string> = {
      q: `after:${sinceDate}`,
      maxResults: '500',
    };
    if (pageToken) params.pageToken = pageToken;

    const res = await gmailApiFetch(accessToken, '/messages', params);
    if (!res.ok) throw new Error(`Gmail messages.list failed: ${res.status} ${await res.text()}`);

    const data = (await res.json()) as MessageListResponse;
    if (data.messages) {
      for (const msg of data.messages) messageIds.push(msg.id);
    }

    if (!data.nextPageToken) break;
    pageToken = data.nextPageToken;
  }

  return messageIds;
}

type GmailMessage = { id: string; labelIds: string[]; raw: string; historyId: string };

async function fetchRawMessage(accessToken: string, messageId: string): Promise<GmailMessage | null> {
  const res = await gmailApiFetch(accessToken, `/messages/${messageId}`, { format: 'raw' });
  if (res.status === 404) return null;
  if (!res.ok) throw new Error(`Gmail messages.get failed: ${res.status} ${await res.text()}`);
  return (await res.json()) as GmailMessage;
}

// ── Gmail API sync (for resyncs) ──

export type GmailApiSyncParams = {
  creds: GmailCredentials;
  db: Database;
  onProgress?: (saved: number, total: number) => void;
};

export async function gmailApiSync({ creds, db, onProgress }: GmailApiSyncParams): Promise<GmailApiResult> {
  if (!creds.accessToken) throw new PermanentError('OAuth access token required for Gmail API sync');

  let saved = 0;
  let skipped = 0;
  let errors = 0;

  // Load existing IDs for dedup
  const existingIds = new Set<string>();
  const rows = db.query('SELECT id FROM emails').all() as Array<{ id: string }>;
  for (const row of rows) existingIds.add(row.id);

  const storedHistoryId = getSyncMeta(db, 'gmail_history_id');

  let messageIds: string[];
  let newHistoryId: string;

  if (storedHistoryId) {
    // Try history-based sync first
    try {
      const result = await getHistoryChanges(creds.accessToken, storedHistoryId);
      messageIds = result.messageIds;
      newHistoryId = result.historyId;
      console.log(`[gmail-sync] History returned ${messageIds.length} new message(s)`);
    } catch (err) {
      if (err instanceof HistoryExpiredError) {
        // historyId too old — fall back to date-based listing
        const lastSyncDate = getSyncMeta(db, 'last_sync_date');
        const sinceDate = lastSyncDate ?? new Date(Date.now() - 7 * 24 * 60 * 60 * 1000).toISOString().split('T')[0]!;
        console.log(`[gmail-sync] History expired, falling back to messages since ${sinceDate}`);
        messageIds = await listMessagesSince(creds.accessToken, sinceDate);
        const profile = await getGmailProfile(creds.accessToken);
        newHistoryId = profile.historyId;
        console.log(`[gmail-sync] Date query returned ${messageIds.length} message(s)`);
      } else {
        throw err;
      }
    }
  } else {
    // No historyId stored — use date-based listing
    const lastSyncDate = getSyncMeta(db, 'last_sync_date');
    const sinceDate = lastSyncDate ?? new Date(Date.now() - 7 * 24 * 60 * 60 * 1000).toISOString().split('T')[0]!;
    console.log(`[gmail-sync] No historyId, listing messages since ${sinceDate}`);
    messageIds = await listMessagesSince(creds.accessToken, sinceDate);
    const profile = await getGmailProfile(creds.accessToken);
    newHistoryId = profile.historyId;
    console.log(`[gmail-sync] Date query returned ${messageIds.length} message(s)`);
  }

  // Fetch and store each new message
  for (let i = 0; i < messageIds.length; i++) {
    const gmailId = messageIds[i]!;

    try {
      const msg = await fetchRawMessage(creds.accessToken, gmailId);
      if (!msg) {
        skipped++;
        continue;
      }

      if (shouldSkipMessage(msg.labelIds ?? [])) {
        skipped++;
        continue;
      }

      // Gmail API returns base64url-encoded raw RFC822
      const rawBytes = Buffer.from(msg.raw, 'base64url');
      const raw = rawBytes.toString('utf-8');

      const id = messageIdToStableId(raw);
      if (!id) {
        errors++;
        continue;
      }

      if (existingIds.has(id)) {
        skipped++;
        continue;
      }

      const labels = gmailApiLabelsToLabels(msg.labelIds ?? []);

      upsertFromRawEml({ db, id, raw, integration: 'gmail', emailAccount: creds.email, labels });
      existingIds.add(id);
      saved++;

      if ((saved + skipped) % 50 === 0) {
        onProgress?.(saved, messageIds.length);
      }
    } catch (err) {
      console.log(`[gmail-sync] Error fetching message ${gmailId}: ${err instanceof Error ? err.message : err}`);
      errors++;
    }
  }

