import { BadRequestException, Injectable } from '@nestjs/common';
import { RedisService } from '@box/db/redis/redis.service';
import { InspectRedisKeyDto } from './dto/inspect-redis-key.dto';
import { RebuildCacheDto } from './dto/rebuild-cache.dto';
import {
  RedisInspectorGroupCode,
  ScanRedisKeysDto,
} from './dto/scan-redis-keys.dto';
import {
  RedisInspectorKeySummary,
  RedisInspectorRecordDetail,
  RedisInspectorRebuildResult,
  RedisInspectorRebuildSupportResult,
  RedisInspectorScanResult,
  RedisInspectorKeyRebuildResult,
} from './types/redis-inspector.types';
import {
  getRedisCacheRegistry,
  RedisCacheCode,
  RedisCacheKeyAllowList,
  RedisCacheRebuildHandler,
} from './redis-cache-registry';
import { LatestVideosCacheBuilder } from '@box/core/cache/video/latest/latest-videos-cache.builder';
import { RecommendedVideosCacheBuilder } from '@box/core/cache/video/recommended/recommended-videos-cache.builder';
import { TagCacheBuilder } from '@box/core/cache/tag/tag-cache.builder';
import { CategoryCacheBuilder } from '@box/core/cache/category/category-cache.builder';
import { ChannelCacheBuilder } from '@box/core/cache/channel/channel-cache.builder';
import { AdPoolBuilder } from '@box/core/ad/ad-pool.builder';
import { RebuildCacheByKeyDto } from './dto/rebuild-by-key.dto';
import { RebuildSupportDto } from './dto/rebuild-support.dto';

const GROUP_PATTERNS: Record<RedisInspectorGroupCode, string> = {
  [RedisInspectorGroupCode.CHANNEL]: 'box:app:channel*',
  [RedisInspectorGroupCode.CATEGORY]: 'box:app:category*',
  [RedisInspectorGroupCode.TAG]: 'box:app:tag*',
  [RedisInspectorGroupCode.VIDEO]: 'box:app:video*',
  [RedisInspectorGroupCode.ADS]: 'box:app:adpool*',
};
const MAX_JSON_PARSE_BYTES = 2 * 1024 * 1024;

@Injectable()
export class RedisInspectorService {
  private readonly maxPreviewBytes = 32 * 1024;
  private readonly cacheRegistry: RedisCacheRebuildHandler[];

  constructor(
    private readonly redisService: RedisService,
    latestVideosCacheBuilder: LatestVideosCacheBuilder,
    recommendedVideosCacheBuilder: RecommendedVideosCacheBuilder,
    tagCacheBuilder: TagCacheBuilder,
    categoryCacheBuilder: CategoryCacheBuilder,
    channelCacheBuilder: ChannelCacheBuilder,
    adPoolBuilder: AdPoolBuilder,
  ) {
    this.cacheRegistry = getRedisCacheRegistry({
      latestVideosCacheBuilder,
      recommendedVideosCacheBuilder,
      tagCacheBuilder,
      categoryCacheBuilder,
      channelCacheBuilder,
      adPoolBuilder,
    });
  }

  async scan(dto: ScanRedisKeysDto): Promise<RedisInspectorScanResult> {
    const count = this.normalizePageSize(dto.pageSize);
    const matchPattern = this.buildMatchPattern(dto);
    let cursor = this.normalizeCursor(dto.cursor);
    const keys: string[] = [];

    do {
      const [cursorNext, batch] = await this.redisService.scan(
        cursor,
        'MATCH',
        matchPattern,
        'COUNT',
        count,
      );

      if (batch?.length) {
        keys.push(...batch);
      }

      cursor = cursorNext;
    } while (cursor !== '0' && keys.length < count);

    if (!keys?.length) {
      return { cursorNext: cursor, items: [] };
    }

    const details = await this.redisService.pipelineTypeTtl(keys);
    const items: RedisInspectorKeySummary[] = details.map((detail) => ({
      key: detail.key,
      type: detail.type,
      ttlSec: detail.ttlSec,
    }));

    return {
      cursorNext: cursor,
      items,
    };
  }

  async inspect(dto: InspectRedisKeyDto): Promise<RedisInspectorRecordDetail> {
    const key = dto.key;
    const [type, ttlSec] = await Promise.all([
      this.redisService.type(key),
      this.redisService.ttl(key),
    ]);

