import { z } from "zod";
import type { EkklesiaPrincipal } from "./identity.js";
import { type ModuleId, type PermissionId, permissionIdSchema } from "./identifiers.js";
import type { ModuleRuntimeServices } from "./module-database.js";

// Not imported from `./module-runtime.js`'s own `Awaitable` (structurally identical) — importing
// it would create a source dependency cycle with that module, which also imports from this one for
// `ModuleHttpRouteRegistrar`. `scripts/check-boundaries.ts` rejects any source cycle, including one
// formed only by `import type`, so this tiny, fixed-shape utility type is kept private here instead.
type Awaitable<Value> = Value | PromiseLike<Value>;

/** The exact, canonical HTTP methods a module route may declare. Uppercase only — a module never
 * gets `OPTIONS` (the platform owns CORS preflight) or a wildcard/all-methods registration. */
export const MODULE_HTTP_METHODS = ["DELETE", "GET", "PATCH", "POST", "PUT"] as const;

export type ModuleHttpMethod = (typeof MODULE_HTTP_METHODS)[number];

const moduleHttpMethods: ReadonlySet<string> = new Set(MODULE_HTTP_METHODS);

export function isModuleHttpMethod(value: unknown): value is ModuleHttpMethod {
  return typeof value === "string" && moduleHttpMethods.has(value);
}

/**
 * The platform-owned hard ceiling on any single module route's declared request-body allowance, in
 * bytes. No module route may declare a `maxBodyBytes` above this value — validated at registration
 * (`safeParseModuleRouteDefinition`, below), not merely documented. This is a security contract,
 * not a manifest capability: it does not gate on `manifestVersion` and is enforced identically for
 * every installed module regardless of its declared compatibility range. Large media transfer
 * belongs to a future dedicated storage design, never to widening this ceiling.
 */
export const MODULE_ROUTE_MAX_BODY_BYTES_CEILING = 1_048_576;

const moduleRouteMaxBodyBytesSchema = z
  .number()
  .int()
  .finite()
  .min(0)
  .max(MODULE_ROUTE_MAX_BODY_BYTES_CEILING);

const MODULE_ROUTE_PATH_MAX_LENGTH = 256;
const staticSegmentPattern = /^[a-z0-9]+(?:-[a-z0-9]+)*$/u;
const parameterSegmentPattern = /^:[a-z][a-zA-Z0-9]*$/u;

/**
 * A module-local route path — never the production-mounted `/api/v1/modules/<module-id>` path a
 * caller actually sends (`apps/api/src/module-http-routes.ts` owns that mapping). Not branded
 * (unlike `PermissionId`): like `PackageRelativePath`,
 * this is a validated location, not an opaque cross-system identifier. `"/"` is the module root;
 * any other canonical path begins with `/`, never ends with `/`, and is composed only of lowercase
 * kebab-case static segments or single `:parameterName` segments — no empty or repeated slashes, no
 * query string or fragment, no backslash or percent-encoding, no dot segments, and no wildcard or
 * catch-all segment, since none of those can ever match either segment grammar. Malformed input is
 * rejected outright rather than normalized, so a module can never register a path Core silently
 * reinterpreted.
 */
export const moduleRoutePathSchema = z
  .string()
  .max(MODULE_ROUTE_PATH_MAX_LENGTH)
  .superRefine((value, context) => {
    if (
      !value.startsWith("/") ||
      value.includes("\\") ||
      value.includes("%") ||
      value.includes("?") ||
      value.includes("#")
    ) {
      context.addIssue({
        code: "custom",
        message:
          "Module route paths must begin with / and must not contain backslashes, " +
          "percent-encoding, query strings, or fragments.",
      });
      return;
    }
    if (value === "/") {
      return;
    }
    if (value.endsWith("/")) {
      context.addIssue({
        code: "custom",
        message: "Non-root module route paths must not end with /.",
      });
      return;
    }

