import { Injectable } from '@nestjs/common';
import { InjectDataSource } from '@nestjs/typeorm';
import { DataSource } from 'typeorm';
import { Notification, NotificationType, TargetType, TagLogic } from '../../domain/entities/notification.entity';

export interface CreateNotificationDto {
  title: string;
  content: string;
  type: NotificationType;
  priority: string;
  targetType: TargetType;
  // Targeting payloads
  tenantIds?: string[];          // SPECIFIC_TENANTS
  userIds?: string[];            // SPECIFIC_USERS
  targetTagIds?: string[];       // BY_TENANT_TAG
  targetTagLogic?: TagLogic;     // BY_TENANT_TAG: ANY | ALL
  targetPlans?: string[];        // BY_PLAN: ['free','pro','enterprise']
  targetStatuses?: string[];     // BY_TENANT_STATUS: ['active','suspended']
  targetSegment?: string;        // BY_SEGMENT: segment key
  channelKey?: string | null;    // Phase 2 opt-out channel
  imageUrl?: string | null;
  linkUrl?: string | null;
  requiresForceRead: boolean;
  isEnabled: boolean;
  publishedAt?: Date | null;
  expiresAt?: Date | null;
  createdBy?: string;
}

export interface NotificationWithReadStatus extends Notification {
  isRead: boolean;
}

@Injectable()
export class NotificationRepository {
  constructor(@InjectDataSource() private readonly ds: DataSource) {}

  // ── Write Operations ──────────────────────────────────────────────────────

  async create(dto: CreateNotificationDto): Promise<Notification> {
    const result = await this.ds.query(
      `INSERT INTO public.notifications
         (title, content, type, priority, target_type,
          target_tag_ids, target_tag_logic, target_plans, target_statuses,
          target_segment, channel_key,
          image_url, link_url, requires_force_read, is_enabled,
          published_at, expires_at, created_by)
       VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12,$13,$14,$15,$16,$17,$18)
       RETURNING *`,
      [
        dto.title, dto.content, dto.type, dto.priority, dto.targetType,
        dto.targetTagIds?.length ? dto.targetTagIds : null,
        dto.targetTagLogic ?? 'ANY',
        dto.targetPlans?.length ? dto.targetPlans : null,
        dto.targetStatuses?.length ? dto.targetStatuses : null,
        dto.targetSegment ?? null,
        dto.channelKey ?? null,
        dto.imageUrl ?? null, dto.linkUrl ?? null,
        dto.requiresForceRead, dto.isEnabled,
        dto.publishedAt ?? null, dto.expiresAt ?? null, dto.createdBy ?? null,
      ],
    );
    const row = result[0];

    if (dto.targetType === 'SPECIFIC_TENANTS' && dto.tenantIds?.length) {
      for (const tid of dto.tenantIds) {
        await this.ds.query(
          `INSERT INTO public.notification_tenant_targets (notification_id, tenant_id)
           VALUES ($1, $2) ON CONFLICT DO NOTHING`,
          [row.id, tid],
        );
      }
    }

    if (dto.targetType === 'SPECIFIC_USERS' && dto.userIds?.length) {
      for (const uid of dto.userIds) {
        await this.ds.query(
          `INSERT INTO public.notification_user_targets (notification_id, user_id)
           VALUES ($1, $2) ON CONFLICT DO NOTHING`,
          [row.id, uid],
        );
      }
    }

    return this.mapRow(row);
  }

  async update(id: string, dto: Partial<CreateNotificationDto>): Promise<Notification | null> {
    const fields: string[] = [];
    const values: any[] = [];
    let idx = 1;

    const add = (col: string, val: any) => { fields.push(`${col} = $${idx++}`); values.push(val); };

