import { eq, and, desc, like, sql, inArray, notInArray } from 'drizzle-orm';
import { type LibSQLDatabase } from 'drizzle-orm/libsql';
import type * as schema from '../schema/index';
import { contentItems } from '../schema/index';
import type { ContentItem, ContentType, ContentStatus, QualityInfo } from '../../types/index';
import type { ContentCounts } from '../../types/api';

// ── Types ──

/** Fields needed to create a new content item. */
export interface CreateContentItemData {
  channelId: number;
  title: string;
  platformContentId: string;
  url: string;
  contentType: ContentType;
  duration: number | null;
  thumbnailUrl?: string | null;
  status?: ContentStatus;
  publishedAt?: string | null;
  monitored?: boolean;
}

/** Fields that can be updated on an existing content item (post-download). */
export interface UpdateContentItemData {
  filePath?: string | null;
  fileSize?: number | null;
  format?: string | null;
  qualityMetadata?: QualityInfo | null;
  status?: ContentStatus;
  downloadedAt?: string | null;
}

type Db = LibSQLDatabase<typeof schema>;

// ── Repository Functions ──

/**
 * Insert a new content item with dedup on (channelId, platformContentId).
 * Returns the created row, or null if the item already exists.
 */
export async function createContentItem(
  db: Db,
  data: CreateContentItemData
): Promise<ContentItem | null> {
  // Check for existing item first — dedup by (channelId, platformContentId)
  const existing = await db
    .select({ id: contentItems.id })
    .from(contentItems)
    .where(
      and(
        eq(contentItems.channelId, data.channelId),
        eq(contentItems.platformContentId, data.platformContentId)
      )
    )
    .limit(1);

  if (existing.length > 0) {
    return null; // Already exists — skip
  }

  const result = await db
    .insert(contentItems)
    .values({
      channelId: data.channelId,
      title: data.title,
      platformContentId: data.platformContentId,
      url: data.url,
      contentType: data.contentType,
      duration: data.duration,
      thumbnailUrl: data.thumbnailUrl ?? null,
      status: data.status ?? 'monitored',
      publishedAt: data.publishedAt ?? null,
      monitored: data.monitored ?? true,
    })
    .returning();

  return mapRow(result[0]);
}

/** Get all content items for a channel, ordered by creation date (newest first). */
export async function getContentByChannelId(
  db: Db,
  channelId: number
): Promise<ContentItem[]> {
  const rows = await db
    .select()
    .from(contentItems)
    .where(eq(contentItems.channelId, channelId))
    .orderBy(desc(contentItems.createdAt));

  return rows.map(mapRow);
}

/** Optional filters for channel content queries. */
export interface ChannelContentFilters {
  search?: string;
  status?: ContentStatus;
  contentType?: ContentType;
  sortBy?: 'title' | 'publishedAt' | 'status' | 'duration' | 'fileSize' | 'downloadedAt';
  sortDirection?: 'asc' | 'desc';
}

/**
 * Get paginated content items for a channel with optional search, filter, and sort.
 * Returns items and total count for pagination.
 */
export async function getChannelContentPaginated(
  db: Db,
  channelId: number,
  filters?: ChannelContentFilters,
  page = 1,
  pageSize = 50
): Promise<PaginatedContentResult> {
  const conditions = [eq(contentItems.channelId, channelId)];

  if (filters?.search) {
    conditions.push(like(contentItems.title, `%${filters.search}%`));
  }
  if (filters?.status) {
    conditions.push(eq(contentItems.status, filters.status));
  }
  if (filters?.contentType) {
    conditions.push(eq(contentItems.contentType, filters.contentType));
  }

  const whereClause = and(...conditions);
  const offset = (page - 1) * pageSize;

  // Count total matching records
  const countResult = await db
    .select({ count: sql<number>`count(*)` })
    .from(contentItems)
    .where(whereClause);

  const total = Number(countResult[0].count);

  // Build sort order
  const sortCol = resolveSortColumn(filters?.sortBy);
  const sortDir = filters?.sortDirection === 'asc' ? sortCol : desc(sortCol);