    const segments = value.slice(1).split("/");
    const parameterNames = new Set<string>();
    for (const segment of segments) {
      const isParameter = segment.startsWith(":");
      const matchesGrammar = isParameter
        ? parameterSegmentPattern.test(segment)
        : staticSegmentPattern.test(segment);
      if (!matchesGrammar) {
        context.addIssue({
          code: "custom",
          message:
            "Module route path segments must be lowercase kebab-case static segments or a " +
            "single :parameterName segment.",
        });
        return;
      }
      if (isParameter) {
        const parameterName = segment.slice(1);
        if (parameterNames.has(parameterName)) {
          context.addIssue({
            code: "custom",
            message: "Module route path parameter names must be unique within the path.",
          });
          return;
        }
        parameterNames.add(parameterName);
      }
    }
  });

export type ModuleRoutePath = z.output<typeof moduleRoutePathSchema>;

export function parseModuleRoutePath(input: unknown): ModuleRoutePath {
  return moduleRoutePathSchema.parse(input);
}

export function safeParseModuleRoutePath(input: unknown): z.ZodSafeParseResult<ModuleRoutePath> {
  return moduleRoutePathSchema.safeParse(input);
}

/**
 * Produces a deterministic key identifying a route's shape — method plus path with every parameter
 * segment collapsed to one placeholder — so `/events/:eventId` and `/events/:id` collide under the
 * same method exactly like the identical route they are, regardless of the parameter's chosen name.
 * Takes an already-validated `ModuleRoutePath`; never re-validates or echoes the original path.
 */
export function moduleRouteShapeKey(method: ModuleHttpMethod, path: ModuleRoutePath): string {
  if (path === "/") {
    return `${method} /`;
  }
  const shapeSegments = path
    .slice(1)
    .split("/")
    .map((segment) => (segment.startsWith(":") ? ":param" : segment));
  return `${method} /${shapeSegments.join("/")}`;
}

/** `"/"` is the module root and has no segments; every other canonical path is its `/`-separated
 * segments. Takes an already-validated `ModuleRoutePath`. */
function moduleRoutePathSegments(path: ModuleRoutePath): readonly string[] {
  return path === "/" ? [] : path.slice(1).split("/");
}

/**
 * Whether two routes of the same module can both match at least one request path.
 *
 * Two routes overlap when they share an HTTP method and a segment count, and at every position
 * either both segments are the same static literal or at least one is a parameter. Under this
 * route grammar — static kebab-case literals or `:name` parameters, with no wildcard, regex,
 * optional, or catch-all segment — that condition is exactly "some concrete path matches both".
 *
 * This exists because an overlap is a *permission* ambiguity, not a routing preference:
 * `GET /events/:id` and `GET /events/new` can carry different permissions, and with an
 * order-sensitive matcher whichever registered first decides which permission governs
 * `/events/new`. Core rejects the overlap at registration instead of picking a winner, so no
 * router's matching order can ever select the governing permission. Identical shapes (including
 * paths differing only in parameter name) remain the pre-existing duplicate result; callers check
 * that first.
 *
 * Deliberately framework-neutral: path semantics already live in this package, and nothing about
 * this rule may depend on Hono, which stays confined to `apps/api`.
 */
export function moduleRoutesOverlap(
  first: { readonly method: ModuleHttpMethod; readonly path: ModuleRoutePath },
  second: { readonly method: ModuleHttpMethod; readonly path: ModuleRoutePath },
): boolean {
  if (first.method !== second.method) {
    return false;
  }
  const firstSegments = moduleRoutePathSegments(first.path);
  const secondSegments = moduleRoutePathSegments(second.path);
  if (firstSegments.length !== secondSegments.length) {
    return false;
  }
  return firstSegments.every((segment, index) => {
    const other = secondSegments[index] as string;
    return segment.startsWith(":") || other.startsWith(":") || segment === other;
  });
}