    if (dto.title !== undefined) add('title', dto.title);
    if (dto.content !== undefined) add('content', dto.content);
    if (dto.type !== undefined) add('type', dto.type);
    if (dto.priority !== undefined) add('priority', dto.priority);
    if (dto.targetType !== undefined) add('target_type', dto.targetType);
    if (dto.targetTagIds !== undefined) add('target_tag_ids', dto.targetTagIds?.length ? dto.targetTagIds : null);
    if (dto.targetTagLogic !== undefined) add('target_tag_logic', dto.targetTagLogic);
    if (dto.targetPlans !== undefined) add('target_plans', dto.targetPlans?.length ? dto.targetPlans : null);
    if (dto.targetStatuses !== undefined) add('target_statuses', dto.targetStatuses?.length ? dto.targetStatuses : null);
    if (dto.targetSegment !== undefined) add('target_segment', dto.targetSegment);
    if (dto.channelKey !== undefined) add('channel_key', dto.channelKey);
    if (dto.imageUrl !== undefined) add('image_url', dto.imageUrl);
    if (dto.linkUrl !== undefined) add('link_url', dto.linkUrl);
    if (dto.requiresForceRead !== undefined) add('requires_force_read', dto.requiresForceRead);
    if (dto.isEnabled !== undefined) add('is_enabled', dto.isEnabled);
    if (dto.publishedAt !== undefined) add('published_at', dto.publishedAt);
    if (dto.expiresAt !== undefined) add('expires_at', dto.expiresAt);
    fields.push(`updated_at = NOW()`);

    if (fields.length === 1) return this.findById(id);

    values.push(id);
    const result = await this.ds.query(
      `UPDATE public.notifications SET ${fields.join(', ')} WHERE id = $${idx} RETURNING *`,
      values,
    );
    if (!result.length) return null;

    // Re-sync SPECIFIC_TENANTS targets
    if (dto.targetType !== undefined || dto.tenantIds !== undefined) {
      await this.ds.query(`DELETE FROM public.notification_tenant_targets WHERE notification_id = $1`, [id]);
      const newType = dto.targetType ?? (await this.findById(id))?.targetType;
      if (newType === 'SPECIFIC_TENANTS' && dto.tenantIds?.length) {
        for (const tid of dto.tenantIds) {
          await this.ds.query(
            `INSERT INTO public.notification_tenant_targets (notification_id, tenant_id) VALUES ($1, $2) ON CONFLICT DO NOTHING`,
            [id, tid],
          );
        }
      }
    }

    // Re-sync SPECIFIC_USERS targets
    if (dto.targetType !== undefined || dto.userIds !== undefined) {
      await this.ds.query(`DELETE FROM public.notification_user_targets WHERE notification_id = $1`, [id]);
      const newType = dto.targetType ?? (await this.findById(id))?.targetType;
      if (newType === 'SPECIFIC_USERS' && dto.userIds?.length) {
        for (const uid of dto.userIds) {
          await this.ds.query(
            `INSERT INTO public.notification_user_targets (notification_id, user_id) VALUES ($1, $2) ON CONFLICT DO NOTHING`,
            [id, uid],
          );
        }
      }
    }

    return this.mapRow(result[0]);
  }

  async delete(id: string): Promise<void> {
    await this.ds.query(`DELETE FROM public.notification_tenant_targets WHERE notification_id = $1`, [id]);
    await this.ds.query(`DELETE FROM public.notification_user_targets WHERE notification_id = $1`, [id]);
    await this.ds.query(`DELETE FROM public.notification_reads WHERE notification_id = $1`, [id]);
    await this.ds.query(`DELETE FROM public.notifications WHERE id = $1`, [id]);
  }

  async findById(id: string): Promise<Notification | null> {
    const rows = await this.ds.query(`SELECT * FROM public.notifications WHERE id = $1`, [id]);
    return rows.length ? this.mapRow(rows[0]) : null;
  }

  async findAllAdmin(params: {
    type?: string;
    targetType?: string;
    limit: number;
    offset: number;
  }): Promise<{ items: (Notification & { tenantIds: string[]; userIds: string[] })[]; total: number }> {
    const conds: string[] = [];
    const baseArgs: any[] = [];
    let p = 1;
    if (params.type) { conds.push(`type = $${p++}`); baseArgs.push(params.type); }
    if (params.targetType) { conds.push(`target_type = $${p++}`); baseArgs.push(params.targetType); }
    const where = conds.length ? `WHERE ${conds.join(' AND ')}` : '';

