/**
 * Every path the app answers, in one table. A route reads its request,
 * calls an action, and shapes the answer for its door — HTML for a
 * browser, JSON for a script — and that is all a route does.
 *
 * A route that is part of the API says so beside itself (`api`): one
 * sentence, and the shape of what it takes and gives, as JSON Schema.
 * `bun run contract:emit` writes those into `contract/openapi.json`, the
 * tests fail when the committed file and this table disagree, and
 * `GET /openapi.json` serves it. The shapes describe; the checks that hold
 * are still the actions' own.
 */

import type { Database } from "bun:sqlite";
import { existsSync, readFileSync } from "node:fs";
import {
  addNote,
  BODY_MAX,
  deleteNote,
  getAudit,
  getNote,
  listAudit,
  listNotes,
  updateNote,
  type Failure,
  type Result,
} from "./actions.ts";
import { commit, env, forgeUrl, startedAt, version } from "./env.ts";
import {
  back,
  fields,
  html,
  json,
  readForm,
  readJson,
  readNotice,
  SECURITY,
  staticFile,
  text,
} from "./http.ts";
import { events } from "./live.ts";
import { rpc } from "./mcp.ts";
import { home } from "./page.ts";
import { tokensCss } from "./tokens.ts";
import type { Who } from "./who.ts";

export interface Context {
  readonly request: Request;
  readonly url: URL;
  readonly db: Database;
  readonly who: Who;
  readonly params: Record<string, string>;
}

/** A JSON Schema, as plain data. */
export type Schema = Readonly<Record<string, unknown>>;

/** What an API route is, for the description: never consulted to decide anything. */
export interface Api {
  readonly summary: string;
  /** The body it reads. */
  readonly body?: Schema;
  /** What it answers when it succeeds, and with which status (200). */
  readonly answer: Schema;
  readonly status?: number;
  /** The query parameters it reads. */
  readonly query?: Readonly<Record<string, Schema>>;
}

export interface Route {
  readonly method: "GET" | "POST" | "PATCH" | "DELETE";
  readonly path: string;
  readonly handle: (ctx: Context) => Response | Promise<Response>;
  readonly api?: Api;
}

// The shapes the API speaks in, named once.
export const NOTE: Schema = {
  type: "object",
  properties: {
    id: { type: "integer" },
    body: { type: "string", minLength: 1, maxLength: BODY_MAX },
    author_id: { type: "string" },
    author_name: { type: "string" },
    created_at: { type: "string", format: "date-time" },
    updated_at: { type: "string", format: "date-time" },
  },
  required: [
    "id",
    "body",
    "author_id",
    "author_name",
    "created_at",
    "updated_at",
  ],
};
const NOTE_BODY: Schema = {
  type: "object",
  properties: { body: { type: "string", minLength: 1, maxLength: BODY_MAX } },
  required: ["body"],
};
export const AUDIT_ROW: Schema = {
  type: "object",
  properties: {
    id: { type: "integer" },
    at: { type: "string", format: "date-time" },
    who_id: { type: ["string", "null"] },
    who_name: { type: ["string", "null"] },
    role: { enum: ["anon", "user", "admin"] },
    resource: { type: "string" },
    verb: { type: "string" },
    target: { type: ["string", "null"] },
    allowed: { enum: [0, 1] },
    outcome: { type: "string" },
  },
  required: ["id", "at", "role", "resource", "verb", "allowed", "outcome"],
};
export const ERROR: Schema = {
  type: "object",
  properties: { error: { type: "string" }, message: { type: "string" } },
  required: ["error"],
};
const LIMIT: Schema = {
  type: "integer",
  minimum: 1,
  maximum: 500,
  default: 100,
};
const list = (items: Schema): Schema => ({ type: "array", items });

const STATUS: Record<Failure, number> = {
  signin_required: 401,
  forbidden: 403,
  not_found: 404,
  invalid: 422,
};

/** A result as JSON: the value, or `{ error, message }` with the matching status. */
const answer = <T>(result: Result<T>, status = 200): Response =>
  result.ok
    ? json(result.value, status)
    : json(
        { error: result.error, message: result.message },
        STATUS[result.error],
      );

/** A result for a form: back to the page, with what went wrong if it did. */
const done = <T>(result: Result<T>): Response =>
  result.ok ? back() : back(result.message);

