import type { EkklesiaUserId, GrantId, PermissionId } from "@ekklesia/contracts";
import {
  createUserActor,
  isAuthenticatedPrincipal,
  safeParseEkklesiaUserId,
  safeParseGrantId,
  safeParsePermissionId,
} from "@ekklesia/contracts";
import {
  AUTHORIZATION_GRANT_LIST_MAX_LIMIT,
  type AuthorizationStore,
  AuthorizationStoreError,
  CORE_AUTHORIZATION_GRANTS_MANAGE,
  type GrantPageBoundary,
  type GrantRecord,
} from "@ekklesia/core/authorization";
import { Hono } from "hono";
import type { Context } from "hono";
import {
  type AuthorizationMiddlewareOptions,
  getAuthorizedPrincipal,
  requirePermission,
  requireTrustedOrigin,
} from "./authorization-middleware.js";
import { CORE_MUTATION_MAX_BODY_BYTES, platformBodyLimit } from "./body-limits.js";

export interface CreateGrantsRoutesOptions extends AuthorizationMiddlewareOptions {
  readonly store: AuthorizationStore;
  readonly trustedOrigins: ReadonlySet<string>;
  /** Injected only so expiration validation is deterministic under test. Production composition
   * leaves this unset and the routes read real time. */
  readonly now?: () => Date;
}

const DEFAULT_LIST_LIMIT = 50;

function sanitizedStoreErrorResponse(c: Context, error: unknown): Response {
  c.header("Cache-Control", "no-store");
  if (error instanceof AuthorizationStoreError) {
    if (error.code === "AUTHORIZATION_GRANT_NOT_FOUND") {
      return c.json({ code: error.code }, 404);
    }
    // The one conflict the caller can act on. It deliberately reveals nothing about the grant that
    // already exists — not its id, actor, scope, source reference, or expiry — only that an
    // equivalent authorization is already effective for this subject.
    if (error.code === "AUTHORIZATION_GRANT_ALREADY_EXISTS") {
      return c.json({ code: error.code }, 409);
    }
    // Defense in depth: the routes below reject both of these before ever reaching the store, so
    // arriving here means a request-shaped problem slipped through. It is still a client input
    // failure, never an infrastructure one, and it reports exactly like any other malformed
    // request rather than leaking the store's internal distinction.
    if (
      error.code === "AUTHORIZATION_GRANT_EXPIRATION_INVALID" ||
      error.code === "AUTHORIZATION_GRANT_LIMIT_INVALID"
    ) {
      return c.json({ code: "INVALID_REQUEST" }, 400);
    }
    return c.json({ code: error.code }, 503);
  }
  return c.json({ code: "INTERNAL_ERROR" }, 503);
}

interface ParsedCreateGrantBody {
  readonly expiresAt?: Date;
  readonly permission: PermissionId;
  readonly subjectUserId: EkklesiaUserId;
}

const CREATE_GRANT_ALLOWED_KEYS = new Set(["subjectUserId", "permission", "expiresAt"]);

/**
 * The one accepted expiration representation: `YYYY-MM-DDTHH:mm:ss.sssZ`, byte-for-byte equal to
 * the parsed `Date`'s own `toISOString()`.
 *
 * `new Date(value)` alone was far too permissive. It silently *normalized* impossible dates
 * (`2026-02-31T00:00:00.000Z` became March 3rd) and accepted locale-shaped input
 * (`"March 5, 2027"`), date-only values, offsets, and missing milliseconds — so what an operator
 * typed and what the platform stored could differ without any error. The regular expression pins
 * the lexical form and the round-trip comparison rejects every value the parser would otherwise
 * quietly rewrite.
 */
const CANONICAL_INSTANT_PATTERN = /^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d{3}Z$/u;

function parseCanonicalFutureInstant(value: unknown, now: Date): Date | undefined {
  if (typeof value !== "string" || !CANONICAL_INSTANT_PATTERN.test(value)) {
    return undefined;
  }
  const parsed = new Date(value);
  if (Number.isNaN(parsed.getTime()) || parsed.toISOString() !== value) {
    return undefined;
  }
  // Strictly future: an expiration equal to or before the acceptance clock produces a grant that
  // is already dead, which is never what the caller meant.
  if (parsed.getTime() <= now.getTime()) {
    return undefined;
  }
  return parsed;
}