    const [rows, count] = await Promise.all([
      this.ds.query(
        `SELECT * FROM public.notifications ${where} ORDER BY created_at DESC LIMIT $${p} OFFSET $${p + 1}`,
        [...baseArgs, params.limit, params.offset],
      ),
      this.ds.query(`SELECT COUNT(*)::int AS total FROM public.notifications ${where}`, baseArgs),
    ]);

    const items = await Promise.all(
      rows.map(async (r: any) => {
        const [tenants, users] = await Promise.all([
          this.ds.query(`SELECT tenant_id FROM public.notification_tenant_targets WHERE notification_id = $1`, [r.id]),
          this.ds.query(`SELECT user_id FROM public.notification_user_targets WHERE notification_id = $1`, [r.id]),
        ]);
        return {
          ...this.mapRow(r),
          tenantIds: tenants.map((t: any) => t.tenant_id),
          userIds: users.map((u: any) => u.user_id),
        };
      }),
    );

    return { items, total: count[0]?.total ?? 0 };
  }

  // ── User-facing delivery ──────────────────────────────────────────────────

  async findForUser(params: {
    tenantId: string;
    userId: string;
    tenantPlan?: string;
    tenantStatus?: string;
    limit: number;
    offset: number;
  }): Promise<{ items: NotificationWithReadStatus[]; total: number }> {
    const { tenantId, userId, tenantPlan, tenantStatus, limit, offset } = params;
    const targeting = this._targetingSQL();
    const channelFilter = this._channelFilterSQL();

    const baseWhere = `
      n.is_enabled = true
      AND (n.published_at IS NULL OR n.published_at <= NOW())
      AND (n.expires_at IS NULL OR n.expires_at > NOW())
      AND ${targeting}
      AND ${channelFilter}`;

    const [rows, count] = await Promise.all([
      this.ds.query(
        `SELECT n.*, CASE WHEN nr.id IS NOT NULL THEN true ELSE false END AS is_read
         FROM public.notifications n
         LEFT JOIN public.notification_reads nr ON nr.notification_id = n.id AND nr.user_id = $2
         WHERE ${baseWhere}
         ORDER BY n.requires_force_read DESC, n.priority DESC,
                  COALESCE(n.published_at, n.created_at) DESC
         LIMIT $5 OFFSET $6`,
        [tenantId, userId, tenantPlan ?? null, tenantStatus ?? null, limit, offset],
      ),
      this.ds.query(
        `SELECT COUNT(*)::int AS total FROM public.notifications n WHERE ${baseWhere}`,
        [tenantId, userId, tenantPlan ?? null, tenantStatus ?? null],
      ),
    ]);

    return {
      items: rows.map((r: any) => ({ ...this.mapRow(r), isRead: r.is_read })),
      total: count[0]?.total ?? 0,
    };
  }

  async getUnreadCount(tenantId: string, userId: string, tenantPlan?: string, tenantStatus?: string): Promise<number> {
    const targeting = this._targetingSQL();
    const result = await this.ds.query(
      `SELECT COUNT(*)::int AS cnt
       FROM public.notifications n
       WHERE n.is_enabled = true
         AND (n.published_at IS NULL OR n.published_at <= NOW())
         AND (n.expires_at IS NULL OR n.expires_at > NOW())
         AND ${targeting}
         AND NOT EXISTS (
           SELECT 1 FROM public.notification_reads nr
           WHERE nr.notification_id = n.id AND nr.user_id = $2
         )`,
      [tenantId, userId, tenantPlan ?? null, tenantStatus ?? null],
    );
    return result[0]?.cnt ?? 0;
  }

  async markRead(notificationId: string, userId: string, tenantId: string): Promise<void> {
    await this.ds.query(
      `INSERT INTO public.notification_reads (notification_id, user_id, tenant_id)
       VALUES ($1, $2, $3) ON CONFLICT (notification_id, user_id) DO NOTHING`,
      [notificationId, userId, tenantId],
    );
  }

