/**
 * Sanitized reference implementation of a fail-closed release gate.
 *
 * This module contains no customer source, secrets, signing keys, proprietary
 * schemas, or production endpoints. I/O and cryptographic verification belong
 * in adapters. The gate consumes their evidence and makes one deterministic
 * decision: a candidate is ready, or it is rejected with explicit reasons.
 */

export type ReleaseStatus = "ready" | "rejected";

export type CheckCode =
  | "candidate_identity"
  | "target_region"
  | "artifact_signature"
  | "artifact_hash"
  | "content_schema"
  | "content_age"
  | "runtime_proof"
  | "dependency_budget"
  | "smoke_tests"
  | "rollback_target";

export type ReleaseManifest = {
  revision: string;
  buildId: string;
  region: string;
  schemaVersion: number;
  createdAt: string;
  runtimeProofs: readonly string[];
  dependencyBytes: number;
};

export type VerificationEvidence = {
  candidateRevision: string;
  signatureValid: boolean;
  hashMatches: boolean;
  smokeTests: readonly {
    name: string;
    passed: boolean;
  }[];
  rollbackTargetAvailable: boolean;
};

export type ReleasePolicy = {
  expectedRegion: string;
  allowedSchemaVersions: readonly number[];
  maxContentAgeMs: number;
  requiredRuntime: string;
  dependencyBudgetBytes: number;
  requireRollbackTarget: boolean;
};

export type ReleaseCheck = {
  code: CheckCode;
  label: string;
  passed: boolean;
  detail: string;
};

export type ReleaseDecision = {
  status: ReleaseStatus;
  checks: readonly ReleaseCheck[];
  failedCodes: readonly CheckCode[];
  evaluatedAt: string;
};

function check(
  code: CheckCode,
  label: string,
  passed: boolean,
  detail: string,
): ReleaseCheck {
  return { code, label, passed, detail };
}

function formatBytes(bytes: number): string {
  return `${(bytes / 1024 / 1024).toFixed(1)} MB`;
}

export function evaluateRelease(
  manifest: ReleaseManifest,
  evidence: VerificationEvidence,
  policy: ReleasePolicy,
  nowMs: number,
): ReleaseDecision {
  const createdAtMs = Date.parse(manifest.createdAt);
  const contentAgeMs = nowMs - createdAtMs;
  const hasValidTimestamp = Number.isFinite(createdAtMs);
  const contentAgeIsValid =
    hasValidTimestamp &&
    contentAgeMs >= 0 &&
    contentAgeMs <= policy.maxContentAgeMs;
  const allSmokeTestsPass =
    evidence.smokeTests.length > 0 &&
    evidence.smokeTests.every((test) => test.passed);

  const checks: readonly ReleaseCheck[] = [
    check(
      "candidate_identity",
      "Candidate identity",
      manifest.revision.length > 0 &&
        manifest.buildId.length > 0 &&
        manifest.revision === evidence.candidateRevision,
      `manifest ${manifest.revision || "missing"} / evidence ${
        evidence.candidateRevision || "missing"
      }`,
    ),
    check(
      "target_region",
      "Target region",
      manifest.region === policy.expectedRegion,
      `${manifest.region} must equal ${policy.expectedRegion}`,
    ),
    check(
      "artifact_signature",
      "Artifact signature",
      evidence.signatureValid,
      evidence.signatureValid
        ? "cryptographic adapter reported a valid signature"
        : "signature evidence is missing or invalid",
    ),
    check(
      "artifact_hash",
      "Artifact hash",
      evidence.hashMatches,
      evidence.hashMatches
        ? "candidate bytes match the signed manifest"
        : "candidate bytes do not match the signed manifest",
    ),
    check(
      "content_schema",
      "Content schema",
      policy.allowedSchemaVersions.includes(manifest.schemaVersion),
      `schema v${manifest.schemaVersion}; allowed: ${policy.allowedSchemaVersions.join(
        ", ",
      )}`,
    ),
    check(
      "content_age",
      "Content age",
      contentAgeIsValid,
      hasValidTimestamp
        ? `${Math.max(0, Math.round(contentAgeMs / 60_000))} minutes old; limit ${Math.round(
            policy.maxContentAgeMs / 60_000,
          )}`
        : "manifest timestamp is invalid",
    ),
    check(
      "runtime_proof",
      "Runtime proof",
      manifest.runtimeProofs.includes(policy.requiredRuntime),
      `${policy.requiredRuntime} proof must be present`,
    ),
    check(
      "dependency_budget",
      "Dependency budget",
      manifest.dependencyBytes <= policy.dependencyBudgetBytes,
      `${formatBytes(manifest.dependencyBytes)} / ${formatBytes(
        policy.dependencyBudgetBytes,
      )}`,
    ),
    check(
      "smoke_tests",
      "Candidate smoke tests",
      allSmokeTestsPass,
      `${evidence.smokeTests.filter((test) => test.passed).length}/${
        evidence.smokeTests.length
      } checks passed`,
    ),
    check(
      "rollback_target",
      "Rollback target",
      !policy.requireRollbackTarget || evidence.rollbackTargetAvailable,
      evidence.rollbackTargetAvailable
        ? "previous verified artifact is available"
        : "no verified rollback target is available",
    ),
  ];

  const failedCodes = checks
    .filter((item) => !item.passed)
    .map((item) => item.code);

  return {
    status: failedCodes.length === 0 ? "ready" : "rejected",
    checks,
    failedCodes,
    evaluatedAt: new Date(nowMs).toISOString(),
  };
}