import type { FastMCP } from 'fastmcp';
import { UserError } from 'fastmcp';
import { z } from 'zod';
import { drive_v3, docs_v1 } from 'googleapis';
import { getDriveClient, getDocsClient } from '../../clients.js';

export function register(server: FastMCP) {
  server.addTool({
    name: 'createDocumentFromTemplate',
    description:
      'Creates a new document by copying an existing template and optionally replacing placeholder text. Provide key-value pairs in the replacements parameter to substitute template variables.',
    parameters: z.strictObject({
      templateId: z.string().describe('ID of the template document to copy from.'),
      newTitle: z.string().min(1).describe('Title for the new document.'),
      parentFolderId: z
        .string()
        .optional()
        .describe(
          'ID of folder where document should be created. If not provided, creates in Drive root.'
        ),
      replacements: z
        .record(z.string())
        .optional()
        .describe(
          'Key-value pairs for text replacements in the template (e.g., {"{{NAME}}": "John Doe", "{{DATE}}": "2024-01-01"}).'
        ),
    }),
    execute: async (args, { log }) => {
      const drive = await getDriveClient();
      log.info(`Creating document from template ${args.templateId} with title "${args.newTitle}"`);

      try {
        // First copy the template
        const copyMetadata: drive_v3.Schema$File = {
          name: args.newTitle,
        };

        if (args.parentFolderId) {
          copyMetadata.parents = [args.parentFolderId];
        }

        const response = await drive.files.copy({
          fileId: args.templateId,
          requestBody: copyMetadata,
          fields: 'id,name,webViewLink',
          supportsAllDrives: true,
        });

        const document = response.data;
        let result = `Successfully created document "${document.name}" from template (ID: ${document.id})\nView Link: ${document.webViewLink}`;

        // Apply text replacements if provided
        if (args.replacements && Object.keys(args.replacements).length > 0) {
          try {
            const docs = await getDocsClient();
            const requests: docs_v1.Schema$Request[] = [];

            // Create replace requests for each replacement
            for (const [searchText, replaceText] of Object.entries(args.replacements)) {
              requests.push({
                replaceAllText: {
                  containsText: {
                    text: searchText,
                    matchCase: false,
                  },
                  replaceText: replaceText,
                },
              });
            }

            if (requests.length > 0) {
              await docs.documents.batchUpdate({
                documentId: document.id!,
                requestBody: { requests },
              });

              const replacementCount = Object.keys(args.replacements).length;
              result += `\n\nApplied ${replacementCount} text replacement${replacementCount !== 1 ? 's' : ''} to the document.`;
            }
          } catch (replacementError: any) {
            log.warn(
              `Document created but failed to apply replacements: ${replacementError.message}`
            );
            result += `\n\nDocument created but failed to apply text replacements. You can make changes manually.`;
          }
        }

        return result;
      } catch (error: any) {
        log.error(`Error creating document from template: ${error.message || error}`);
        if (error.code === 404)
          throw new UserError('Template document or parent folder not found. Check the IDs.');
        if (error.code === 403)
          throw new UserError(
            'Permission denied. Make sure you have read access to the template and write access to the destination folder.'
          );
        throw new UserError(
          `Failed to create document from template: ${error.message || 'Unknown error'}`
        );
      }
    },
  });
}