  async markAllRead(tenantId: string, userId: string): Promise<void> {
    await this.ds.query(
      `INSERT INTO public.notification_reads (notification_id, user_id, tenant_id)
       SELECT n.id, $2, $1
       FROM public.notifications n
       WHERE n.is_enabled = true
         AND (n.published_at IS NULL OR n.published_at <= NOW())
         AND (n.expires_at IS NULL OR n.expires_at > NOW())
         AND (n.target_type = 'ALL'
           OR (n.target_type = 'SPECIFIC_TENANTS' AND EXISTS (
             SELECT 1 FROM public.notification_tenant_targets t
             WHERE t.notification_id = n.id AND t.tenant_id = $1)))
       ON CONFLICT (notification_id, user_id) DO NOTHING`,
      [tenantId, userId],
    );
  }

  // ── Analytics ─────────────────────────────────────────────────────────────

  async getDeliveryStats(notificationId: string): Promise<{ readCount: number }> {
    const result = await this.ds.query(
      `SELECT COUNT(*)::int AS cnt FROM public.notification_reads WHERE notification_id = $1`,
      [notificationId],
    );
    return { readCount: result[0]?.cnt ?? 0 };
  }

  // ── SQL helpers ───────────────────────────────────────────────────────────

  private _targetingSQL(): string {
    return `(
      n.target_type = 'ALL'

      OR (n.target_type = 'SPECIFIC_TENANTS' AND EXISTS (
        SELECT 1 FROM public.notification_tenant_targets t
        WHERE t.notification_id = n.id AND t.tenant_id = $1))

      OR (n.target_type = 'SPECIFIC_USERS' AND EXISTS (
        SELECT 1 FROM public.notification_user_targets u
        WHERE u.notification_id = n.id AND u.user_id = $2))

      OR (n.target_type = 'BY_TENANT_TAG' AND n.target_tag_ids IS NOT NULL AND (
        CASE WHEN n.target_tag_logic = 'ALL' THEN
          (SELECT COUNT(*) FROM public.tenant_tag_assignments ta
           WHERE ta.tenant_id = $1 AND ta.tag_id = ANY(n.target_tag_ids))
          = array_length(n.target_tag_ids, 1)
        ELSE
          EXISTS (SELECT 1 FROM public.tenant_tag_assignments ta
                  WHERE ta.tenant_id = $1 AND ta.tag_id = ANY(n.target_tag_ids))
        END))

      OR (n.target_type = 'BY_PLAN' AND $3::text IS NOT NULL
          AND n.target_plans IS NOT NULL AND $3 = ANY(n.target_plans))

      OR (n.target_type = 'BY_TENANT_STATUS' AND $4::text IS NOT NULL
          AND n.target_statuses IS NOT NULL AND $4 = ANY(n.target_statuses))

      OR (n.target_type = 'BY_SEGMENT' AND EXISTS (
        SELECT 1 FROM public.notification_segment_members sm
        WHERE sm.segment_key = n.target_segment AND sm.tenant_id = $1))
    )`;
  }

  private _channelFilterSQL(): string {
    return `(
      n.channel_key IS NULL
      OR n.channel_key IN (
        SELECT c.channel_key FROM public.notification_channels c
        WHERE c.is_mandatory = true)
      OR NOT EXISTS (
        SELECT 1 FROM public.user_notification_preferences pref
        WHERE pref.user_id = $2
          AND pref.channel_key = n.channel_key
          AND pref.enabled = false)
    )`;
  }

  mapRow(r: any): Notification {
    return {
      id: r.id, title: r.title, content: r.content,
      type: r.type, priority: r.priority, targetType: r.target_type,
      targetTagIds: r.target_tag_ids, targetTagLogic: r.target_tag_logic ?? 'ANY',
      targetPlans: r.target_plans, targetStatuses: r.target_statuses,
      targetSegment: r.target_segment, channelKey: r.channel_key,
      imageUrl: r.image_url, linkUrl: r.link_url,
      requiresForceRead: r.requires_force_read, isEnabled: r.is_enabled,
      publishedAt: r.published_at, expiresAt: r.expires_at,
      createdBy: r.created_by, createdAt: r.created_at, updatedAt: r.updated_at,
    } as Notification;
  }
}