import { defaultConfigurationService } from "../config/ConfigurationService";
import { ProviderError, SearchFailedError } from "../models/errors";
import { SearchResult } from "../models/SearchResult";
import { BaseProvider } from "../providers/BaseProvider";
import { ProviderRegistry } from "../providers/ProviderRegistry";
import { InternalProviderResult } from "../providers/types/InternalProviderResult";
import { SearchOptions } from "../types/search";
import { Logger } from "../utils/Logger";
import { limitSearchPayload } from "./budget/SearchPayloadLimiter";
import { CanonicalSearchResultBuilder } from "./normalization/CanonicalSearchResultBuilder";

/**
 * Central Search Engine orchestrator for Browse.
 * Manages provider registration, provider resolution, candidate building, and budget enforcement.
 */
export class SearchEngine {
  private registry: ProviderRegistry;
  private searchCounter: number = 0;

  constructor(providers?: BaseProvider[], registry?: ProviderRegistry) {
    this.registry = registry ?? new ProviderRegistry();
    if (providers) {
      for (const p of providers) {
        this.registerProvider(p);
      }
    }
  }

  public registerProvider(provider: BaseProvider): void {
    this.registry.register(provider);
  }

  public unregisterProvider(providerName: string): boolean {
    return this.registry.unregister(providerName);
  }

  public getProvider(providerName: string): BaseProvider | undefined {
    return this.registry.get(providerName);
  }

  public listProviders(): string[] {
    return this.registry.listNames();
  }

  public getProviders(): BaseProvider[] {
    return this.registry.getAll();
  }

  public async search(query: string, options: SearchOptions = {}): Promise<SearchResult[]> {
    this.searchCounter += 1;
    const reqId = options.requestId || `S-${Math.random().toString(36).substring(2, 6).toUpperCase()}`;
    const startTime = Date.now();
    const requestedProvider = options.provider?.toLowerCase().trim() || "auto";
    const configuredDefault = defaultConfigurationService.getWebDefaultProvider() || "auto";

    Logger.info("[SearchEngine]", `[${reqId}] Web search execution started for query: "${query}"`);

    const providersList = this.registry.getAll();
    if (providersList.length === 0) {
      Logger.error("[SearchEngine]", `[${reqId}] Search failed: No search providers are registered.`);
      throw new ProviderError("No search providers are registered.");
    }

    // 1. Explicit provider parameter requested
    if (requestedProvider !== "auto") {
      const resolved = this.getProvider(requestedProvider);
      if (!resolved) {
        Logger.error("[SearchEngine]", `[${reqId}] Search failed: Unknown provider '${requestedProvider}'`);
        throw new ProviderError(`Unknown or unregistered provider: '${options.provider}'`);
      }

      Logger.info(
        "[SearchEngine]",
        `[${reqId}] Provider Selection -> Requested: '${requestedProvider}' | Configured Default: '${configuredDefault}' | Mode: Explicit Provider | Selected: web.${requestedProvider}`
      );

      try {
        const results = await this.dispatchSingle(resolved, query, options, reqId);
        return results;
      } catch (err: unknown) {
        const errMsg = err instanceof Error ? err.message : String(err);
        Logger.error(
          "[SearchEngine]",
          `[${reqId}] Explicit provider 'web.${requestedProvider}' failed: ${errMsg}. Fallback disabled in Explicit Provider Mode.`
        );
        throw err;
      }
    }

    // 2. Explicit provider mode: Configured default provider from Settings
    if (configuredDefault !== "auto") {
      const resolved = this.getProvider(configuredDefault);
      if (!resolved) {
        Logger.error("[SearchEngine]", `[${reqId}] Search failed: Configured default provider '${configuredDefault}' is unknown or unregistered.`);
        throw new ProviderError(`Configured default provider '${configuredDefault}' is unknown or unregistered.`);
      }

      Logger.info(
        "[SearchEngine]",
        `[${reqId}] Provider Selection -> Requested: 'auto' | Configured Default: '${configuredDefault}' | Mode: Explicit Default Provider | Selected: web.${configuredDefault}`
      );

      try {
        const results = await this.dispatchSingle(resolved, query, options, reqId);
        return results;
      } catch (err: unknown) {
        const errMsg = err instanceof Error ? err.message : String(err);
        Logger.error(
          "[SearchEngine]",
          `[${reqId}] Configured default provider 'web.${configuredDefault}' failed: ${errMsg}. Fallback disabled in Explicit Provider Mode.`
        );
        throw err;
      }
    }

