/**
 * Git PR Context Gatherer
 *
 * Extracts PR context from git branches for validation
 */

import { execSync } from 'child_process';
import { PRContext, FileChange } from './types';
import { JiraClient } from '@nihal1983/context-gatherer';

export interface GitPRContextOptions {
  repoPath: string;
  branch: string;
  baseBranch?: string;
  jiraClient?: JiraClient;
}

export class GitPRContextGatherer {
  private repoPath: string;
  private branch: string;
  private baseBranch: string;
  private jiraClient?: JiraClient;

  constructor(options: GitPRContextOptions) {
    this.repoPath = options.repoPath;
    this.branch = options.branch;
    this.baseBranch = options.baseBranch || 'master';
    this.jiraClient = options.jiraClient;
  }

  /**
   * Gather full PR context from git branch
   */
  async gatherContext(): Promise<PRContext> {
    // Get commit message from branch
    const commitMessage = this.getCommitMessage();
    const { title, description } = this.parseCommitMessage(commitMessage);

    // Extract ticket ID from commit message or branch name
    let ticketId = this.extractTicketId(commitMessage);
    if (!ticketId) {
      ticketId = this.extractTicketId(this.branch);
    }

    let ticket = null;

    if (ticketId && this.jiraClient) {
      try {
        ticket = await this.jiraClient.getTicket(ticketId);
      } catch (error: any) {
        console.warn(`Could not fetch Jira ticket ${ticketId}:`, error.message);
      }
    }

    // Get changed files
    const files = this.getChangedFiles();

    return {
      pr: {
        number: 1, // Simulated PR number
        title,
        description,
        branch: this.branch,
        base_branch: this.baseBranch
      },
      ticket,
      files
    };
  }

  /**
   * Get commit message from branch HEAD
   */
  private getCommitMessage(): string {
    try {
      const message = execSync(
        `git log -1 --pretty=format:"%s%n%n%b"`,
        {
          cwd: this.repoPath,
          encoding: 'utf-8'
        }
      );
      return message.trim();
    } catch (error: any) {
      throw new Error(`Failed to get commit message: ${error.message}`);
    }
  }

  /**
   * Parse commit message into title and description
   */
  private parseCommitMessage(message: string): { title: string; description: string } {
    const lines = message.split('\n');
    const title = lines[0] || '';
    const description = lines.slice(1).join('\n').trim();
    return { title, description };
  }

  /**
   * Extract ticket ID from commit message
   */
  private extractTicketId(message: string): string | null {
    // Look for patterns like PB-123, PROJ-456, etc.
    const match = message.match(/([A-Z]+-\d+)/);
    return match ? match[1]! : null;
  }

  /**
   * Get list of changed files with content
   */
  private getChangedFiles(): FileChange[] {
    const files: FileChange[] = [];

    try {
      // Get list of changed files
      const changedFilesOutput = execSync(
        `git diff --name-status ${this.baseBranch}...${this.branch}`,
        {
          cwd: this.repoPath,
          encoding: 'utf-8'
        }
      );

      const lines = changedFilesOutput.trim().split('\n').filter(l => l);

      for (const line of lines) {
        const [status, filePath] = line.split('\t');
        if (!filePath) continue;

        let fileStatus: FileChange['status'];
        switch (status) {
          case 'A':
            fileStatus = 'added';
            break;
          case 'M':
            fileStatus = 'modified';
            break;
          case 'D':
            fileStatus = 'deleted';
            break;
          case 'R':
            fileStatus = 'renamed';
            break;
          default:
            fileStatus = 'modified';
        }

        // Get file content (if not deleted)
        let content: string | undefined;
        if (fileStatus !== 'deleted') {
          try {
            // Use git show to get content from the branch
            content = execSync(
              `git show ${this.branch}:"${filePath}"`,
              {
                cwd: this.repoPath,
                encoding: 'utf-8'
              }
            );
          } catch (error: any) {
            console.warn(`Could not read file ${filePath} from branch ${this.branch}:`, error.message);
          }
        }

        // Get additions/deletions count
        const { additions, deletions } = this.getFileStats(filePath);

        files.push({
          path: filePath,
          status: fileStatus,
          additions,
          deletions,
          content
        });
      }

      return files;
    } catch (error: any) {
      throw new Error(`Failed to get changed files: ${error.message}`);
    }
  }

  /**
   * Get file statistics (additions/deletions)
   */
  private getFileStats(filePath: string): { additions: number; deletions: number } {
    try {
      const stats = execSync(
        `git diff --numstat ${this.baseBranch}...${this.branch} -- "${filePath}"`,
        {
          cwd: this.repoPath,
          encoding: 'utf-8'
        }
      );

      const match = stats.trim().match(/^(\d+)\s+(\d+)/);
      if (match) {
        return {
          additions: parseInt(match[1]!, 10),
          deletions: parseInt(match[2]!, 10)
        };
      }

      return { additions: 0, deletions: 0 };
    } catch (error) {
      return { additions: 0, deletions: 0 };
    }
  }

  /**
   * Get full diff for context
   */
  getDiff(): string {
    try {
      return execSync(
        `git diff ${this.baseBranch}...${this.branch}`,
        {
          cwd: this.repoPath,
          encoding: 'utf-8'
        }
      );
    } catch (error) {
      return '';
    }
  }
}