/** A whole number from the query, or undefined. */
const whole = (value: string | null): number | undefined =>
  value !== null && /^\d+$/.test(value) ? Number(value) : undefined;

// The API's description, read from git once: what the tests hold equal to this table.
const OPENAPI = new URL("../contract/openapi.json", import.meta.url);
const openapi = existsSync(OPENAPI) ? readFileSync(OPENAPI, "utf8") : undefined;

export const routes: readonly Route[] = [
  // The page. Forms post and come back; the list stays live over /events.
  {
    method: "GET",
    path: "/",
    handle: (c) => {
      const { notice, clear } = readNotice(c.request);
      const notes = listNotes(c.db, c.who);
      return html(
        home({ who: c.who, notes: notes.ok ? notes.value : [], notice }),
        200,
        clear,
      );
    },
  },
  {
    method: "POST",
    path: "/notes",
    handle: async (c) => {
      const form = await readForm(c.request);
      if (form === undefined) return text("too large", 413);
      return done(
        addNote(c.db, c.who, { body: String(form.get("body") ?? "") }),
      );
    },
  },
  {
    method: "POST",
    path: "/notes/:id/delete",
    handle: (c) => done(deleteNote(c.db, c.who, { id: Number(c.params.id) })),
  },

  // The JSON API: the same actions, the same identity, plain status codes.
  {
    method: "GET",
    path: "/api/notes",
    handle: (c) =>
      answer(
        listNotes(c.db, c.who, {
          limit: Number(c.url.searchParams.get("limit") ?? 100),
        }),
      ),
    api: {
      summary: "The notes, newest first.",
      query: { limit: LIMIT },
      answer: list(NOTE),
    },
  },
  {
    method: "POST",
    path: "/api/notes",
    handle: async (c) => {
      const body = await readJson(c.request);
      if (body === undefined) return json({ error: "too_large" }, 413);
      return answer(
        addNote(c.db, c.who, { body: String(fields(body).body ?? "") }),
        201,
      );
    },
    api: {
      summary: "Add a note as the person asking.",
      body: NOTE_BODY,
      answer: NOTE,
      status: 201,
    },
  },
  {
    method: "GET",
    path: "/api/notes/:id",
    handle: (c) => answer(getNote(c.db, c.who, { id: Number(c.params.id) })),
    api: { summary: "One note.", answer: NOTE },
  },
  {
    method: "PATCH",
    path: "/api/notes/:id",
    handle: async (c) => {
      const body = await readJson(c.request);
      if (body === undefined) return json({ error: "too_large" }, 413);
      return answer(
        updateNote(c.db, c.who, {
          id: Number(c.params.id),
          body: String(fields(body).body ?? ""),
        }),
      );
    },
    api: { summary: "Change a note's words.", body: NOTE_BODY, answer: NOTE },
  },
  {
    method: "DELETE",
    path: "/api/notes/:id",
    handle: (c) => answer(deleteNote(c.db, c.who, { id: Number(c.params.id) })),
    api: {
      summary: "Remove a note.",
      answer: {
        type: "object",
        properties: { id: { type: "integer" } },
        required: ["id"],
      },
    },
  },

  // Who tried to change what: the audit trail, for whoever the table lets read it.
  {
    method: "GET",
    path: "/api/audit",
    handle: (c) =>
      answer(
        listAudit(c.db, c.who, {
          limit: whole(c.url.searchParams.get("limit")) ?? 100,
          ...(whole(c.url.searchParams.get("before")) === undefined
            ? {}
            : { before: whole(c.url.searchParams.get("before"))! }),
        }),
      ),
    api: {
      summary: "The audit trail, newest first; `before` pages back by id.",
      query: { limit: LIMIT, before: { type: "integer" } },
      answer: list(AUDIT_ROW),
    },
  },
  {
    method: "GET",
    path: "/api/audit/:id",
    handle: (c) => answer(getAudit(c.db, c.who, { id: Number(c.params.id) })),
    api: { summary: "One row of the audit trail.", answer: AUDIT_ROW },
  },

