import type { KeyLike } from "node:crypto";
import {
  canonicalJsonDigest,
  assertWellFormedNfcString,
  isSha256Hex,
  parseCanonicalJson,
  verifyEd25519Envelope,
} from "./canonical-digest.ts";

export interface ApprovalPayload {
  schema: "portfolio-approval-payload/v1";
  keyId: string;
  issuerEpoch: number;
  authorizedRole: string;
  evidenceFingerprints: string[];
  recordClass: "content" | "asset";
  recordType: string;
  publicRecordIdOrAssetId: string;
  approvedPublicRecordHashOrManifestRecordHash: string;
  sanitizedOutputHashOrNull: string | null;
  decision: "approve" | "reject" | "revoke";
  issuedAt: string;
  expiresAt: string;
  previousLedgerHeadHash: string;
  ledgerRevision: number;
  policyVersion: string;
}

export interface ApprovalEnvelope {
  schema: "portfolio-approval-envelope/v1";
  payload: ApprovalPayload;
  signature: {
    algorithm: "Ed25519";
    encoding: "base64url-nopad";
    value: string;
  };
}

export interface ApprovalTrustKey {
  keyId: string;
  issuerEpoch: number;
  scope: "portfolio-approval-decision/v1";
  authorizedRoles: string[];
  publicKey: KeyLike;
  revoked?: boolean;
}

export interface ApprovalTrustPolicy {
  now: string;
  latestLedgerHeadHash: string;
  latestLedgerRevision: number;
  trustedKeys: ApprovalTrustKey[];
  ledgerProof: ApprovalLedgerProof;
}

export interface ApprovalLedgerProof {
  schema: "portfolio-approval-ledger-proof/v1";
  genesisHeadHash: string;
  entries: ApprovalEnvelope[];
}

const payloadKeys = [
  "schema",
  "keyId",
  "issuerEpoch",
  "authorizedRole",
  "evidenceFingerprints",
  "recordClass",
  "recordType",
  "publicRecordIdOrAssetId",
  "approvedPublicRecordHashOrManifestRecordHash",
  "sanitizedOutputHashOrNull",
  "decision",
  "issuedAt",
  "expiresAt",
  "previousLedgerHeadHash",
  "ledgerRevision",
  "policyVersion",
] as const;
const envelopeKeys = ["schema", "payload", "signature"] as const;
const signatureKeys = ["algorithm", "encoding", "value"] as const;
const utcTimestamp = /^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(?:\.\d{1,3})?Z$/u;
const safeToken = /^[A-Za-z0-9][A-Za-z0-9._/-]{0,127}$/u;

function record(value: unknown, label: string): Record<string, unknown> {
  if (value === null || typeof value !== "object" || Array.isArray(value))
    throw new Error(`${label} must be an object.`);
  return value as Record<string, unknown>;
}

function exactKeys(
  value: Record<string, unknown>,
  keys: readonly string[],
  label: string,
): void {
  const actual = Object.keys(value).sort();
  const expected = [...keys].sort();
  if (
    actual.length !== expected.length ||
    actual.some((key, index) => key !== expected[index])
  ) {
    throw new Error(`${label} contains missing or unknown fields.`);
  }
}

function validTimestamp(
  value: unknown,
  label: string,
): asserts value is string {
  if (
    typeof value !== "string" ||
    !utcTimestamp.test(value) ||
    Number.isNaN(Date.parse(value))
  ) {
    throw new Error(`${label} must be a UTC RFC 3339 timestamp.`);
  }
}

export function validateApprovalEnvelope(value: unknown): ApprovalEnvelope {
  const outer = record(value, "approval envelope");
  exactKeys(outer, envelopeKeys, "approval envelope");
  if (outer.schema !== "portfolio-approval-envelope/v1")
    throw new Error("Approval envelope schema is invalid.");
  const payload = record(outer.payload, "approval payload");
  exactKeys(payload, payloadKeys, "approval payload");
  const signature = record(outer.signature, "approval signature");
  exactKeys(signature, signatureKeys, "approval signature");