    if (type === 'none' || ttlSec === -2) {
      return {
        key,
        type: 'none',
        ttlSec: -2,
        meta: {},
        preview: { format: 'text', data: null },
      };
    }

    const limit = this.normalizePageSize(dto.limit);
    const start = Math.max(0, dto.start ?? 0);
    const cursor = this.normalizeCursor(dto.cursor);

    switch (type) {
      case 'string':
        return this.inspectString(key, ttlSec);
      case 'list':
        return this.inspectList(key, ttlSec, limit, start);
      case 'zset':
        return this.inspectZset(key, ttlSec, limit, start);
      case 'hash':
        return this.inspectHash(key, ttlSec, limit, cursor);
      case 'set':
        return this.inspectSet(key, ttlSec, limit, cursor);
      default:
        return {
          key,
          type,
          ttlSec,
          meta: {},
          preview: {
            format: 'text',
            data: `Unsupported type: ${type}`,
          },
        };
    }
  }

  async rebuild(dto: RebuildCacheDto): Promise<RedisInspectorRebuildResult> {
    const handler = this.cacheRegistry.find(
      (entry) => entry.cacheCode === dto.cacheCode,
    );
    if (!handler) {
      throw new BadRequestException('Unknown cacheCode');
    }

    const result = await handler.rebuild();
    return {
      cacheCode: dto.cacheCode,
      status: 'OK',
      rebuiltAtSec: Math.floor(Date.now() / 1000),
      message: result.message,
      affected: result.affected,
    };
  }

  async rebuildByKey(
    dto: RebuildCacheByKeyDto,
  ): Promise<RedisInspectorKeyRebuildResult> {
    const key = dto.key?.trim() ?? '';
    const rebuiltAtSec = Math.floor(Date.now() / 1000);
    if (!key || !key.startsWith('box:app:')) {
      return {
        key,
        status: 'NOT_SUPPORTED',
        rebuiltAtSec,
        message: 'Invalid key format',
      };
    }

    const entry = RedisCacheKeyAllowList.find(({ matcher }) => matcher(key));
    if (!entry) {
      return {
        key,
        status: 'NOT_SUPPORTED',
        rebuiltAtSec,
        message: 'Key is not mapped to a rebuildable cache',
      };
    }

    const handler = this.findHandler(entry.cacheCode);
    if (!handler) {
      return {
        key,
        cacheCode: entry.cacheCode,
        status: 'NOT_SUPPORTED',
        rebuiltAtSec,
        message: `No rebuild handler registered for ${entry.description.toLowerCase()}`,
      };
    }

    const result = await handler.rebuild();
    return {
      key,
      cacheCode: entry.cacheCode,
      status: 'OK',
      rebuiltAtSec,
      message: result.message,
      affected: result.affected,
    };
  }

  async rebuildSupport(
    dto: RebuildSupportDto,
  ): Promise<RedisInspectorRebuildSupportResult> {
    const key = dto.key?.trim() ?? '';
    if (!key || !key.startsWith('box:app:')) {
      return {
        key,
        supported: false,
        reason: 'Invalid key format',
      };
    }

    const entry = RedisCacheKeyAllowList.find(({ matcher }) => matcher(key));
    if (!entry) {
      return {
        key,
        supported: false,
        reason: 'Key not in allow list',
      };
    }

    const handler = this.findHandler(entry.cacheCode);
    if (!handler) {
      return {
        key,
        cacheCode: entry.cacheCode,
        supported: false,
        reason: 'No rebuild handler registered for this cacheCode',
        description: entry.description,
      };
    }

    return {
      key,
      cacheCode: entry.cacheCode,
      supported: true,
      description: entry.description,
    };
  }

  private findHandler(cacheCode: RedisCacheCode) {
    return this.cacheRegistry.find((entry) => entry.cacheCode === cacheCode);
  }

  private async inspectString(
    key: string,
    ttlSec: number,
  ): Promise<RedisInspectorRecordDetail> {
    const byteLen = await this.redisService.strLen(key);
    const rawValue = (await this.redisService.get(key)) ?? '';
    const trimmedValue = rawValue.trim();
    const { text, truncated } = this.prepareStringPreview(rawValue);
    const meta: Record<string, any> = { byteLen };
    const preview: Record<string, any> = {
      format: 'text',
      data: text,
    };

