import assert from "node:assert/strict";
import { spawnSync } from "node:child_process";
import fs from "node:fs";
import os from "node:os";
import path from "node:path";
import test from "node:test";
import { fileURLToPath } from "node:url";

const scriptDir = path.dirname(fileURLToPath(import.meta.url));
const repoRoot = path.resolve(scriptDir, "..");
const mergeScript = path.join(scriptDir, "merge-managed-mcp-config.mjs");
const vscodeTemplateFile = path.join(
  repoRoot,
  "config",
  "mcp",
  "vscode.mcp.template.jsonc",
);
const copilotCliTemplateFile = path.join(
  repoRoot,
  "config",
  "mcp",
  "copilot-cli.mcp.template.jsonc",
);

function stripJsonComments(input) {
  let output = "";
  let inString = false;
  let escaping = false;
  let inLineComment = false;
  let inBlockComment = false;

  for (let index = 0; index < input.length; index += 1) {
    const char = input[index];
    const next = input[index + 1];

    if (inLineComment) {
      if (char === "\n") {
        inLineComment = false;
        output += char;
      }
      continue;
    }

    if (inBlockComment) {
      if (char === "*" && next === "/") {
        inBlockComment = false;
        index += 1;
      } else if (char === "\n" || char === "\r") {
        output += char;
      }
      continue;
    }

    if (inString) {
      output += char;
      if (escaping) {
        escaping = false;
      } else if (char === "\\") {
        escaping = true;
      } else if (char === '"') {
        inString = false;
      }
      continue;
    }

    if (char === '"') {
      inString = true;
      output += char;
      continue;
    }

    if (char === "/" && next === "/") {
      inLineComment = true;
      index += 1;
      continue;
    }

    if (char === "/" && next === "*") {
      inBlockComment = true;
      index += 1;
      continue;
    }

    output += char;
  }

  return output;
}

function stripTrailingCommas(input) {
  let output = "";
  let inString = false;
  let escaping = false;

  for (let index = 0; index < input.length; index += 1) {
    const char = input[index];

    if (inString) {
      output += char;
      if (escaping) {
        escaping = false;
      } else if (char === "\\") {
        escaping = true;
      } else if (char === '"') {
        inString = false;
      }
      continue;
    }

    if (char === '"') {
      inString = true;
      output += char;
      continue;
    }

    if (char === ",") {
      let lookahead = index + 1;
      while (lookahead < input.length && /\s/.test(input[lookahead])) {
        lookahead += 1;
      }
      if (input[lookahead] === "}" || input[lookahead] === "]") {
        continue;
      }
    }

    output += char;
  }

  return output;
}

function parseJsonc(input) {
  return JSON.parse(stripTrailingCommas(stripJsonComments(input)));
}

function runMerge({ targetFile, templateFile, serverKey, overridesFile }) {
  const args = [
    mergeScript,
    "--target",
    targetFile,
    "--template",
    templateFile,
    "--server-key",
    serverKey,
    "--set",
    "COPILOT_RESOURCES_HOME=/repo/home",
  ];

  if (overridesFile) {
    args.push("--overrides", overridesFile);
  }

  return spawnSync(process.execPath, args, {
    cwd: repoRoot,
    encoding: "utf8",
  });
}

test("preserves comments and custom servers while pruning stale managed MCP entries", () => {
  const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "copilot-mcp-"));
  const targetFile = path.join(tempDir, "mcp.json");

  fs.writeFileSync(
    targetFile,
    `{
  // keep this comment
  "servers": {
    // custom server stays
    "customServer": {
      "type": "http",
      "url": "https://example.com/mcp"
    },
    "gitea": {
      "type": "stdio",
      "command": "docker",
      "args": ["stale"]
    }
  }
}
`,
    "utf8",
  );

  const result = runMerge({
    targetFile,
    templateFile: vscodeTemplateFile,
    serverKey: "servers",
  });
  assert.equal(result.status, 0, result.stderr);

  const output = fs.readFileSync(targetFile, "utf8");
  assert.match(output, /\/\/ keep this comment/);
  assert.match(output, /\/\/ custom server stays/);
  assert.match(output, /"customServer"/);
  assert.match(output, /"playwright"/);
  assert.match(output, /"filesystem"/);
  assert.doesNotMatch(output, /"gitea"/);

  const parsed = parseJsonc(output);
  assert.equal(parsed.servers.customServer.type, "http");
  assert.equal(parsed.servers.playwright.command, "npx");
  assert.equal(parsed.servers.filesystem.command, "docker");
  assert.equal(parsed.servers.gitea, undefined);
});

test("creates managed MCP config from an empty target file", () => {
  const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "copilot-mcp-"));
  const targetFile = path.join(tempDir, "mcp.json");

  fs.writeFileSync(targetFile, "", "utf8");

  const result = runMerge({
    targetFile,
    templateFile: vscodeTemplateFile,
    serverKey: "servers",
  });
  assert.equal(result.status, 0, result.stderr);

  const output = fs.readFileSync(targetFile, "utf8");
  const parsed = parseJsonc(output);
  assert.equal(parsed.servers.playwright.command, "npx");
  assert.equal(parsed.servers.filesystem.command, "docker");
});

test("renders optional Gitea config when local overrides are complete", () => {
  const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "copilot-mcp-"));
  const targetFile = path.join(tempDir, "mcp-config.json");
  const overridesFile = path.join(tempDir, "mcp.local.jsonc");

  fs.writeFileSync(
    overridesFile,
    `{
  "servers": {
    "gitea": {
      "enabled": true,
      "serverUrl": "https://git.example.com",
      "token": "secret-token"
    }
  }
}
`,
    "utf8",
  );

  const result = runMerge({
    targetFile,
    templateFile: copilotCliTemplateFile,
    serverKey: "mcpServers",
    overridesFile,
  });
  assert.equal(result.status, 0, result.stderr);

  const parsed = parseJsonc(fs.readFileSync(targetFile, "utf8"));
  assert.equal(
    parsed.mcpServers.filesystem.args[0],
    "/repo/home/install/mcp/copilot-cli-filesystem-wrapper.mjs",
  );
  assert.equal(parsed.mcpServers.gitea.env.FORGEJOMCP_SERVER, "https://git.example.com");
  assert.equal(parsed.mcpServers.gitea.env.FORGEJOMCP_TOKEN, "secret-token");
  assert.equal(parsed.mcpServers.playwright, undefined);
});

test("second run is idempotent and keeps the file text unchanged", () => {
  const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "copilot-mcp-"));
  const targetFile = path.join(tempDir, "mcp.json");

  fs.writeFileSync(
    targetFile,
    `{
  // user comment
  "servers": {
    "customServer": {
      "type": "http",
      "url": "https://example.com/mcp"
    }
  }
}
`,
    "utf8",
  );

  const firstRun = runMerge({
    targetFile,
    templateFile: vscodeTemplateFile,
    serverKey: "servers",
  });
  assert.equal(firstRun.status, 0, firstRun.stderr);
  const firstOutput = fs.readFileSync(targetFile, "utf8");

  const secondRun = runMerge({
    targetFile,
    templateFile: vscodeTemplateFile,
    serverKey: "servers",
  });
  assert.equal(secondRun.status, 0, secondRun.stderr);
  assert.match(secondRun.stdout, /already up to date/);

  const secondOutput = fs.readFileSync(targetFile, "utf8");
  assert.equal(secondOutput, firstOutput);
  assert.match(secondOutput, /\/\/ user comment/);
});