  // Persist new historyId
  setSyncMeta(db, 'gmail_history_id', newHistoryId);

  return { saved, skipped, errors };
}

// ── IMAP sync (for first sync) ──

// Folder → label mapping for IMAP
const GMAIL_PREFIX_RE = /^\[(?:Gmail|Google Mail)\]\//;

function normalizeGmailFolder(folder: string): string {
  return folder.replace(GMAIL_PREFIX_RE, '');
}

const SUFFIX_LABEL_MAP: Record<string, string> = {
  'Sent Mail': 'sent',
  Drafts: 'draft',
  Starred: 'starred',
  Important: 'important',
  'All Mail': 'archive',
  Trash: 'trash',
  Bin: 'trash',
  Spam: 'spam',
};

function folderToLabel(folder: string): string | null {
  const suffix = normalizeGmailFolder(folder);
  if (suffix !== folder) {
    if (SUFFIX_LABEL_MAP[suffix]) return SUFFIX_LABEL_MAP[suffix]!;
    return suffix.toLowerCase();
  }
  if (folder === 'INBOX') return 'inbox';
  return folder.toLowerCase();
}

const IMAP_LABEL_MAP: Record<string, string> = {
  '\\Inbox': 'inbox',
  '\\Sent': 'sent',
  '\\Drafts': 'draft',
  '\\Starred': 'starred',
  '\\Important': 'important',
  '\\All': 'archive',
  '\\Trash': 'trash',
  '\\Junk': 'spam',
};

function imapLabelsToLabels(gmailLabels: Set<string>): string[] {
  const labels: string[] = [];
  for (const gl of gmailLabels) {
    const mapped = IMAP_LABEL_MAP[gl];
    if (mapped) {
      labels.push(mapped);
    } else if (!gl.startsWith('\\')) {
      labels.push(gl.toLowerCase());
    }
  }
  if (labels.length > 1 && labels.includes('archive')) {
    return labels.filter((l) => l !== 'archive');
  }
  return labels;
}

const SKIP_SPECIAL_USE = new Set(['\\Trash', '\\Junk', '\\All']);

function shouldSkipFolder(folder: { specialUse?: string; path: string; flags: Set<string> }): boolean {
  if (folder.flags.has('\\Noselect') || folder.flags.has('\\NonExistent')) return true;
  if (folder.specialUse && SKIP_SPECIAL_USE.has(folder.specialUse)) return true;
  const norm = normalizeGmailFolder(folder.path);
  return norm === 'All Mail' || norm === 'Trash' || norm === 'Spam' || norm === 'Bin';
}

type ImapSyncParams = {
  creds: GmailCredentials;
  db: Database;
  onProgress?: (fetched: number, folder: string) => void;
};

type SyncResult = { saved: number; skipped: number; errors: number };

async function imapFullSync({ creds, db, onProgress }: ImapSyncParams): Promise<SyncResult> {
  const { ImapFlow } = await import('imapflow');

  const auth: { user: string; pass?: string; accessToken?: string } = { user: creds.email };
  if (creds.appPassword) {
    auth.pass = creds.appPassword;
  } else if (creds.accessToken) {
    auth.accessToken = creds.accessToken;
  } else {
    throw new PermanentError('No authentication method available for IMAP');
  }

  const client = new ImapFlow({
    host: 'imap.gmail.com',
    port: 993,
    secure: true,
    auth,
    logger: false,
  });

  let saved = 0;
  let skipped = 0;
  let errors = 0;

  try {
    await client.connect();
    console.log('[gmail-sync] IMAP connected for full sync');

    const folders = await client.list({ statusQuery: { uidNext: true, uidValidity: true } });

    const existingIds = new Set<string>();
    const rows = db.query('SELECT id FROM emails').all() as Array<{ id: string }>;
    for (const row of rows) existingIds.add(row.id);

    const foldersToSync: typeof folders = [];
    for (const folder of folders) {
      if (shouldSkipFolder(folder)) continue;

      const folderPath = folder.path;
      const uidValidityKey = `imap_uidvalidity:${folderPath}`;
      const lastUidKey = `imap_lastuid:${folderPath}`;
      const storedUidValidity = getSyncMeta(db, uidValidityKey);
      const storedLastUid = getSyncMeta(db, lastUidKey);

      const uidValidity = folder.status?.uidValidity ? String(folder.status.uidValidity) : null;
      const uidNext = folder.status?.uidNext ?? 0;
      const lastUid =
        storedUidValidity && uidValidity === storedUidValidity && storedLastUid ? parseInt(storedLastUid, 10) : 0;

      if (uidValidity) setSyncMeta(db, uidValidityKey, uidValidity);
      if (lastUid > 0 && uidNext <= lastUid + 1) continue;