/**
 * Accepts only `subjectUserId`, `permission`, and an optional `expiresAt`. Any other key present —
 * `actor`, `sourceKind`, `sourceRef`, any audit field, `createdAt`, `revokedAt`, a grant id, or
 * anything claiming owner/effective-permission state — makes the whole body invalid rather than
 * being silently dropped, so a caller cannot smuggle server-derived fields through a request that
 * otherwise looks well-formed.
 *
 * **`scope` is deliberately among the rejected keys**, including when supplied as `null`, empty, or
 * an otherwise valid scope string. Core's scoped-grant semantics remain intact for trusted internal
 * callers, but no HTTP route middleware supplies a scope to the evaluator today, so a scope
 * accepted here would produce a grant that looks meaningful, persists, appears in listings, and can
 * authorize nothing at all. Accepting it would be offering a switch that is not connected to
 * anything. When a server-owned resolver exists, this is the one place that changes.
 */
function parseCreateGrantBody(raw: unknown, now: Date): ParsedCreateGrantBody | undefined {
  if (typeof raw !== "object" || raw === null || Array.isArray(raw)) {
    return undefined;
  }
  const body = raw as Record<string, unknown>;
  if (Object.keys(body).some((key) => !CREATE_GRANT_ALLOWED_KEYS.has(key))) {
    return undefined;
  }

  const subjectUserId = safeParseEkklesiaUserId(body.subjectUserId);
  if (!subjectUserId.success) {
    return undefined;
  }
  const permission = safeParsePermissionId(body.permission);
  if (!permission.success) {
    return undefined;
  }

  let expiresAt: Date | undefined;
  if (body.expiresAt !== undefined) {
    expiresAt = parseCanonicalFutureInstant(body.expiresAt, now);
    if (expiresAt === undefined) {
      return undefined;
    }
  }

  return Object.freeze({
    ...(expiresAt === undefined ? {} : { expiresAt }),
    permission: permission.data,
    subjectUserId: subjectUserId.data,
  });
}

const CURSOR_VERSION = 1;
const BASE64URL_PATTERN = /^[A-Za-z0-9_-]+$/u;

/**
 * An opaque pagination *position*, not an authorization token. It carries only the subject user id,
 * the boundary row's creation instant, and the boundary grant id — never a permission, scope,
 * source reference, actor, credential, or secret — so there is nothing in it worth protecting.
 *
 * It is deliberately unsigned. Signing would imply the cursor carries authority it does not have:
 * the permission check and the server-side subject filter remain authoritative on every page, and
 * a forged cursor can at most name a different position within grants the caller is already
 * entitled to list. The strict decode below still refuses anything that is not exactly what this
 * function would emit.
 */
function encodeCursor(userId: EkklesiaUserId, boundary: GrantPageBoundary): string {
  return Buffer.from(
    JSON.stringify({
      g: boundary.id,
      t: boundary.createdAt.toISOString(),
      u: userId,
      v: CURSOR_VERSION,
    }),
    "utf8",
  ).toString("base64url");
}

/**
 * Strict in every dimension: canonical unpadded base64url, valid UTF-8 JSON, an object with exactly
 * the four expected keys, the exact version, a subject matching the *requested* one, a canonical
 * `toISOString()` timestamp, a canonical `GrantId`, and — the catch-all — a re-encoding that
 * reproduces the supplied string byte-for-byte, which rejects padding, trailing data, and any
 * alternative encoding of the same payload. A rejected cursor reveals nothing it decoded.
 */
function decodeCursor(raw: string, userId: EkklesiaUserId): GrantPageBoundary | undefined {
  if (!BASE64URL_PATTERN.test(raw)) {
    return undefined;
  }
  let parsed: unknown;
  try {
    parsed = JSON.parse(Buffer.from(raw, "base64url").toString("utf8"));
  } catch {
    return undefined;
  }
  if (typeof parsed !== "object" || parsed === null || Array.isArray(parsed)) {
    return undefined;
  }
  const payload = parsed as Record<string, unknown>;
  if (Object.keys(payload).sort().join(",") !== "g,t,u,v") {
    return undefined;
  }
  if (payload.v !== CURSOR_VERSION || payload.u !== userId || typeof payload.t !== "string") {
    return undefined;
  }
  const createdAt = new Date(payload.t);
  if (Number.isNaN(createdAt.getTime()) || createdAt.toISOString() !== payload.t) {
    return undefined;
  }
  const id = safeParseGrantId(payload.g);
  if (!id.success) {
    return undefined;
  }
  const boundary: GrantPageBoundary = Object.freeze({ createdAt, id: id.data });
  if (encodeCursor(userId, boundary) !== raw) {
    return undefined;
  }
  return boundary;
}