    if (byteLen > MAX_JSON_PARSE_BYTES && trimmedValue.startsWith('[')) {
      const extracted = this.extractFirstJsonArrayElements(trimmedValue, 5);
      if (extracted && extracted.length) {
        preview.format = 'json';
        preview.data = extracted.map((item) => {
          try {
            return JSON.parse(item);
          } catch {
            return item;
          }
        });
        const totalItems = this.countTopLevelJsonArrayElements(trimmedValue);
        if (totalItems !== null) {
          meta.itemCount = totalItems;
          preview.truncated = totalItems > extracted.length;
        } else {
          preview.truncated = true;
        }
        return {
          key,
          type: 'string',
          ttlSec,
          meta,
          preview,
        };
      }
    }

    const canParseJson = byteLen <= MAX_JSON_PARSE_BYTES;
    const candidate = canParseJson ? this.tryParseJson(rawValue) : undefined;

    if (candidate !== undefined && Array.isArray(candidate)) {
      meta.itemCount = candidate.length;
      preview.format = 'json';
      preview.data = candidate.slice(0, 5);
      if (candidate.length > 5) {
        preview.truncated = true;
      }
      return {
        key,
        type: 'string',
        ttlSec,
        meta,
        preview,
      };
    }

    if (!truncated && candidate !== undefined) {
      preview.format = 'json';
      preview.data = candidate;
    }

    if (truncated) {
      preview.truncated = true;
    }

    return {
      key,
      type: 'string',
      ttlSec,
      meta,
      preview,
    };
  }

  private countTopLevelJsonArrayElements(raw: string): number | null {
    const trimmed = raw.trim();
    if (!trimmed.startsWith('[')) {
      return null;
    }
    let depth = 0;
    let inString = false;
    let escape = false;
    let seenNonWhitespace = false;
    let count = 0;
    for (let i = 1; i < trimmed.length; i++) {
      const char = trimmed[i];
      if (inString) {
        if (escape) {
          escape = false;
        } else if (char === '\\') {
          escape = true;
        } else if (char === '"') {
          inString = false;
        }
        continue;
      }

      if (char === '"') {
        inString = true;
        seenNonWhitespace = true;
        continue;
      }

      if (char === '{' || char === '[') {
        depth++;
        seenNonWhitespace = true;
        continue;
      }

      if (char === '}' || char === ']') {
        if (depth > 0) {
          depth--;
          continue;
        }
      }

      if (depth === 0 && (char === ',' || char === ']')) {
        if (seenNonWhitespace) {
          count++;
          seenNonWhitespace = false;
        }
        if (char === ']') {
          break;
        }
        continue;
      }

      if (!/\s/.test(char)) {
        seenNonWhitespace = true;
      }
    }

    return count;
  }

  private extractFirstJsonArrayElements(
    raw: string,
    maxItems: number,
  ): string[] | null {
    if (!raw || !raw.startsWith('[')) {
      return null;
    }
    const elements: string[] = [];
    let depth = 0;
    let inString = false;
    let escape = false;
    let elementStart: number | null = null;
    for (let i = 1; i < raw.length && elements.length < maxItems; i++) {
      const char = raw[i];
      if (elementStart === null) {
        if (/\s/.test(char)) {
          continue;
        }
        if (char === ']') {
          break;
        }
        elementStart = i;
      }

      if (inString) {
        if (escape) {
          escape = false;
        } else if (char === '\\') {
          escape = true;
        } else if (char === '"') {
          inString = false;
        }
        continue;
      }

      if (char === '"') {
        inString = true;
        continue;
      }

      if (char === '{' || char === '[') {
        depth++;
        continue;
      }

      if (char === '}' || char === ']') {
        if (depth > 0) {
          depth--;
          continue;
        }
      }

      if ((char === ',' || char === ']') && depth === 0) {
        const segment = raw.slice(elementStart, i).trim();
        if (segment) {
          elements.push(segment);
        }
        elementStart = null;
        if (char === ']') {
          break;
        }
      }
    }

    return elements.length ? elements : null;
  }

  private async inspectList(
    key: string,
    ttlSec: number,
    limit: number,
    start: number,
  ): Promise<RedisInspectorRecordDetail> {
    const length = await this.redisService.llen(key);
    const end = start + limit - 1;
    const values = await this.redisService.lrange(key, start, end);
    const nextStart = start + values.length;