  // Live events, and the MCP server (the tools are the actions too).
  { method: "GET", path: "/events", handle: (c) => events(c.request) },
  {
    method: "POST",
    path: "/mcp",
    handle: async (c) => {
      const message = await readJson(c.request);
      if (message === undefined) return json({ error: "too_large" }, 413);
      if (message === null)
        return json({
          jsonrpc: "2.0",
          id: null,
          error: { code: -32700, message: "parse error" },
        });
      const { status, body } = rpc(c.db, c.who, message);
      return body === undefined
        ? new Response(null, { status })
        : json(body, status);
    },
    api: {
      summary:
        "One JSON-RPC 2.0 message to the MCP server; its tools are the actions.",
      body: {
        type: "object",
        properties: {
          jsonrpc: { const: "2.0" },
          id: {},
          method: { type: "string" },
          params: { type: "object" },
        },
        required: ["jsonrpc", "method"],
      },
      answer: { type: "object" },
    },
  },
  {
    method: "GET",
    path: "/mcp",
    handle: () => text("this endpoint speaks JSON-RPC over POST", 405),
  },

  // Up or not, for the forge and for anyone watching: a separate path from
  // the page, so a health check never renders it.
  {
    method: "GET",
    path: "/healthz",
    handle: (c) => {
      let ok = true;
      try {
        c.db.query("SELECT 1").get();
      } catch {
        ok = false;
      }
      const uptime = Math.floor((Date.now() - startedAt) / 1000);
      return new Response(
        JSON.stringify({ ok, version, commit, env, uptime }),
        {
          status: ok ? 200 : 503,
          headers: {
            "content-type": "application/json; charset=utf-8",
            "cache-control": "no-store",
            ...SECURITY,
          },
        },
      );
    },
    api: {
      summary:
        "Whether the app is up: its version, commit, environment and seconds since it started.",
      answer: {
        type: "object",
        properties: {
          ok: { type: "boolean" },
          version: { type: "string" },
          commit: { type: "string" },
          env: { type: "string" },
          uptime: { type: "integer" },
        },
        required: ["ok", "version", "uptime"],
      },
    },
  },
  {
    method: "GET",
    path: "/openapi.json",
    handle: () =>
      openapi === undefined
        ? text("not found", 404)
        : new Response(openapi, {
            headers: {
              "content-type": "application/json; charset=utf-8",
              "cache-control": "no-cache",
              ...SECURITY,
            },
          }),
  },

  // The look: design/tokens.json, compiled at boot, cached for a year when linked by content.
  {
    method: "GET",
    path: "/tokens.css",
    handle: (c) =>
      new Response(tokensCss, {
        headers: {
          "content-type": "text/css; charset=utf-8",
          "cache-control": c.url.searchParams.has("v")
            ? "public, max-age=31536000, immutable"
            : "no-cache",
          ...SECURITY,
        },
      }),
  },

  // What the web expects of a site. Crawlers read the page, not the API;
  // a preview is a draft and is read by nobody. Where to report a
  // vulnerability is the forge's to say: it runs this app.
  {
    method: "GET",
    path: "/robots.txt",
    handle: () =>
      text(
        env === "production"
          ? "User-agent: *\nDisallow: /api/\nDisallow: /mcp\nDisallow: /events\nDisallow: /__forge/\n"
          : "User-agent: *\nDisallow: /\n",
      ),
  },
  {
    method: "GET",
    path: "/.well-known/security.txt",
    handle: () =>
      forgeUrl === undefined
        ? text("not found", 404)
        : new Response(null, {
            status: 302,
            headers: {
              location: new URL(
                "/.well-known/security.txt",
                forgeUrl,
              ).toString(),
              ...SECURITY,
            },
          }),
  },

  // Files under ./static, cached for a year when linked by content (`asset`).
  {
    method: "GET",
    path: "/static/:file",
    handle: (c) => staticFile(c.params.file ?? "", c.url.searchParams.has("v")),
  },
];

/** The route for a method and path, with what its `:names` matched. */
export function match(
  method: string,
  pathname: string,
): { route: Route; params: Record<string, string> } | undefined {
  const parts = pathname.split("/");
  for (const route of routes) {
    if (route.method !== method) continue;
    const pattern = route.path.split("/");
    if (pattern.length !== parts.length) continue;
    const params: Record<string, string> = {};
    const hit = pattern.every((p, i) => {
      if (p.startsWith(":")) {
        // A malformed escape is no match, never a thrown error.
        try {
          params[p.slice(1)] = decodeURIComponent(parts[i] ?? "");
          return true;
        } catch {
          return false;
        }
      }
      return p === parts[i];
    });
    if (hit) return { route, params };
  }
  return undefined;
}