const LIST_ALLOWED_QUERY_KEYS = new Set(["userId", "limit", "cursor"]);
/** Canonical base-10, no sign, no leading zero, no decimal point, no whitespace, no exponent. */
const CANONICAL_POSITIVE_INTEGER_PATTERN = /^[1-9][0-9]*$/u;

interface ParsedListQuery {
  readonly after?: GrantPageBoundary;
  readonly limit: number;
  readonly subjectUserId: EkklesiaUserId;
}

/** Fully validated before any store or database work happens, so an invalid page request never
 * becomes a query, and never becomes a way to probe which subjects or grants exist. */
function parseListQuery(url: string): ParsedListQuery | undefined {
  const searchParams = new URL(url).searchParams;
  for (const key of searchParams.keys()) {
    if (!LIST_ALLOWED_QUERY_KEYS.has(key) || searchParams.getAll(key).length > 1) {
      return undefined;
    }
  }

  const subjectUserId = safeParseEkklesiaUserId(searchParams.get("userId"));
  if (!subjectUserId.success) {
    return undefined;
  }

  let limit = DEFAULT_LIST_LIMIT;
  const rawLimit = searchParams.get("limit");
  if (rawLimit !== null) {
    if (!CANONICAL_POSITIVE_INTEGER_PATTERN.test(rawLimit)) {
      return undefined;
    }
    limit = Number(rawLimit);
    if (!Number.isSafeInteger(limit) || limit < 1 || limit > AUTHORIZATION_GRANT_LIST_MAX_LIMIT) {
      return undefined;
    }
  }

  let after: GrantPageBoundary | undefined;
  const rawCursor = searchParams.get("cursor");
  if (rawCursor !== null) {
    after = decodeCursor(rawCursor, subjectUserId.data);
    if (after === undefined) {
      return undefined;
    }
  }

  return Object.freeze({
    ...(after === undefined ? {} : { after }),
    limit,
    subjectUserId: subjectUserId.data,
  });
}

function serializeGrant(grant: GrantRecord) {
  return {
    createdAt: grant.createdAt.toISOString(),
    expiresAt: grant.expiresAt ? grant.expiresAt.toISOString() : null,
    id: grant.id,
    permission: grant.permission,
    revokedAt: grant.revokedAt ? grant.revokedAt.toISOString() : null,
    scope: grant.scope ?? null,
    sourceKind: grant.sourceKind,
    userId: grant.userId,
  };
}

/**
 * The v1 explicit-grant management API: list, create, and revoke *explicit* grants only. Every
 * route requires `core.authorization.grants.manage`; a platform owner passes through the
 * evaluator's existing owner bypass without ever needing an explicit grant of this permission
 * themselves — that bypass is exactly how a platform owner deliberately delegates grant
 * administration to another account by granting them this one permission.
 *
 * Relationship-derived grants are never reachable through this API in either direction: creation
 * always hard-codes `sourceKind: "explicit"` server-side (the request body cannot supply a
 * `sourceKind` at all), and revocation is constrained to `sourceKind: "explicit"`, so attempting
 * to revoke a relationship-derived grant by id behaves exactly like the grant does not exist —
 * those grants remain owned by the module operation that established the relationship.
 *
 * Creation is unscoped-only; see `parseCreateGrantBody`.
 */
export function createGrantsRoutes(options: CreateGrantsRoutesOptions): Hono {
  const routes = new Hono();
  const now = options.now ?? ((): Date => new Date());
  const requireManagePermission = requirePermission(options, CORE_AUTHORIZATION_GRANTS_MANAGE);
  const requireOrigin = requireTrustedOrigin(options.trustedOrigins);
  // Origin is checked first (a rejected cross-origin mutation must never have its body read), then
  // the body-size limit runs before permission evaluation, so an oversized mutation never reaches
  // authorization work or the store.
  const mutationBodyLimit = platformBodyLimit(CORE_MUTATION_MAX_BODY_BYTES);