    // 3. Auto Provider Mode: Both requested and default are "auto". Iterate priority list with fallback.
    return this.executeFallback(query, options, reqId, requestedProvider, configuredDefault, startTime);
  }

  private async dispatchSingle(
    targetProvider: BaseProvider,
    query: string,
    options: SearchOptions,
    reqId: string
  ): Promise<SearchResult[]> {
    const candidates = await targetProvider.search(query, options);
    return this.processCandidates(candidates, reqId);
  }

  private processCandidates(
    candidates: InternalProviderResult[],
    reqId: string
  ): SearchResult[] {
    const maxSnippetLen = defaultConfigurationService.getSearchMaxSnippetLength();
    const maxPayloadChars = defaultConfigurationService.getSearchMaxPayloadCharacters();

    // 1. Canonical normalization
    const canonicalResults: SearchResult[] = [];
    for (const candidate of candidates) {
      const built = CanonicalSearchResultBuilder.build(candidate, maxSnippetLen);
      if (built) {
        canonicalResults.push(built);
      }
    }

    // 2. Payload limiting
    const limitResult = limitSearchPayload(canonicalResults, maxPayloadChars);

    if (!limitResult.success) {
      const errMsg = limitResult.reason;
      Logger.error("[SearchEngine]", `[${reqId}] Search failed at Payload Limiter: ${errMsg}`);
      throw new SearchFailedError(errMsg);
    }

    return limitResult.results;
  }

  private async executeFallback(
    query: string,
    options: SearchOptions,
    reqId: string,
    requestedProvider: string,
    configuredDefault: string,
    startTime: number
  ): Promise<SearchResult[]> {
    const priorityNames = defaultConfigurationService.getWebProviderPriority();
    const priorityIds = priorityNames
      .map((name) => ProviderRegistry.getSpec(name)?.id)
      .filter((id) => id !== undefined);
    Logger.info(
      "[SearchEngine]",
      `[${reqId}] Mode: Auto Provider Fallback Chain | Priority IDs: [${priorityIds.join(",")}] | Resolved Order: [${priorityNames.join(", ")}]`
    );
    const attemptedErrors: Record<string, string> = {};

    const orderedProviders: BaseProvider[] = [];
    for (const name of priorityNames) {
      const p = this.getProvider(name);
      if (p && !orderedProviders.includes(p)) {
        orderedProviders.push(p);
      }
    }

    if (orderedProviders.length === 0) {
      const noValMsg = "Auto (Priority Order) cannot run because the configured Provider Priority Order contains no valid providers. Update the Provider Priority Order or select a specific provider.";
      Logger.error("[SearchEngine]", `[${reqId}] ${noValMsg}`);
      throw new SearchFailedError(noValMsg, {});
    }

    let lastFailedProvider: string | null = null;
    for (const p of orderedProviders) {
      const strategy = lastFailedProvider ? `Fallback (after ${lastFailedProvider} failed)` : "Auto Fallback Chain";
      Logger.info(
        "[SearchEngine]",
        `[${reqId}] Provider Selection -> Requested: '${requestedProvider}' | Configured Default: '${configuredDefault}' | Strategy: ${strategy} | Selected: web.${p.providerName}`
      );

      try {
        const results = await this.dispatchSingle(p, query, options, reqId);
        const durationMs = Date.now() - startTime;
        Logger.info(
          "[SearchEngine]",
          `[${reqId}] Search completed. Provider: web.${p.providerName} | Duration: ${durationMs} ms | Canonical Results: ${results.length}`
        );
        return results;
      } catch (err: unknown) {
        const msg = err instanceof Error ? err.message : String(err);
        attemptedErrors[p.providerName] = msg;
        lastFailedProvider = `web.${p.providerName}`;
        Logger.warn(
          "[SearchEngine]",
          `[${reqId}] Provider web.${p.providerName} exhausted/failed: ${msg}. Moving to next provider in configured priority order.`
        );
      }
    }

    const attemptedNames = Object.keys(attemptedErrors).join(", ");
    const lastReason = Object.values(attemptedErrors).pop() ?? "Unknown error";
    Logger.error(
      "[SearchEngine]",
      `[${reqId}] Search failed completely across all attempted providers: [${attemptedNames}]`
    );
    throw new SearchFailedError(
      `All search providers failed. Attempted providers: [${attemptedNames}]. Last error: ${lastReason}`,
      attemptedErrors
    );
  }
}

import { defaultConfigurationService } from "../config/ConfigurationService";
import { ProviderError, SearchFailedError } from "../models/errors";
import { SearchResult } from "../models/SearchResult";
import { BaseProvider } from "../providers/BaseProvider";
import { ProviderRegistry } from "../providers/ProviderRegistry";
import { InternalProviderResult } from "../providers/types/InternalProviderResult";
import { SearchOptions } from "../types/search";
import { Logger } from "../utils/Logger";
import { limitSearchPayload } from "./budget/SearchPayloadLimiter";
import { CanonicalSearchResultBuilder } from "./normalization/CanonicalSearchResultBuilder";