  // Fetch paginated results
  const rows = await db
    .select()
    .from(contentItems)
    .where(whereClause)
    .orderBy(sortDir, desc(contentItems.id))
    .limit(pageSize)
    .offset(offset);

  return {
    items: rows.map(mapRow),
    total,
  };
}

/** Resolve sort column name to Drizzle column reference. */
function resolveSortColumn(sortBy?: string) {
  switch (sortBy) {
    case 'title': return contentItems.title;
    case 'publishedAt': return contentItems.publishedAt;
    case 'status': return contentItems.status;
    case 'duration': return contentItems.duration;
    case 'fileSize': return contentItems.fileSize;
    case 'downloadedAt': return contentItems.downloadedAt;
    default: return contentItems.createdAt;
  }
}

/** Check if a specific content item exists for a channel. Returns the item or null. */
export async function getContentByPlatformContentId(
  db: Db,
  channelId: number,
  platformContentId: string
): Promise<ContentItem | null> {
  const rows = await db
    .select()
    .from(contentItems)
    .where(
      and(
        eq(contentItems.channelId, channelId),
        eq(contentItems.platformContentId, platformContentId)
      )
    )
    .limit(1);

  return rows.length > 0 ? mapRow(rows[0]) : null;
}

/**
 * Get recent platformContentIds for a channel (for fast dedup checking during monitoring).
 * Returns just the IDs, not full rows, to minimize memory usage.
 */
export async function getRecentContentIds(
  db: Db,
  channelId: number,
  limit = 200
): Promise<string[]> {
  const rows = await db
    .select({ platformContentId: contentItems.platformContentId })
    .from(contentItems)
    .where(eq(contentItems.channelId, channelId))
    .orderBy(desc(contentItems.createdAt))
    .limit(limit);

  return rows.map((r) => r.platformContentId);
}

// ── Single-Item Access ──

/** Get a content item by ID. Returns null if not found. */
export async function getContentItemById(
  db: Db,
  id: number
): Promise<ContentItem | null> {
  const rows = await db
    .select()
    .from(contentItems)
    .where(eq(contentItems.id, id))
    .limit(1);

  return rows.length > 0 ? mapRow(rows[0]) : null;
}

/**
 * Update a content item with partial data. Sets updatedAt to now.
 * Returns updated item or null if not found.
 */
export async function updateContentItem(
  db: Db,
  id: number,
  data: UpdateContentItemData
): Promise<ContentItem | null> {
  const result = await db
    .update(contentItems)
    .set({
      ...data,
      updatedAt: sql`(datetime('now'))`,
    })
    .where(eq(contentItems.id, id))
    .returning();

  return result.length > 0 ? mapRow(result[0]) : null;
}

/**
 * Set the `monitored` flag on a single content item.
 * Returns updated item or null if not found.
 */
export async function setMonitored(
  db: Db,
  id: number,
  monitored: boolean
): Promise<ContentItem | null> {
  const result = await db
    .update(contentItems)
    .set({
      monitored,
      updatedAt: sql`(datetime('now'))`,
    })
    .where(eq(contentItems.id, id))
    .returning();

  return result.length > 0 ? mapRow(result[0]) : null;
}

/**
 * Set the `monitored` flag on multiple content items at once.
 * Returns the number of items actually updated.
 */
export async function bulkSetMonitored(
  db: Db,
  ids: number[],
  monitored: boolean
): Promise<number> {
  if (ids.length === 0) return 0;

  const result = await db
    .update(contentItems)
    .set({
      monitored,
      updatedAt: sql`(datetime('now'))`,
    })
    .where(inArray(contentItems.id, ids))
    .returning({ id: contentItems.id });

  return result.length;
}

/** Get content items by status, ordered by creation date (oldest first). */
export async function getContentItemsByStatus(
  db: Db,
  status: ContentStatus,
  limit?: number
): Promise<ContentItem[]> {
  let query = db
    .select()
    .from(contentItems)
    .where(eq(contentItems.status, status))
    .orderBy(contentItems.createdAt);

  if (limit !== undefined) {
    query = query.limit(limit) as typeof query;
  }

  const rows = await query;
  return rows.map(mapRow);
}

// ── Paginated Listing ──

/** Optional filters for querying content items. */
export interface ContentItemFilters {
  status?: ContentStatus;
  contentType?: ContentType;
  channelId?: number;
  search?: string;
}

/** Paginated result of content items. */
export interface PaginatedContentResult {
  items: ContentItem[];
  total: number;
}