  if (payload.schema !== "portfolio-approval-payload/v1")
    throw new Error("Approval payload schema is invalid.");
  for (const key of [
    "keyId",
    "authorizedRole",
    "publicRecordIdOrAssetId",
    "policyVersion",
  ] as const) {
    const field = payload[key];
    if (typeof field !== "string" || !safeToken.test(field))
      throw new Error(`${key} is invalid.`);
    assertWellFormedNfcString(field, key);
  }
  if (
    !Number.isSafeInteger(payload.issuerEpoch) ||
    (payload.issuerEpoch as number) < 1
  )
    throw new Error("issuerEpoch is invalid.");
  if (
    !Number.isSafeInteger(payload.ledgerRevision) ||
    (payload.ledgerRevision as number) < 0
  )
    throw new Error("ledgerRevision is invalid.");
  if (payload.recordClass !== "content" && payload.recordClass !== "asset")
    throw new Error("recordClass is invalid.");
  if (typeof payload.recordType !== "string")
    throw new Error("recordType is invalid.");
  assertWellFormedNfcString(payload.recordType, "recordType");
  if (payload.recordClass === "content" && !safeToken.test(payload.recordType))
    throw new Error("Content recordType is required.");
  if (payload.recordClass === "asset" && payload.recordType !== "")
    throw new Error("Asset recordType must be empty.");
  if (
    !isSha256Hex(payload.approvedPublicRecordHashOrManifestRecordHash) ||
    !isSha256Hex(payload.previousLedgerHeadHash)
  ) {
    throw new Error("Approval hash field is invalid.");
  }
  if (
    !Array.isArray(payload.evidenceFingerprints) ||
    payload.evidenceFingerprints.length === 0 ||
    payload.evidenceFingerprints.some((item) => !isSha256Hex(item)) ||
    new Set(payload.evidenceFingerprints).size !==
      payload.evidenceFingerprints.length
  ) {
    throw new Error(
      "evidenceFingerprints must be a unique, non-empty digest list.",
    );
  }
  if (
    payload.recordClass === "content" &&
    payload.sanitizedOutputHashOrNull !== null
  )
    throw new Error("Content approval cannot bind sanitized bytes.");
  if (
    payload.recordClass === "asset" &&
    !isSha256Hex(payload.sanitizedOutputHashOrNull)
  )
    throw new Error("Asset approval must bind sanitized bytes.");
  if (!["approve", "reject", "revoke"].includes(payload.decision as string))
    throw new Error("Decision is invalid.");
  validTimestamp(payload.issuedAt, "issuedAt");
  validTimestamp(payload.expiresAt, "expiresAt");
  if (Date.parse(payload.issuedAt) >= Date.parse(payload.expiresAt))
    throw new Error("Approval expiry must follow issue time.");
  if (
    signature.algorithm !== "Ed25519" ||
    signature.encoding !== "base64url-nopad" ||
    typeof signature.value !== "string"
  ) {
    throw new Error("Approval signature metadata is invalid.");
  }
  return outer as unknown as ApprovalEnvelope;
}

export function parseApprovalEnvelopeJson(
  source: string | Uint8Array,
): ApprovalEnvelope {
  return validateApprovalEnvelope(parseCanonicalJson(source));
}

function verifyEnvelopeSignature(
  envelopeValue: unknown,
  trust: ApprovalTrustPolicy,
): ApprovalEnvelope {
  const envelope = validateApprovalEnvelope(envelopeValue);
  const matchingKeys = trust.trustedKeys.filter(
    (candidate) =>
      candidate.keyId === envelope.payload.keyId &&
      candidate.issuerEpoch === envelope.payload.issuerEpoch,
  );
  if (matchingKeys.length !== 1)
    throw new Error(
      "Approval trust policy must contain exactly one matching key epoch.",
    );
  const key = matchingKeys[0];
  if (
    key === undefined ||
    key.revoked ||
    key.scope !== "portfolio-approval-decision/v1"
  )
    throw new Error("Approval key, scope, or epoch is not trusted.");
  if (!key.authorizedRoles.includes(envelope.payload.authorizedRole))
    throw new Error("Approval role is not authorized.");
  verifyEd25519Envelope(envelope, key);
  return envelope;
}

