import { execFileSync, spawnSync } from "node:child_process";
import { existsSync, readFileSync } from "node:fs";
import path from "node:path";
import { fileURLToPath } from "node:url";

const SCRIPT_DIR = path.dirname(fileURLToPath(import.meta.url));
const ROOT = path.resolve(SCRIPT_DIR, "..");
const BASELINE_PATH = path.join(SCRIPT_DIR, "governance-baseline.json");

const MAX_FILE_LINES = 500;
const MAINTAINABILITY_RULES = [
  'complexity: ["error", { "max": 20 }]',
  'max-lines-per-function: ["error", { "skipComments": true, "max": 150 }]',
  'max-params: ["error", 4]',
  'max-depth: ["error", 4]',
];
const GOVERNED_ROOTS = ["src/", "config/"];
const EXCLUDE_DIR = /(^|\/)(mocks|test|__mocks__|node_modules|dist|coverage|e2e)\//;
const EXCLUDE_NAME = /\.(mock|test|spec)\.(ts|tsx)$|\.d\.ts$/;
// Repository-level gates that run after the source gates. Each is an npm
// script so it can also be run on its own.
const REPOSITORY_GATES = [
  ["Terraform import-plan contract", "test:terraform-import-plan"],
  ["Terraform release-plan contract", "test:terraform-release-plan"],
  ["Terraform isolation gate", "test:terraform-isolation"],
  ["Terraform formatting and validation", "test:terraform"],
  ["HCP run guard", "test:hcp-run-guard"],
  ["CloudFront release verify", "test:cloudfront-release-verify"],
  ["GitHub workflow shell", "test:github-workflows"],
];

function isGoverned(relativePath) {
  return (
    GOVERNED_ROOTS.some((root) => relativePath.startsWith(root)) &&
    /\.(ts|tsx)$/.test(relativePath) &&
    !EXCLUDE_DIR.test(relativePath) &&
    !EXCLUDE_NAME.test(relativePath)
  );
}

function gitText(args) {
  return execFileSync("git", args, { cwd: ROOT, encoding: "utf8" }).trim();
}

function gitLines(args) {
  return gitText(args).split("\n").filter(Boolean);
}

function governedFiles() {
  const tracked = gitLines(["ls-files"]);
  const untracked = gitLines(["ls-files", "--others", "--exclude-standard"]);
  return [...new Set([...tracked, ...untracked])].filter(
    (relativePath) => isGoverned(relativePath) && existsSync(path.join(ROOT, relativePath)),
  );
}

function lineCount(relativePath) {
  const content = readFileSync(path.join(ROOT, relativePath), "utf8");
  if (content.length === 0) return 0;
  return content.endsWith("\n") ? content.split("\n").length - 1 : content.split("\n").length;
}

function readBaseline() {
  return JSON.parse(readFileSync(BASELINE_PATH, "utf8"));
}

function readBaselineAtRef(ref) {
  try {
    const content = execFileSync("git", ["show", `${ref}:scripts/governance-baseline.json`], {
      cwd: ROOT,
      encoding: "utf8",
      stdio: ["ignore", "pipe", "ignore"],
    });
    return JSON.parse(content);
  } catch {
    return null;
  }
}

function godfileRatchet(baseRef) {
  const baseline = readBaseline();
  const cap = baseline.maxFileLines ?? MAX_FILE_LINES;
  const debtEntries = new Map(
    (baseline.godfileDebt ?? []).map((entry) => [entry.path, entry.maxLines]),
  );
  const files = governedFiles();

  const newDebt = [];
  const grownDebt = [];
  for (const file of files) {
    const lines = lineCount(file);
    const debtCap = debtEntries.get(file);
    if (lines > cap && debtCap === undefined) {
      newDebt.push({ path: file, lines });
    } else if (debtCap !== undefined && lines > debtCap) {
      grownDebt.push({ path: file, lines, maxLines: debtCap });
    }
  }

  const stale = [];
  const remaining = [];
  for (const [debtPath, maxLines] of debtEntries) {
    const lines = files.includes(debtPath) ? lineCount(debtPath) : -1;
    if (lines === -1 || lines <= cap) {
      stale.push({ path: debtPath, lines });
    } else {
      remaining.push({ path: debtPath, lines, maxLines });
    }
  }