      foldersToSync.push(folder);
    }

    console.log(`[gmail-sync] ${foldersToSync.length} folder(s) to sync`);

    for (const folder of foldersToSync) {
      const folderPath = folder.path;
      const uidValidityKey = `imap_uidvalidity:${folderPath}`;
      const lastUidKey = `imap_lastuid:${folderPath}`;
      const storedUidValidity = getSyncMeta(db, uidValidityKey);
      const storedLastUid = getSyncMeta(db, lastUidKey);

      let lock;
      try {
        lock = await client.getMailboxLock(folderPath);
      } catch (err) {
        console.log(`[gmail-sync] Skipping folder ${folderPath}: ${err instanceof Error ? err.message : err}`);
        continue;
      }

      try {
        const mailbox = client.mailbox;
        if (!mailbox) continue;

        const uidValidity = String(mailbox.uidValidity);
        let lastUid = 0;
        if (storedUidValidity === uidValidity && storedLastUid) {
          lastUid = parseInt(storedLastUid, 10);
        }

        const range = lastUid > 0 ? `${lastUid + 1}:*` : '1:*';
        let maxUid = lastUid;
        let folderFetched = 0;

        try {
          for await (const msg of client.fetch(range, { source: true, labels: true, uid: true }, { uid: true })) {
            if (msg.uid <= lastUid) continue;

            maxUid = Math.max(maxUid, msg.uid);
            folderFetched++;

            if (!msg.source) {
              errors++;
              continue;
            }

            const raw = msg.source.toString('utf-8');
            const id = messageIdToStableId(raw);
            if (!id) {
              errors++;
              continue;
            }

            if (existingIds.has(id)) {
              skipped++;
              continue;
            }

            const folderLabel = folderToLabel(folderPath);
            const gmailLabels = msg.labels ? imapLabelsToLabels(msg.labels) : [];
            const labels = folderLabel ? [...new Set([folderLabel, ...gmailLabels])] : gmailLabels;

            try {
              upsertFromRawEml({ db, id, raw, integration: 'gmail', emailAccount: creds.email, labels });
              existingIds.add(id);
              saved++;
            } catch {
              errors++;
            }
          }
        } catch (fetchErr) {
          const msg = fetchErr instanceof Error ? fetchErr.message : String(fetchErr);
          if (!msg.includes('Nothing to fetch')) {
            console.log(`[gmail-sync] Fetch error in ${folderPath}: ${msg}`);
            errors++;
          }
        }

        if (maxUid > lastUid) {
          setSyncMeta(db, lastUidKey, String(maxUid));
        }
        setSyncMeta(db, uidValidityKey, uidValidity);

        if (folderFetched > 0) {
          console.log(`[gmail-sync] ${folderPath}: fetched ${folderFetched}, saved ${saved}, skipped ${skipped}`);
          onProgress?.(saved + skipped, folderPath);
        }
      } finally {
        lock.release();
      }
    }
  } finally {
    await client.logout().catch(() => {});
  }

  return { saved, skipped, errors };
}

// ── Handler ──

const gmailSyncHandler = {
  type: 'gmail-sync',
  retry: { delayMs: 15 * 60 * 1000, maxRetries: 10 },
  steps: [
    {
      name: 'Verify credentials',
      run: async (ctx: SyncCtx) => {
        const creds = await loadGmailCredentials(ctx.job.userId);
        const emailAccountId = (ctx.meta as Record<string, unknown>).emailAccountId as number | undefined;
        const syncAccount = emailAccountId ? await getEmailAccount(emailAccountId) : undefined;

        // Determine sync mode — check SQLite first, fall back to PostgreSQL syncMeta
        const db = openEmailDb(ctx.job.userId, syncAccount?.email ?? ctx.job.userId);
        let lastSyncAt: string | null = null;
        try {
          lastSyncAt = getSyncMeta(db, 'last_sync_at');
          if (!lastSyncAt && emailAccountId) {
            const pgAccount = await getEmailAccount(emailAccountId);
            const pgMeta = pgAccount?.syncMeta as Record<string, string> | null;
            if (pgMeta?.last_sync_at) {
              lastSyncAt = pgMeta.last_sync_at;
              // Backfill SQLite so future checks don't need PostgreSQL
              setSyncMeta(db, 'last_sync_at', lastSyncAt);
              if (pgMeta.last_sync_date) setSyncMeta(db, 'last_sync_date', pgMeta.last_sync_date);
            }
          }
          ctx.meta.isFirstSync = !lastSyncAt;
        } finally {
          db.close();
        }

        if (emailAccountId) {
          await updateEmailAccountStatus(emailAccountId, 'syncing');
          ctx.meta.emailAccountId = emailAccountId;
        }