function typedDecisionId(payload: ApprovalPayload): string {
  return `${payload.recordClass}\0${payload.recordType}\0${payload.publicRecordIdOrAssetId}`;
}

export function verifyApprovalLedger(
  trust: ApprovalTrustPolicy,
): Map<string, ApprovalEnvelope> {
  validTimestamp(trust.now, "trusted now");
  if (
    !isSha256Hex(trust.latestLedgerHeadHash) ||
    !Number.isSafeInteger(trust.latestLedgerRevision) ||
    trust.latestLedgerRevision < 0
  ) {
    throw new Error("Protected live-ledger state is invalid.");
  }
  const proof = trust.ledgerProof;
  if (
    proof === null ||
    typeof proof !== "object" ||
    Array.isArray(proof) ||
    JSON.stringify(Object.keys(proof).sort()) !==
      JSON.stringify(["entries", "genesisHeadHash", "schema"]) ||
    proof.schema !== "portfolio-approval-ledger-proof/v1" ||
    !isSha256Hex(proof.genesisHeadHash) ||
    !Array.isArray(proof.entries) ||
    proof.entries.length !== trust.latestLedgerRevision
  )
    throw new Error("Authenticated approval ledger proof is incomplete.");
  let head = proof.genesisHeadHash;
  const latest = new Map<string, ApprovalEnvelope>();
  proof.entries.forEach((raw, index) => {
    const envelope = verifyEnvelopeSignature(raw, trust);
    const revision = index + 1;
    if (
      envelope.payload.ledgerRevision !== revision ||
      envelope.payload.previousLedgerHeadHash !== head ||
      Date.parse(envelope.payload.issuedAt) > Date.parse(trust.now)
    )
      throw new Error(
        "Approval ledger chain is not contiguous through the protected revision.",
      );
    const envelopeDigest = canonicalJsonDigest(
      "portfolio-approval-envelope-digest/v1",
      envelope,
    );
    head = canonicalJsonDigest("portfolio-approval-ledger-entry/v1", {
      previousLedgerHeadHash: head,
      ledgerRevision: revision,
      envelopeDigest,
    });
    latest.set(typedDecisionId(envelope.payload), envelope);
  });
  if (head !== trust.latestLedgerHeadHash)
    throw new Error(
      "Approval ledger proof does not authenticate the protected head.",
    );
  return latest;
}

export function verifyApprovalEnvelope(
  envelopeValue: unknown,
  trust: ApprovalTrustPolicy,
): ApprovalPayload {
  const envelope = verifyEnvelopeSignature(envelopeValue, trust);
  const latest = verifyApprovalLedger(trust).get(
    typedDecisionId(envelope.payload),
  );
  if (
    latest === undefined ||
    canonicalJsonDigest("portfolio-approval-envelope-digest/v1", latest) !==
      canonicalJsonDigest("portfolio-approval-envelope-digest/v1", envelope)
  ) {
    throw new Error(
      "Approval is not the latest authenticated decision for this record.",
    );
  }
  if (
    Date.parse(trust.now) < Date.parse(envelope.payload.issuedAt) ||
    Date.parse(trust.now) >= Date.parse(envelope.payload.expiresAt)
  ) {
    throw new Error("Approval is not current at the trusted time.");
  }
  if (envelope.payload.decision !== "approve")
    throw new Error("The latest decision is reject/revoke, not approval.");
  return envelope.payload;
}