import { spawn } from 'node:child_process';
import { resolve } from 'node:path';
import { z } from 'zod';
import type { ToolDef } from '../types.js';
import type { CodecontextResponse } from '../../codecontext_client.js';

// ======================= MCP Client =======================

const BOOCONTEXT_PATH = resolve('/opt/forks/boocontext/dist/standalone.js');
const TOOL_CALL_TIMEOUT_MS = 60_000;

interface JsonRpcMessage {
  jsonrpc: '2.0';
  id?: number | string;
  result?: {
    content?: Array<{ type: string; text: string }>;
  };
  error?: { code?: number; message: string };
}

/**
 * Single-shot MCP JSON-RPC client for boocontext.
 * Spawns the process, sends initialize + tools/call over NDJSON, returns the
 * text result from the content array.  The boocontext MCP server auto-detects
 * newline-delimited JSON transport when the first input lacks Content-Length
 * headers, which is exactly what we send.
 */
async function callBoocontext(
  toolName: string,
  args: Record<string, unknown>,
): Promise<string> {
  return new Promise<string>((resolvePromise, reject) => {
    const child = spawn(process.execPath, [BOOCONTEXT_PATH], {
      stdio: ['pipe', 'pipe', 'pipe'],
      timeout: TOOL_CALL_TIMEOUT_MS,
    });

    let stdout = '';
    let stderr = '';
    let resolved = false;

    function finalize(err?: Error, result?: string): void {
      if (resolved) return;
      resolved = true;
      if (err) reject(err);
      else resolvePromise(result!);
      child.kill();
    }

    child.stdout!.on('data', (chunk: Buffer) => {
      stdout += chunk.toString();
    });

    child.stderr!.on('data', (chunk: Buffer) => {
      stderr += chunk.toString();
    });

    child.on('error', (err: Error) => {
      finalize(new Error(`boocontext spawn error: ${err.message}`));
    });

    child.on('close', (code: number | null) => {
      if (resolved) return;

      // Parse newline-delimited JSON responses from stdout
      const lines = stdout.split('\n').filter((l) => l.trim().length > 0);
      let toolText: string | undefined;
      let toolError: string | undefined;

      for (const line of lines) {
        try {
          const msg = JSON.parse(line) as JsonRpcMessage;
          if (msg.id === 2) {
            if (msg.error) {
              toolError = msg.error.message ?? 'boocontext tool call failed';
            } else if (msg.result?.content?.[0]?.text !== undefined) {
              toolText = msg.result.content[0].text;
            }
          }
        } catch {
          // skip malformed JSON lines
        }
      }

      if (toolError) {
        finalize(new Error(toolError));
      } else if (toolText !== undefined) {
        finalize(undefined, toolText);
      } else {
        const errSuffix =
          stderr.length > 0 ? ` stderr: ${stderr.slice(0, 500)}` : '';
        finalize(
          new Error(`boocontext MCP call failed (exit ${code})${errSuffix}`),
        );
      }
    });

    // Step 1: initialize — establishes MCP protocol version + capabilities
    child.stdin!.write(
      JSON.stringify({
        jsonrpc: '2.0',
        id: 1,
        method: 'initialize',
        params: {
          protocolVersion: '2024-11-05',
          capabilities: {},
          clientInfo: { name: 'boocode-server', version: '1.0.0' },
        },
      }) + '\n',
    );

    // Step 2: tools/call — invoke the named boocontext tool
    child.stdin!.write(
      JSON.stringify({
        jsonrpc: '2.0',
        id: 2,
        method: 'tools/call',
        params: { name: toolName, arguments: args },
      }) + '\n',
    );

    child.stdin!.end();

    // Safety timeout — prevent hung processes
    setTimeout(() => {
      finalize(
        new Error(
          `boocontext call timed out after ${TOOL_CALL_TIMEOUT_MS}ms`,
        ),
      );
    }, TOOL_CALL_TIMEOUT_MS);
  });
}

// ======================= Tool Definition =======================

const TRUNCATION_LIMIT = 32_000;

export const GetCodeImpactInput = z.object({
  symbol: z.string().min(1).describe('Symbol name for TSA trace_impact'),
  file: z.string().optional().describe('File path for codesight blast_radius'),
  directory: z
    .string()
    .optional()
    .describe('Directory (defaults to project root)'),
  depth: z
    .number()
    .int()
    .min(1)
    .max(5)
    .optional()
    .describe('Max blast-radius traversal depth (default 1)'),
});
export type GetCodeImpactInputT = z.infer<typeof GetCodeImpactInput>;

const DESCRIPTION =
  'Impact analysis. Merges symbol-level call trace with file-level blast radius. ' +
  'Use before making changes to understand change propagation. ' +
  'Single call replaces separate get_symbol_info + get_blast_radius steps.';

/**
 * Standalone execute function — calls the boocontext MCP `boocontext_impact`
 * tool via a short-lived child process, then wraps the result in the standard
 * CodecontextResponse shape with inline truncation at 32 KB.
 */
export async function executeGetCodeImpact(
  input: GetCodeImpactInputT,
  projectPath: string,
): Promise<CodecontextResponse> {
  const args: Record<string, unknown> = {
    symbol: input.symbol,
    directory: input.directory ?? projectPath,
  };
  if (input.file) args['file'] = input.file;

  const text = await callBoocontext('boocontext_impact', args);

  // Inline truncation matching codecontext_client.ts patterns (32 KB ceiling).
  if (text.length > TRUNCATION_LIMIT) {
    const sliced = text.slice(0, TRUNCATION_LIMIT);
    const omitted = text.length - TRUNCATION_LIMIT;
    return {
      result: `${sliced}\n\n[truncated, ${omitted} chars omitted; narrow with symbol or file parameters]`,
      truncated: true,
    };
  }

  return { result: text, truncated: false };
}

export const getCodeImpact: ToolDef<GetCodeImpactInputT> = {
  name: 'get_code_impact',
  description: DESCRIPTION,
  inputSchema: GetCodeImpactInput,
  jsonSchema: {
    type: 'function',
    function: {
      name: 'get_code_impact',
      description: DESCRIPTION,
      parameters: {
        type: 'object',
        properties: {
          symbol: {
            type: 'string',
            description: 'Symbol name for TSA trace_impact',
          },
          file: {
            type: 'string',
            description: 'File path for codesight blast_radius',
          },
          directory: {
            type: 'string',
            description: 'Directory (defaults to project root)',
          },
          depth: {
            type: 'number',
            description: 'Max blast-radius traversal depth (default 1)',
          },
        },
        required: ['symbol'],
        additionalProperties: false,
      },
    },
  },
  execute(input, projectRoot) {
    return executeGetCodeImpact(input, projectRoot);
  },
};