/**
 * Get content items with optional filters and pagination.
 * Returns items ordered by id DESC (newest first) and total count for pagination.
 * Uses id DESC as tiebreaker per K001 (datetime granularity).
 */
export async function getAllContentItems(
  db: Db,
  filters?: ContentItemFilters,
  page = 1,
  pageSize = 25
): Promise<PaginatedContentResult> {
  const conditions = buildContentFilterConditions(filters);
  const offset = (page - 1) * pageSize;

  // Count total matching records
  const countResult = await db
    .select({ count: sql<number>`count(*)` })
    .from(contentItems)
    .where(conditions.length > 0 ? and(...conditions) : undefined);

  const total = Number(countResult[0].count);

  // Fetch paginated results
  const rows = await db
    .select()
    .from(contentItems)
    .where(conditions.length > 0 ? and(...conditions) : undefined)
    .orderBy(desc(contentItems.id))
    .limit(pageSize)
    .offset(offset);

  return {
    items: rows.map(mapRow),
    total,
  };
}

function buildContentFilterConditions(filters?: ContentItemFilters) {
  const conditions = [];

  if (filters?.status) {
    conditions.push(eq(contentItems.status, filters.status));
  }
  if (filters?.contentType) {
    conditions.push(eq(contentItems.contentType, filters.contentType));
  }
  if (filters?.channelId !== undefined) {
    conditions.push(eq(contentItems.channelId, filters.channelId));
  }
  if (filters?.search) {
    conditions.push(like(contentItems.title, `%${filters.search}%`));
  }

  return conditions;
}

// ── Content Counts by Channel ──

/**
 * Aggregate content counts (total, monitored, downloaded) grouped by channel ID.
 * Returns a Map so callers can merge counts into channel objects efficiently.
 */
export async function getContentCountsByChannelIds(
  db: Db,
  channelIds: number[]
): Promise<Map<number, ContentCounts>> {
  if (channelIds.length === 0) return new Map();

  const rows = await db
    .select({
      channelId: contentItems.channelId,
      total: sql<number>`count(*)`,
      monitored: sql<number>`sum(case when ${contentItems.monitored} = 1 then 1 else 0 end)`,
      downloaded: sql<number>`sum(case when ${contentItems.status} = 'downloaded' then 1 else 0 end)`,
    })
    .from(contentItems)
    .where(inArray(contentItems.channelId, channelIds))
    .groupBy(contentItems.channelId);

  const map = new Map<number, ContentCounts>();
  for (const row of rows) {
    map.set(row.channelId, {
      total: Number(row.total),
      monitored: Number(row.monitored),
      downloaded: Number(row.downloaded),
    });
  }
  return map;
}

// ── Collectible Items ──

/**
 * Get content items eligible for collection (download enqueueing).
 * Returns items where `monitored = true` AND status is NOT 'downloaded',
 * 'queued', or 'downloading'. Optionally filtered by channelId.
 */
export async function getCollectibleItems(
  db: Db,
  channelId?: number
): Promise<ContentItem[]> {
  const conditions = [
    eq(contentItems.monitored, true),
    notInArray(contentItems.status, ['downloaded', 'queued', 'downloading']),
  ];

  if (channelId !== undefined) {
    conditions.push(eq(contentItems.channelId, channelId));
  }

  const rows = await db
    .select()
    .from(contentItems)
    .where(and(...conditions))
    .orderBy(contentItems.id);

  return rows.map(mapRow);
}

// ── Row Mapping ──

function mapRow(row: typeof contentItems.$inferSelect): ContentItem {
  return {
    id: row.id,
    channelId: row.channelId,
    title: row.title,
    platformContentId: row.platformContentId,
    url: row.url,
    contentType: row.contentType as ContentType,
    duration: row.duration,
    filePath: row.filePath,
    fileSize: row.fileSize,
    format: row.format,
    qualityMetadata: row.qualityMetadata as ContentItem['qualityMetadata'],
    status: row.status as ContentStatus,
    thumbnailUrl: row.thumbnailUrl ?? null,
    publishedAt: row.publishedAt ?? null,
    downloadedAt: row.downloadedAt ?? null,
    monitored: row.monitored,
    createdAt: row.createdAt,
    updatedAt: row.updatedAt,
  };
}