    return {
      key,
      type: 'list',
      ttlSec,
      meta: { len: length },
      preview: { format: 'json', data: values },
      paging: {
        nextStart,
        hasMore: nextStart < length,
      },
    };
  }

  private async inspectZset(
    key: string,
    ttlSec: number,
    limit: number,
    start: number,
  ): Promise<RedisInspectorRecordDetail> {
    const card = await this.redisService.zcard(key);
    const end = start + limit - 1;
    const entries = await this.redisService.zrangeWithScores(key, start, end);
    const nextStart = start + entries.length;

    return {
      key,
      type: 'zset',
      ttlSec,
      meta: { card },
      preview: { format: 'json', data: entries },
      paging: {
        nextStart,
        hasMore: nextStart < card,
      },
    };
  }

  private async inspectHash(
    key: string,
    ttlSec: number,
    limit: number,
    cursor: string,
  ): Promise<RedisInspectorRecordDetail> {
    const length = await this.redisService.hlen(key);
    const [cursorNext, rawEntries] = await this.redisService.hscan(
      key,
      cursor,
      limit,
    );
    const entries = this.buildHashEntries(rawEntries);

    return {
      key,
      type: 'hash',
      ttlSec,
      meta: { len: length },
      preview: { format: 'json', data: entries },
      paging: {
        cursorNext,
        hasMore: cursorNext !== '0',
      },
    };
  }

  private async inspectSet(
    key: string,
    ttlSec: number,
    limit: number,
    cursor: string,
  ): Promise<RedisInspectorRecordDetail> {
    const card = await this.redisService.scard(key);
    const [cursorNext, members] = await this.redisService.sscan(
      key,
      cursor,
      limit,
    );

    return {
      key,
      type: 'set',
      ttlSec,
      meta: { card },
      preview: { format: 'json', data: members ?? [] },
      paging: {
        cursorNext,
        hasMore: cursorNext !== '0',
      },
    };
  }

  private prepareStringPreview(value: string): {
    text: string;
    truncated: boolean;
  } {
    if (!value) return { text: '', truncated: false };
    const buffer = Buffer.from(value, 'utf8');
    if (buffer.length <= this.maxPreviewBytes) {
      return { text: value, truncated: false };
    }
    const truncated = buffer.subarray(0, this.maxPreviewBytes).toString('utf8');
    return { text: truncated, truncated: true };
  }

  private tryParseJson(value: string): unknown | undefined {
    try {
      return JSON.parse(value);
    } catch {
      return undefined;
    }
  }

  private buildHashEntries(raw: string[]): Array<{
    field: string;
    value: unknown;
  }> {
    const entries: Array<{ field: string; value: unknown }> = [];
    for (let i = 0; i < raw.length; i += 2) {
      const field = raw[i];
      const value = raw[i + 1];
      if (field === undefined || value === undefined) {
        continue;
      }
      entries.push({
        field,
        value: this.parseHashValue(value),
      });
    }
    return entries;
  }

  private parseHashValue(value: string): unknown {
    if (!value) return value;
    if (Buffer.byteLength(value, 'utf8') > this.maxPreviewBytes) {
      return value;
    }
    const trimmed = value.trim();
    if (!this.looksLikeJson(trimmed)) {
      return value;
    }
    try {
      return JSON.parse(value);
    } catch {
      return value;
    }
  }

  private looksLikeJson(value: string): boolean {
    return (
      value.startsWith('{') || value.startsWith('[') || value.startsWith('"')
    );
  }

  private buildMatchPattern(dto: ScanRedisKeysDto): string {
    const basePattern = GROUP_PATTERNS[dto.groupCode];
    const keyword = dto.keyword?.trim();
    if (!keyword) {
      return basePattern;
    }

    const normalizedBase = basePattern.endsWith('*')
      ? basePattern.slice(0, -1)
      : basePattern;
    const containsWildcard = keyword.includes('*') || keyword.includes('?');
    const suffix = containsWildcard ? keyword : `*${keyword}*`;
    return `${normalizedBase}${suffix}`;
  }

  private normalizeCursor(cursor?: string): string {
    const trimmed = cursor?.trim();
    return trimmed && trimmed !== '' ? trimmed : '0';
  }

  private normalizePageSize(pageSize?: number): number {
    const fallback = 50;
    if (!pageSize) return fallback;
    return Math.min(Math.max(pageSize, 1), 200);
  }
}