/**
 * What a module's route handler receives about the caller, the match, and the platform services
 * available to it — never an authorization-store, grant-management, storage, jobs, configuration,
 * secrets, the Hono `Context`, or a raw Better Auth session. `principal` is already authorized by
 * the time a handler runs: `apps/api/src/module-http-routes.ts` mounts and enforces every route
 * before ever invoking its handler; this contracts-layer module never invokes a handler itself.
 * `services` is the same frozen `ModuleRuntimeServices` object the owning module's `start`/`stop`
 * hooks receive for this API runtime — never a fresh one built per request.
 *
 * ## `params` values are untrusted input
 *
 * `params` holds the HTTP router's **decoded** path values, frozen alongside this context. Decoding
 * is not validation, and the declaration grammar above constrains only what a module may *declare*
 * — it says nothing about what a request may *send*. A caller can percent-encode anything into a
 * single segment, so a decoded value routinely contains characters no declared path could:
 * verified against the pinned router, `%2F..%2Fadmin` arrives as `/../admin`, `a%5Cb` as `a\b`,
 * `a%00b` with an embedded NUL, `a%0D%0Ab` with CR/LF, and `%C3%A9v%C3%A9nement` as `événement`.
 *
 * Every handler must therefore validate each parameter it uses against its own exact domain
 * grammar — a UUID, slug, date, numeric id, or whatever that module owns — **before** any
 * database, filesystem, command, identifier, or other side-effecting use, and reject a missing,
 * repeated, malformed, or semantically invalid value with its own sanitized response. Re-encoding,
 * decode/re-encode round-tripping, or inspecting the raw URL is not a substitute for that check.
 * The platform deliberately supplies no generic parameter grammar: module parameters are
 * module-owned domain types, and one platform-wide pattern would either reject legitimate values
 * or approve meaningless ones.
 *
 * The platform continues to own authentication, authorization, `Origin`, CORS, body limits, cache
 * behavior, and uncaught-handler sanitization; permission enforcement always completes before a
 * handler — and therefore any parameter validation it performs — can run.
 */
export interface ModuleRouteHandlerContext {
  readonly moduleId: ModuleId;
  readonly principal: EkklesiaPrincipal;
  readonly params: Readonly<Record<string, string>>;
  readonly services: ModuleRuntimeServices;
}

/** A framework-neutral Fetch handler: standard `Request` in, standard `Response` out. The full
 * query string remains available through `Request.url`; there is no competing query or body
 * abstraction. */
export type ModuleRouteHandler = (
  request: Request,
  context: ModuleRouteHandlerContext,
) => Awaitable<Response>;

/**
 * What a module passes to `http.route(...)` during `register`. `permission` is a plain string here
 * (never the branded `PermissionId`) so a module can write a literal permission id without an
 * explicit parse call first; `http.route` validates and brands it. `maxBodyBytes` is the route's
 * conscious request-body contract — `0` means the route accepts no body at all (a non-empty
 * declared or streamed body is rejected), and any other value is the exact maximum number of bytes
 * accepted, capped at `MODULE_ROUTE_MAX_BODY_BYTES_CEILING`. This is a security contract the
 * platform enforces before a handler ever runs, not a manifest capability: it is not optional and
 * has no implicit default, so a module author must make an explicit choice for every route. The
 * type has exactly these five fields — a module cannot specify a baseline, mount prefix, absolute
 * path, CORS/origin policy, authentication behavior, grant/platform-owner state, middleware, audit
 * metadata, another module's namespace, or an unprotected/no-permission route.
 */
export interface ModuleRouteDefinitionInput {
  readonly method: ModuleHttpMethod;
  readonly path: string;
  readonly permission: string;
  readonly maxBodyBytes: number;
  readonly handler: ModuleRouteHandler;
}

/** The validated, canonical form of a `ModuleRouteDefinitionInput` — what `http.route` produces
 * only after every field passes its own grammar. */
export interface ModuleRouteDefinition {
  readonly method: ModuleHttpMethod;
  readonly path: ModuleRoutePath;
  readonly permission: PermissionId;
  readonly maxBodyBytes: number;
  readonly handler: ModuleRouteHandler;
}

/** The Fetch-based registrar exposed as `context.http` during `register` only — never on
 * `ModuleRuntimeContext`, so `start`/`stop` cannot register a route after the fact. */
export interface ModuleHttpRouteRegistrar {
  route(definition: ModuleRouteDefinitionInput): void;
}