  const baselineLoosening = [];
  const baseBaseline = baseRef ? readBaselineAtRef(baseRef) : null;
  if (baseBaseline) {
    const baseCap = baseBaseline.maxFileLines ?? MAX_FILE_LINES;
    if (cap > baseCap) {
      baselineLoosening.push(`global cap increased from ${baseCap} to ${cap}`);
    }
    const baseEntries = new Map(
      (baseBaseline.godfileDebt ?? []).map((entry) => [entry.path, entry.maxLines]),
    );
    for (const [debtPath, maxLines] of debtEntries) {
      const priorMax = baseEntries.get(debtPath);
      if (priorMax === undefined) {
        baselineLoosening.push(`new debt entry: ${debtPath}`);
      } else if (maxLines > priorMax) {
        baselineLoosening.push(`cap increased for ${debtPath}: ${priorMax} -> ${maxLines}`);
      }
    }
  }

  return {
    cap,
    newDebt,
    grownDebt,
    stale,
    remaining,
    baselineLoosening,
    comparedBaseline: Boolean(baseBaseline),
  };
}

function resolveBaseRef() {
  if (process.env.GOVERNANCE_BASE) return process.env.GOVERNANCE_BASE;
  if (process.env.GITHUB_BASE_REF) return `origin/${process.env.GITHUB_BASE_REF}`;
  for (const candidate of ["origin/dev", "origin/main"]) {
    try {
      execFileSync("git", ["rev-parse", "--verify", candidate], {
        cwd: ROOT,
        encoding: "utf8",
        stdio: "ignore",
      });
      return candidate;
    } catch {
      // candidate ref not present locally; try the next
    }
  }
  return null;
}

function changedGovernedFiles(baseRef) {
  let mergeBase;
  try {
    mergeBase = execFileSync("git", ["merge-base", baseRef, "HEAD"], {
      cwd: ROOT,
      encoding: "utf8",
      stdio: ["ignore", "pipe", "ignore"],
    }).trim();
  } catch {
    return null;
  }
  const diffed = gitLines(["diff", "--name-only", "--diff-filter=AMR", mergeBase, "HEAD"]);
  const untracked = gitLines(["ls-files", "--others", "--exclude-standard"]);
  return [...new Set([...diffed, ...untracked])].filter(isGoverned);
}

function maintainabilityGate(files) {
  if (files.length === 0) {
    return { skipped: true, reason: "no changed governed TS/TSX files" };
  }
  // Invoke eslint via node so Windows (no shebang exec) and Unix both work.
  const eslintJs = path.join(ROOT, "node_modules", "eslint", "bin", "eslint.js");
  const ruleArgs = MAINTAINABILITY_RULES.flatMap((rule) => ["--rule", rule]);
  const result = spawnSync(
    process.execPath,
    [
      eslintJs,
      ...files,
      ...ruleArgs,
      "--max-warnings=0",
      "--no-warn-ignored",
      "--no-error-on-unmatched-pattern",
    ],
    { cwd: ROOT, encoding: "utf8" },
  );
  return {
    skipped: false,
    status: result.status,
    stdout: result.stdout?.trim() ?? "",
    stderr: result.stderr?.trim() ?? "",
    files,
  };
}

function plural(count, word) {
  return `${count} ${word}${count === 1 ? "" : "s"}`;
}

function runRepositoryGate(label, script) {
  // Reuse the npm that launched us when available (matches its version and
  // config); fall back to PATH for direct `node scripts/governance-check.mjs`.
  const npmCli = process.env.npm_execpath;
  const executable = npmCli ? process.execPath : "npm";
  const args = npmCli ? [npmCli, "run", script] : ["run", script];
  const result = spawnSync(executable, args, {
    cwd: ROOT,
    encoding: "utf8",
    stdio: "inherit",
  });
  return { label, status: result.status, error: result.error };
}

