/**
 * An MCP server over plain HTTP: `POST /mcp` takes one JSON-RPC 2.0
 * message and answers with JSON (streamable HTTP without the stream —
 * nothing here needs to push). The tools are the actions, called with the
 * same identity the page gets, so an agent speaking MCP through the forge
 * is the person whose grant it carries, and a bare one is anonymous.
 */

import type { Database } from "bun:sqlite";
import {
  addNote,
  BODY_MAX,
  deleteNote,
  findNote,
  getNote,
  listNotes,
  openOrCreate,
  searchNotes,
  today,
  updateNote,
  type Result,
} from "./actions.ts";
import { title } from "./env.ts";
import { fields } from "./http.ts";
import type { Who } from "./who.ts";

interface Tool {
  readonly name: string;
  readonly description: string;
  readonly inputSchema: Record<string, unknown>;
  readonly run: (
    db: Database,
    who: Who,
    args: Record<string, unknown>,
  ) => Result<unknown>;
}

const str = (v: unknown): string | undefined => (typeof v === "string" ? v : undefined);

/** A note by `id`, or by `title` in the caller's vault. */
const which = (db: Database, who: Who, args: Record<string, unknown>) =>
  args.id !== undefined
    ? getNote(db, who, { id: Number(args.id) })
    : findNote(db, who, { title: str(args.title) ?? "" });

const NOTE_REF = {
  id: { type: "integer", description: "The note's id." },
  title: { type: "string", description: "Or its title (any case)." },
};

export const tools: readonly Tool[] = [
  {
    name: "list_notes",
    description:
      "The titles in your vault (id, title, pinned, updated_at), pinned first then most recently changed. Read one with read_note.",
    inputSchema: {
      type: "object",
      properties: {
        limit: { type: "integer", minimum: 1, maximum: 5000, description: "At most this many." },
      },
    },
    run: (db, who, args) => {
      const listed = listNotes(db, who, args.limit === undefined ? {} : { limit: Number(args.limit) });
      return listed.ok
        ? {
            ok: true,
            value: listed.value.map(({ id, title, pinned, updated_at }) => ({ id, title, pinned: pinned === 1, updated_at })),
          }
        : listed;
    },
  },
  {
    name: "search_notes",
    description:
      'Search your vault: every word must appear; "a phrase" matches whole; #tag (or tag:name) must be on the note. Title matches rank first.',
    inputSchema: {
      type: "object",
      properties: { q: { type: "string", maxLength: 500 }, limit: { type: "integer", minimum: 1, maximum: 500 } },
      required: ["q"],
    },
    run: (db, who, args) =>
      searchNotes(db, who, { q: str(args.q) ?? "", ...(args.limit === undefined ? {} : { limit: Number(args.limit) }) }),
  },
  {
    name: "read_note",
    description: "One note's markdown, by id or title.",
    inputSchema: { type: "object", properties: NOTE_REF },
    run: (db, who, args) => which(db, who, args),
  },
  {
    name: "create_note",
    description:
      "Write a new note in markdown. Link other notes with [[Their title]] and tag with #tags. Titles are unique in the vault.",
    inputSchema: {
      type: "object",
      properties: {
        title: { type: "string", maxLength: 200 },
        body: { type: "string", maxLength: BODY_MAX },
      },
      required: ["title"],
    },
    run: (db, who, args) =>
      addNote(db, who, { title: str(args.title) ?? "", body: str(args.body) ?? "" }),
  },
  {
    name: "update_note",
    description:
      "Replace a note's body, rename it (links to it follow), or pin it. Give only what changes.",
    inputSchema: {
      type: "object",
      properties: {
        id: { type: "integer" },
        title: { type: "string", maxLength: 200 },
        body: { type: "string", maxLength: BODY_MAX },
        pinned: { type: "boolean" },
      },
      required: ["id"],
    },
    run: (db, who, args) =>
      updateNote(db, who, {
        id: Number(args.id),
        ...(str(args.title) === undefined ? {} : { title: str(args.title)! }),
        ...(str(args.body) === undefined ? {} : { body: str(args.body)! }),
        ...(typeof args.pinned === "boolean" ? { pinned: args.pinned } : {}),
      }),
  },
  {
    name: "append_to_note",
    description:
      "Add text to the end of a note, made if it does not exist yet. With no title, today's daily note (YYYY-MM-DD, UTC).",
    inputSchema: {
      type: "object",
      properties: {
        title: { type: "string", maxLength: 200 },
        text: { type: "string", maxLength: BODY_MAX },
      },
      required: ["text"],
    },
    run: (db, who, args) => {
      const day = today();
      const name = str(args.title) ?? day;
      const opened = openOrCreate(db, who, { title: name, body: name === day ? `# ${day}\n` : "" });
      if (!opened.ok) return opened;
      const body = opened.value.body.replace(/\s*$/, "");
      return updateNote(db, who, {
        id: opened.value.id,
        body: `${body}${body === "" ? "" : "\n\n"}${str(args.text) ?? ""}\n`,
      });
    },
  },
  {
    name: "delete_note",
    description: "Remove a note by id. This cannot be undone.",
    inputSchema: {
      type: "object",
      properties: { id: { type: "integer" } },
      required: ["id"],
    },
    run: (db, who, args) => deleteNote(db, who, { id: Number(args.id) }),
  },
];

/** One JSON-RPC message in, an HTTP status and a body out (a notification gets 202 and no body). */
export function rpc(
  db: Database,
  who: Who,
  message: unknown,
): { status: number; body?: unknown } {
  const m = fields(message);
  const id = m.id ?? null;
  const reply = (result: unknown) => ({
    status: 200,
    body: { jsonrpc: "2.0", id, result },
  });
  const refuse = (code: number, text: string) => ({
    status: 200,
    body: { jsonrpc: "2.0", id, error: { code, message: text } },
  });
  if (m.jsonrpc !== "2.0" || typeof m.method !== "string")
    return refuse(-32600, "not a JSON-RPC 2.0 request");
  if (m.id === undefined) return { status: 202 };
  const params = fields(m.params);
  switch (m.method) {
    case "initialize":
      return reply({
        protocolVersion: "2025-06-18",
        capabilities: { tools: {} },
        serverInfo: { name: title, version: "1" },
      });
    case "ping":
      return reply({});
    case "tools/list":
      return reply({
        tools: tools.map(({ name, description, inputSchema }) => ({
          name,
          description,
          inputSchema,
        })),
      });
    case "tools/call": {
      const tool = tools.find((t) => t.name === params.name);
      if (tool === undefined)
        return refuse(-32602, `no tool named ${String(params.name)}`);
      const result = tool.run(db, who, fields(params.arguments));
      return reply(
        result.ok
          ? { content: [{ type: "text", text: JSON.stringify(result.value) }] }
          : {
              content: [
                { type: "text", text: `${result.error}: ${result.message}` },
              ],
              isError: true,
            },
      );
    }
    default:
      return refuse(-32601, `no method ${m.method}`);
  }
}