/**
 * @license
 * Copyright 2025 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */

import { GroundingMetadata } from '@google/genai';
import {
  BaseDeclarativeTool,
  BaseToolInvocation,
  Kind,
  ToolInvocation,
  ToolResult,
} from './tools.js';

import { getErrorMessage } from '../utils/errors.js';
import { Config } from '../config/config.js';
import { getResponseText } from '../utils/generateContentResponseUtilities.js';

interface GroundingChunkWeb {
  uri?: string;
  title?: string;
}

interface GroundingChunkItem {
  web?: GroundingChunkWeb;
  // Other properties might exist if needed in the future
}

interface GroundingSupportSegment {
  startIndex: number;
  endIndex: number;
  text?: string; // text is optional as per the example
}

interface GroundingSupportItem {
  segment?: GroundingSupportSegment;
  groundingChunkIndices?: number[];
  confidenceScores?: number[]; // Optional as per example
}

/**
 * Parameters for the WebSearchTool.
 */
export interface WebSearchToolParams {
  /**
   * The search query.
   */

  query: string;
}

/**
 * Extends ToolResult to include sources for web search.
 */
export interface WebSearchToolResult extends ToolResult {
  sources?: GroundingMetadata extends { groundingChunks: GroundingChunkItem[] }
    ? GroundingMetadata['groundingChunks']
    : GroundingChunkItem[];
}

class WebSearchToolInvocation extends BaseToolInvocation<
  WebSearchToolParams,
  WebSearchToolResult
> {
  constructor(
    private readonly config: Config,
    params: WebSearchToolParams,
  ) {
    super(params);
  }

  override getDescription(): string {
    return `Searching the web for: "${this.params.query}"`;
  }

  async execute(signal: AbortSignal): Promise<WebSearchToolResult> {
    const geminiClient = this.config.getGeminiClient();

    try {
      const response = await geminiClient.generateContent(
        [{ role: 'user', parts: [{ text: this.params.query }] }],
        { tools: [{ googleSearch: {} }] },
        signal,
      );

      const responseText = getResponseText(response);
      const groundingMetadata = response.candidates?.[0]?.groundingMetadata;
      const sources = groundingMetadata?.groundingChunks as
        | GroundingChunkItem[]
        | undefined;
      const groundingSupports = groundingMetadata?.groundingSupports as
        | GroundingSupportItem[]
        | undefined;

      if (!responseText || !responseText.trim()) {
        return {
          llmContent: `No search results or information found for query: "${this.params.query}"`,
          returnDisplay: 'No information found.',
        };
      }

      let modifiedResponseText = responseText;
      const sourceListFormatted: string[] = [];

      if (sources && sources.length > 0) {
        sources.forEach((source: GroundingChunkItem, index: number) => {
          const title = source.web?.title || 'Untitled';
          const uri = source.web?.uri || 'No URI';
          sourceListFormatted.push(`[${index + 1}] ${title} (${uri})`);
        });

        if (groundingSupports && groundingSupports.length > 0) {
          const insertions: Array<{ index: number; marker: string }> = [];
          groundingSupports.forEach((support: GroundingSupportItem) => {
            if (support.segment && support.groundingChunkIndices) {
              const citationMarker = support.groundingChunkIndices
                .map((chunkIndex: number) => `[${chunkIndex + 1}]`)
                .join('');
              insertions.push({
                index: support.segment.endIndex,
                marker: citationMarker,
              });
            }
          });

          // Sort insertions by index in descending order to avoid shifting subsequent indices
          insertions.sort((a, b) => b.index - a.index);

          const responseChars = modifiedResponseText.split(''); // Use new variable
          insertions.forEach((insertion) => {
            responseChars.splice(insertion.index, 0, insertion.marker);
          });
          modifiedResponseText = responseChars.join(''); // Assign back to modifiedResponseText
        }

        if (sourceListFormatted.length > 0) {
          modifiedResponseText +=
            '\n\nSources:\n' + sourceListFormatted.join('\n');
        }
      }

      return {
        llmContent: `Web search results for "${this.params.query}":\n\n${modifiedResponseText}`,
        returnDisplay: `Search results for "${this.params.query}" returned.`,
        sources,
      };
    } catch (error: unknown) {
      const errorMessage = `Error during web search for query "${
        this.params.query
      }": ${getErrorMessage(error)}`;
      console.error(errorMessage, error);
      return {
        llmContent: `Error: ${errorMessage}`,
        returnDisplay: `Error performing web search.`,
      };
    }
  }
}

/**
 * A tool to perform web searches using Google Search via the Gemini API.
 */
export class WebSearchTool extends BaseDeclarativeTool<
  WebSearchToolParams,
  WebSearchToolResult
> {
  static readonly Name: string = 'google_web_search';

  constructor(private readonly config: Config) {
    super(
      WebSearchTool.Name,
      'GoogleSearch',
      'Performs a web search using Google Search (via the Gemini API) and returns the results. This tool is useful for finding information on the internet based on a query.',
      Kind.Search,
      {
        type: 'object',
        properties: {
          query: {
            type: 'string',
            description: 'The search query to find information on the web.',
          },
        },
        required: ['query'],
      },
    );
  }

  /**
   * Validates the parameters for the WebSearchTool.
   * @param params The parameters to validate
   * @returns An error message string if validation fails, null if valid
   */
  protected override validateToolParamValues(
    params: WebSearchToolParams,
  ): string | null {
    if (!params.query || params.query.trim() === '') {
      return "The 'query' parameter cannot be empty.";
    }
    return null;
  }

  protected createInvocation(
    params: WebSearchToolParams,
  ): ToolInvocation<WebSearchToolParams, WebSearchToolResult> {
    return new WebSearchToolInvocation(this.config, params);
  }
}