function main() {
  const failures = [];
  const baseRef = resolveBaseRef();
  if (!baseRef) {
    failures.push(
      "base ref is required but was not found. Set GOVERNANCE_BASE to a valid commit or fetch origin/dev.",
    );
  } else {
    try {
      gitText(["merge-base", baseRef, "HEAD"]);
    } catch {
      failures.push(
        `base ref '${baseRef}' cannot be resolved against HEAD. Fetch it or set GOVERNANCE_BASE correctly.`,
      );
    }
  }

  console.log("─".repeat(64));
  console.log("godfile ratchet: legacy caps may only shrink");
  const god = godfileRatchet(baseRef);
  console.log(
    `  cap: ${god.cap} lines | grandfathered debt: ${plural(god.remaining.length, "file")} | new violations: ${god.newDebt.length}`,
  );
  for (const entry of god.remaining) {
    console.log(`    debt   ${String(entry.lines).padStart(4)}/${entry.maxLines}  ${entry.path}`);
  }
  for (const entry of god.newDebt) {
    console.log(`    NEW    ${String(entry.lines).padStart(4)}  ${entry.path}`);
  }
  for (const entry of god.grownDebt) {
    console.log(`    GREW   ${String(entry.lines).padStart(4)}/${entry.maxLines}  ${entry.path}`);
  }
  if (god.newDebt.length > 0) {
    failures.push(
      `godfile ratchet: ${plural(god.newDebt.length, "file")} exceed ${god.cap} lines. Refactor them under the cap; new baseline debt is forbidden.`,
    );
  }
  if (god.grownDebt.length > 0) {
    failures.push(
      `godfile ratchet: ${plural(god.grownDebt.length, "grandfathered file")} exceeded its frozen line cap.`,
    );
  }
  if (god.baselineLoosening.length > 0) {
    failures.push(
      `governance baseline was loosened: ${god.baselineLoosening.join("; ")}. Only cap reductions and entry removals are allowed.`,
    );
  }
  if (!god.comparedBaseline) {
    console.log("  baseline comparison unavailable (initial adoption or missing base file)");
  }
  if (god.stale.length > 0) {
    console.log(`  stale baseline entries (now compliant — remove to ratchet tighter):`);
    for (const entry of god.stale) {
      console.log(`    stale  ${entry.path}`);
    }
  }

  console.log("─".repeat(64));
  if (!baseRef) {
    console.log("changed-file maintainability gate: FAIL (no valid base ref)");
  } else {
    const files = changedGovernedFiles(baseRef);
    console.log(
      `changed-file maintainability gate (base: ${baseRef}): ${files === null ? "unresolvable" : plural(files.length, "changed governed file")}`,
    );
    if (files === null) {
      console.log("  failed — base ref could not be resolved against HEAD");
    } else {
      const gate = maintainabilityGate(files);
      if (gate.skipped) {
        console.log(`  skipped — ${gate.reason}`);
      } else {
        const clean = gate.status === 0;
        console.log(
          `  result: ${clean ? "PASS" : "FAIL"} (complexity<=20, function<=150 lines, params<=4, depth<=4)`,
        );
        if (!clean) {
          if (gate.stdout) console.log(gate.stdout);
          if (gate.stderr) console.log(gate.stderr);
          failures.push(
            "changed-file maintainability gate: see ESLint output above. Extract functions/components to meet the thresholds; do not relax the thresholds.",
          );
        }
      }
    }
  }

  for (const [label, script] of REPOSITORY_GATES) {
    console.log("─".repeat(64));
    console.log(`${label}: npm run ${script}`);
    const gate = runRepositoryGate(label, script);
    if (gate.error) {
      failures.push(`${label}: could not start: ${gate.error.message}`);
    } else if (gate.status !== 0) {
      failures.push(`${label}: failed with exit code ${gate.status ?? "unknown"}`);
    }
  }

  console.log("─".repeat(64));
  if (failures.length > 0) {
    console.log(`RESULT: FAIL (${plural(failures.length, "gate")})`);
    for (const failure of failures) console.log(`  - ${failure}`);
    process.exit(1);
  }
  console.log("RESULT: PASS — all governance gates green");
}

main();