        // For API resyncs, refresh OAuth token if expired
        if (!ctx.meta.isFirstSync && creds.accessToken && creds.refreshToken) {
          const tokenExpired = !creds.expiresAt || creds.expiresAt < Date.now() + 60_000;
          if (tokenExpired) {
            console.log('[gmail-sync] Refreshing OAuth token');
            try {
              const refreshed = await refreshGoogleAccessToken(creds.refreshToken);
              creds.accessToken = refreshed.accessToken;
              creds.expiresAt = refreshed.expiresAt;

              const userGoogle = await getUserIntegration(creds.userId, 'google');
              const existingConfig = (userGoogle?.config as Record<string, unknown>) ?? {};
              const serverGoogle = await getServerIntegration('google');
              await upsertUserIntegration({
                userId: creds.userId,
                provider: 'google',
                serverIntegrationId: serverGoogle?.id,
                config: { ...existingConfig, accessToken: refreshed.accessToken, expiresAt: refreshed.expiresAt },
              });
            } catch (err) {
              throw new PermanentError(`OAuth refresh failed — reconnect Google in Settings: ${err}`);
            }
          }
        }

        if (!ctx.meta.isFirstSync && !creds.accessToken) {
          throw new PermanentError('OAuth not configured — connect Google in Settings → Integrations for resyncs');
        }

        ctx.meta.creds = creds;
        console.log(
          `[gmail-sync] ${ctx.meta.isFirstSync ? 'First sync (IMAP)' : 'Resync (Gmail API)'} — ${creds.accessToken ? 'OAuth' : 'App Password'}`,
        );
      },
    },
    {
      name: 'Sync emails',
      run: async (ctx: SyncCtx) => {
        const creds = ctx.meta.creds as GmailCredentials;

        const emailAccountId = (ctx.meta as Record<string, unknown>).emailAccountId as number | undefined;
        const syncAccount = emailAccountId ? await getEmailAccount(emailAccountId) : undefined;
        const db = openEmailDb(ctx.job.userId, syncAccount?.email ?? ctx.job.userId);
        try {
          let result: SyncResult;

          if (ctx.meta.isFirstSync) {
            // First sync: IMAP with app password
            await ctx.updateProgress({ current: 0, total: 0, label: 'Connecting to Gmail (IMAP)...' });

            result = await imapFullSync({
              creds,
              db,
              onProgress: (fetched, folder) => {
                ctx.updateProgress({ current: fetched, total: 0, label: `Syncing ${folder}...` });
              },
            });

            // Seed historyId for future API syncs
            if (creds.accessToken) {
              try {
                const profile = await getGmailProfile(creds.accessToken);
                setSyncMeta(db, 'gmail_history_id', profile.historyId);
                console.log(`[gmail-sync] Seeded historyId: ${profile.historyId}`);
              } catch (err) {
                console.log(`[gmail-sync] Could not seed historyId: ${err}`);
              }
            }
          } else {
            // Resync: Gmail API with OAuth
            await ctx.updateProgress({ current: 0, total: 0, label: 'Checking for new emails...' });

            result = await gmailApiSync({
              creds,
              db,
              onProgress: (saved, total) => {
                ctx.updateProgress({ current: saved, total, label: `Fetching new emails (${saved}/${total})...` });
              },
            });
          }

          console.log(`[gmail-sync] Done: saved ${result.saved}, skipped ${result.skipped}, errors ${result.errors}`);

          setSyncMeta(db, 'last_sync_date', new Date().toISOString().split('T')[0]!);
          setSyncMeta(db, 'last_sync_at', new Date().toISOString());

          ctx.meta.syncResult = result;
          await ctx.updateProgress({ current: 1, total: 1, label: `Done — ${result.saved} new emails` });
        } finally {
          db.close();
        }
      },
    },
    {
      name: 'Finalize',
      run: async (ctx: SyncCtx) => {
        const result = ctx.meta.syncResult as SyncResult | undefined;
        const emailAccountId = ctx.meta.emailAccountId as number | undefined;

        if (emailAccountId) {
          await updateEmailAccountStatus(emailAccountId, 'synced');
        }

        if (result && result.saved > 0) {
          try {
            const dbUser = await getUserByEmail(ctx.job.userId);
            if (dbUser) {
              const paths = await getDockPaths(dbUser.id);
              if (!paths) {
                const defaults = ['/', '/files', '/automation', '/dashboards', '/chat'];
                await setDockPaths(dbUser.id, [...defaults, '/email']);
              } else if (!paths.includes('/email')) {
                await setDockPaths(dbUser.id, [...paths, '/email']);
              }
            }
          } catch {
            // Non-fatal
          }
        }
      },
    },
  ],
};

/** The handler's steps, for the sidecar's own runner. */
export const gmailSyncSteps: SyncStep[] = gmailSyncHandler.steps as SyncStep[];