/**
 * Central Search Engine orchestrator for Browse.
 * Manages provider registration, provider resolution, candidate building, and budget enforcement.
 */
export class SearchEngine {
  private registry: ProviderRegistry;
  private searchCounter: number = 0;

  constructor(providers?: BaseProvider[], registry?: ProviderRegistry) {
    this.registry = registry ?? new ProviderRegistry();
    if (providers) {
      for (const p of providers) {
        this.registerProvider(p);
      }
    }
  }

  public registerProvider(provider: BaseProvider): void {
    this.registry.register(provider);
  }

  public unregisterProvider(providerName: string): boolean {
    return this.registry.unregister(providerName);
  }

  public getProvider(providerName: string): BaseProvider | undefined {
    return this.registry.get(providerName);
  }

  public listProviders(): string[] {
    return this.registry.listNames();
  }

  public getProviders(): BaseProvider[] {
    return this.registry.getAll();
  }

  public async search(query: string, options: SearchOptions = {}): Promise<SearchResult[]> {
    this.searchCounter += 1;
    const reqId = options.requestId || `S-${Math.random().toString(36).substring(2, 6).toUpperCase()}`;
    const startTime = Date.now();
    const requestedProvider = options.provider?.toLowerCase().trim() || "auto";
    const configuredDefault = defaultConfigurationService.getWebDefaultProvider() || "auto";

    Logger.info("[SearchEngine]", `[${reqId}] Web search execution started for query: "${query}"`);

    const providersList = this.registry.getAll();
    if (providersList.length === 0) {
      Logger.error("[SearchEngine]", `[${reqId}] Search failed: No search providers are registered.`);
      throw new ProviderError("No search providers are registered.");
    }

    // 1. Explicit provider parameter requested
    if (requestedProvider !== "auto") {
      const resolved = this.getProvider(requestedProvider);
      if (!resolved) {
        Logger.error("[SearchEngine]", `[${reqId}] Search failed: Unknown provider '${requestedProvider}'`);
        throw new ProviderError(`Unknown or unregistered provider: '${options.provider}'`);
      }

      Logger.info(
        "[SearchEngine]",
        `[${reqId}] Provider Selection -> Requested: '${requestedProvider}' | Configured Default: '${configuredDefault}' | Mode: Explicit Provider | Selected: web.${requestedProvider}`
      );

      try {
        const results = await this.dispatchSingle(resolved, query, options, reqId);
        return results;
      } catch (err: unknown) {
        const errMsg = err instanceof Error ? err.message : String(err);
        Logger.error(
          "[SearchEngine]",
          `[${reqId}] Explicit provider 'web.${requestedProvider}' failed: ${errMsg}. Fallback disabled in Explicit Provider Mode.`
        );
        throw err;
      }
    }

    // 2. Explicit provider mode: Configured default provider from Settings
    if (configuredDefault !== "auto") {
      const resolved = this.getProvider(configuredDefault);
      if (!resolved) {
        Logger.error("[SearchEngine]", `[${reqId}] Search failed: Configured default provider '${configuredDefault}' is unknown or unregistered.`);
        throw new ProviderError(`Configured default provider '${configuredDefault}' is unknown or unregistered.`);
      }

      Logger.info(
        "[SearchEngine]",
        `[${reqId}] Provider Selection -> Requested: 'auto' | Configured Default: '${configuredDefault}' | Mode: Explicit Default Provider | Selected: web.${configuredDefault}`
      );

      try {
        const results = await this.dispatchSingle(resolved, query, options, reqId);
        return results;
      } catch (err: unknown) {
        const errMsg = err instanceof Error ? err.message : String(err);
        Logger.error(
          "[SearchEngine]",
          `[${reqId}] Configured default provider 'web.${configuredDefault}' failed: ${errMsg}. Fallback disabled in Explicit Provider Mode.`
        );
        throw err;
      }
    }