  routes.get("/api/v1/grants", requireManagePermission, async (c) => {
    c.header("Cache-Control", "no-store");
    // Reached only after `requireManagePermission` allowed the caller, so query validation can
    // never disclose a validation distinction — or the existence of any subject or grant — to an
    // unauthorized caller.
    const query = parseListQuery(c.req.url);
    if (!query) {
      return c.json({ code: "INVALID_REQUEST" }, 400);
    }
    try {
      const page = await options.store.listGrantsForUser(query.subjectUserId, {
        ...(query.after === undefined ? {} : { after: query.after }),
        limit: query.limit,
        sourceKind: "explicit",
      });
      return c.json(
        {
          grants: page.grants.map(serializeGrant),
          nextCursor:
            page.nextBoundary === undefined
              ? null
              : encodeCursor(query.subjectUserId, page.nextBoundary),
        },
        200,
      );
    } catch (error) {
      return sanitizedStoreErrorResponse(c, error);
    }
  });

  routes.post(
    "/api/v1/grants",
    requireOrigin,
    mutationBodyLimit,
    requireManagePermission,
    async (c) => {
      c.header("Cache-Control", "no-store");
      const principal = getAuthorizedPrincipal(c);
      if (!isAuthenticatedPrincipal(principal)) {
        return c.json({ code: "AUTHORIZATION_DENIED" }, 403);
      }

      let rawBody: unknown;
      try {
        rawBody = await c.req.json();
      } catch {
        return c.json({ code: "INVALID_REQUEST" }, 400);
      }
      const parsed = parseCreateGrantBody(rawBody, now());
      if (!parsed) {
        return c.json({ code: "INVALID_REQUEST" }, 400);
      }

      // A well-formed PermissionId is not necessarily a *registered* one. Only the trusted registry
      // (never the request) decides what may be granted — the same registry `requireManagePermission`
      // already consults for the caller's own `core.authorization.grants.manage` check — so a caller
      // cannot pre-create a dormant grant for an invented identifier that later becomes effective the
      // moment someone registers it. Sanitized identically to any other denial: this must never reveal
      // whether the identifier was malformed (400, above) or simply unregistered (403, here).
      if (!options.registry.has(parsed.permission)) {
        return c.json({ code: "AUTHORIZATION_DENIED" }, 403);
      }

      try {
        const grant = await options.store.createGrant({
          actor: createUserActor(principal.userId),
          ...(parsed.expiresAt === undefined ? {} : { expiresAt: parsed.expiresAt }),
          permission: parsed.permission,
          sourceKind: "explicit",
          userId: parsed.subjectUserId,
        });
        return c.json({ grant: serializeGrant(grant) }, 201);
      } catch (error) {
        return sanitizedStoreErrorResponse(c, error);
      }
    },
  );

  routes.post(
    "/api/v1/grants/:grantId/revoke",
    requireOrigin,
    mutationBodyLimit,
    requireManagePermission,
    async (c) => {
      c.header("Cache-Control", "no-store");
      const principal = getAuthorizedPrincipal(c);
      if (!isAuthenticatedPrincipal(principal)) {
        return c.json({ code: "AUTHORIZATION_DENIED" }, 403);
      }

      // Canonical-UUID validation happens after authorization but strictly before any store or
      // database call: a malformed id previously reached PostgreSQL's own UUID comparison and came
      // back as an indistinguishable infrastructure failure (503) rather than a request problem.
      const grantId = safeParseGrantId(c.req.param("grantId"));
      if (!grantId.success) {
        return c.json({ code: "INVALID_REQUEST" }, 400);
      }

      try {
        await options.store.revokeGrant({
          actor: createUserActor(principal.userId),
          grantId: grantId.data satisfies GrantId,
          sourceKind: "explicit",
        });
        return c.json({ success: true }, 200);
      } catch (error) {
        return sanitizedStoreErrorResponse(c, error);
      }
    },
  );

  return routes;
}