/** One published route in `StartedModuleRuntime`'s immutable route snapshot — the same validated
 * fields as `ModuleRouteDefinition` plus the owning module's ID, which the production mount prefix
 * (`/api/v1/modules/<module-id>`, `apps/api/src/module-http-routes.ts`) uses to keep two modules'
 * routes from ever colliding regardless of their own local paths. */
export interface RegisteredModuleHttpRoute {
  readonly moduleId: ModuleId;
  readonly method: ModuleHttpMethod;
  readonly path: ModuleRoutePath;
  readonly permission: PermissionId;
  readonly maxBodyBytes: number;
  readonly handler: ModuleRouteHandler;
}

const moduleRouteDefinitionKeys = new Set([
  "method",
  "path",
  "permission",
  "maxBodyBytes",
  "handler",
]);

function isRecord(value: unknown): value is Record<string, unknown> {
  return typeof value === "object" && value !== null && !Array.isArray(value);
}

function hasModuleRouteDefinitionShape(value: unknown): value is {
  method: unknown;
  path: unknown;
  permission: unknown;
  maxBodyBytes: unknown;
  handler: unknown;
} {
  if (!isRecord(value)) {
    return false;
  }
  const keys = Object.keys(value);
  return (
    keys.length === moduleRouteDefinitionKeys.size &&
    keys.every((key) => moduleRouteDefinitionKeys.has(key)) &&
    typeof value.handler === "function"
  );
}

export type ModuleRouteDefinitionIssueCode =
  | "MODULE_ROUTE_DEFINITION_INVALID"
  | "MODULE_ROUTE_METHOD_INVALID"
  | "MODULE_ROUTE_PATH_INVALID"
  | "MODULE_ROUTE_PERMISSION_INVALID"
  | "MODULE_ROUTE_MAX_BODY_BYTES_INVALID";

export type ModuleRouteDefinitionParseResult =
  | { readonly success: true; readonly data: ModuleRouteDefinition }
  | { readonly success: false; readonly code: ModuleRouteDefinitionIssueCode };

/**
 * Validates every field-level rule a route definition must satisfy on its own — exact shape,
 * canonical method, canonical path, well-formed permission id, well-formed body-size contract — but
 * never whether the permission is actually declared by the registering module. That ownership check
 * needs the module's own manifest and belongs to the caller (Core's module runtime), not this
 * framework-neutral contract. Never echoes the rejected input in the returned code.
 */
export function safeParseModuleRouteDefinition(value: unknown): ModuleRouteDefinitionParseResult {
  if (!hasModuleRouteDefinitionShape(value)) {
    return { success: false, code: "MODULE_ROUTE_DEFINITION_INVALID" };
  }
  if (!isModuleHttpMethod(value.method)) {
    return { success: false, code: "MODULE_ROUTE_METHOD_INVALID" };
  }
  const parsedPath = moduleRoutePathSchema.safeParse(value.path);
  if (!parsedPath.success) {
    return { success: false, code: "MODULE_ROUTE_PATH_INVALID" };
  }
  const parsedPermission = permissionIdSchema.safeParse(value.permission);
  if (!parsedPermission.success) {
    return { success: false, code: "MODULE_ROUTE_PERMISSION_INVALID" };
  }
  const parsedMaxBodyBytes = moduleRouteMaxBodyBytesSchema.safeParse(value.maxBodyBytes);
  if (!parsedMaxBodyBytes.success) {
    return { success: false, code: "MODULE_ROUTE_MAX_BODY_BYTES_INVALID" };
  }
  return {
    success: true,
    data: Object.freeze({
      method: value.method,
      path: parsedPath.data,
      permission: parsedPermission.data,
      maxBodyBytes: parsedMaxBodyBytes.data,
      handler: value.handler as ModuleRouteHandler,
    }),
  };
}

export function parseModuleRouteDefinition(value: unknown): ModuleRouteDefinition {
  const result = safeParseModuleRouteDefinition(value);
  if (!result.success) {
    throw new TypeError("Invalid Ekklesia module route definition.");
  }
  return result.data;
}