    // 3. Auto Provider Mode: Both requested and default are "auto". Iterate priority list with fallback.
    return this.executeFallback(query, options, reqId, requestedProvider, configuredDefault, startTime);
  }

  private async dispatchSingle(
    targetProvider: BaseProvider,
    query: string,
    options: SearchOptions,
    reqId: string
  ): Promise<SearchResult[]> {
    const candidates = await targetProvider.search(query, options);
    return this.processCandidates(candidates, reqId);
  }

  private processCandidates(
    candidates: InternalProviderResult[],
    reqId: string
  ): SearchResult[] {
    const maxSnippetLen = defaultConfigurationService.getSearchMaxSnippetLength();
    const maxPayloadChars = defaultConfigurationService.getSearchMaxPayloadCharacters();

    // 1. Canonical normalization
    const canonicalResults: SearchResult[] = [];
    for (const candidate of candidates) {
      const built = CanonicalSearchResultBuilder.build(candidate, maxSnippetLen);
      if (built) {
        canonicalResults.push(built);
      }
    }

    // 2. Payload limiting
    const limitResult = limitSearchPayload(canonicalResults, maxPayloadChars);

    if (!limitResult.success) {
      const errMsg = limitResult.reason;
      Logger.error("[SearchEngine]", `[${reqId}] Search failed at Payload Limiter: ${errMsg}`);
      throw new SearchFailedError(errMsg);
    }

    return limitResult.results;
  }

  private async executeFallback(
    query: string,
    options: SearchOptions,
    reqId: string,
    requestedProvider: string,
    configuredDefault: string,
    startTime: number
  ): Promise<SearchResult[]> {
    const priorityNames = defaultConfigurationService.getWebProviderPriority();
    const priorityIds = priorityNames
      .map((name) => ProviderRegistry.getSpec(name)?.id)
      .filter((id) => id !== undefined);
    Logger.info(
      "[SearchEngine]",
      `[${reqId}] Mode: Auto Provider Fallback Chain | Priority IDs: [${priorityIds.join(",")}] | Resolved Order: [${priorityNames.join(", ")}]`
    );
    const attemptedErrors: Record<string, string> = {};

    const orderedProviders: BaseProvider[] = [];
    for (const name of priorityNames) {
      const p = this.getProvider(name);
      if (p && !orderedProviders.includes(p)) {
        orderedProviders.push(p);
      }
    }

    if (orderedProviders.length === 0) {
      const noValMsg = "Auto (Priority Order) cannot run because the configured Provider Priority Order contains no valid providers. Update the Provider Priority Order or select a specific provider.";
      Logger.error("[SearchEngine]", `[${reqId}] ${noValMsg}`);
      throw new SearchFailedError(noValMsg, {});
    }

    let lastFailedProvider: string | null = null;
    for (const p of orderedProviders) {
      const strategy = lastFailedProvider ? `Fallback (after ${lastFailedProvider} failed)` : "Auto Fallback Chain";
      Logger.info(
        "[SearchEngine]",
        `[${reqId}] Provider Selection -> Requested: '${requestedProvider}' | Configured Default: '${configuredDefault}' | Strategy: ${strategy} | Selected: web.${p.providerName}`
      );

      try {
        const results = await this.dispatchSingle(p, query, options, reqId);
        const durationMs = Date.now() - startTime;
        Logger.info(
          "[SearchEngine]",
          `[${reqId}] Search completed. Provider: web.${p.providerName} | Duration: ${durationMs} ms | Canonical Results: ${results.length}`
        );
        return results;
      } catch (err: unknown) {
        const msg = err instanceof Error ? err.message : String(err);
        attemptedErrors[p.providerName] = msg;
        lastFailedProvider = `web.${p.providerName}`;
        Logger.warn(
          "[SearchEngine]",
          `[${reqId}] Provider web.${p.providerName} exhausted/failed: ${msg}. Moving to next provider in configured priority order.`
        );
      }
    }

    const attemptedNames = Object.keys(attemptedErrors).join(", ");
    const lastReason = Object.values(attemptedErrors).pop() ?? "Unknown error";
    Logger.error(
      "[SearchEngine]",
      `[${reqId}] Search failed completely across all attempted providers: [${attemptedNames}]`
    );
    throw new SearchFailedError(
      `All search providers failed. Attempted providers: [${attemptedNames}]. Last error: ${lastReason}`,
      attemptedErrors
    );
  }
}