import { content } from "@deadhead/content";
import {
  routes,
  type RouteName,
  type RouteRequest,
  type RouteResponse,
  type SaveDocument,
  type SaveParse,
} from "@deadhead/schema";
import { realToGame, type RealTime } from "@deadhead/sim";
import type { z } from "zod";
import { EngineCore, type CoreDeps, type RandomSource } from "../core";
import type { NotificationSync } from "../notifications";
import { decodeSave, encodeSave } from "../save-code";
import { commandTable } from "./commands";
import { startingSave } from "./company";
import { CommandError, fail } from "./errors";
import { pruneSave, resolveArrivals } from "./resolve";
import { playerState } from "./state";

/** The commands the engine runs: the whole route catalog (CR-014). */
export type CommandName = RouteName;
export const DEV_COMMANDS: readonly CommandName[] = [
  "devAdvanceClock",
  "devAddCredits",
  "devPilot",
  "devShip",
  "devDiscoverAll",
];

/** What a command gets: a copy of the save (with due arrivals already applied). */
export interface CommandContext {
  save: SaveDocument;
  now: RealTime;
  random: RandomSource;
}

export type CommandHandler<N extends CommandName> = (
  ctx: CommandContext,
  input: z.output<(typeof routes)[N]["request"]>,
) => RouteResponse<N>;

/** Commands that run before a company exists, or touch the clock rather than the save. */
type SpecialCommand =
  "getServerTime" | "createGuest" | "newCompany" | "devAdvanceClock" | "exportSave" | "importSave";
export type CommandTable = { [N in Exclude<CommandName, SpecialCommand>]: CommandHandler<N> };

export interface GameEngineOptions extends CoreDeps {
  clock: CoreDeps["clock"] & { advance?(ms: number): void; offsetMs?: number };
  /** Developer commands (non-production builds only, CR-011). */
  devTools?: boolean;
  /** Check every response against its schema (tests and development). Default true. */
  validateResponses?: boolean;
  /** Replaces command handlers (tests only). */
  overrides?: Partial<CommandTable>;
  /** Local notifications (decision 0.5.91); none if absent. */
  notifications?: NotificationSync;
  /** Migrates and validates an imported save (tests replace it). Default: the schema's `migrateSave`. */
  migrate?: (raw: unknown) => SaveParse;
}

function describeIssues(error: z.ZodError): string {
  return error.issues
    .map((issue) => (issue.path.length ? `${issue.path.join(".")}: ` : "") + issue.message)
    .join("; ");
}

const noCompany = () => fail("unauthorized", "There is no company on this device yet.");

/**
 * The game on the device (CR-014): every former server endpoint as a command
 * with the same request and response schemas. Each command first applies any
 * arrivals that are due (as the server's lazy resolution did), runs on a copy
 * of the save through the single-writer queue, and is saved only if it changed
 * something.
 */
export class GameEngine {
  readonly core: EngineCore;
  readonly #table: CommandTable;

  constructor(private readonly options: GameEngineOptions) {
    const notifications = options.notifications;
    this.core = new EngineCore({
      ...options,
      afterSave: notifications ? (save, now) => notifications.sync(save, now) : options.afterSave,
    });
    this.#table = { ...commandTable(), ...options.overrides } as CommandTable;
  }

  now(): RealTime {
    return this.core.now();
  }

  /** Reschedules notifications from the current save (the Settings toggle changed). */
  resyncNotifications(): Promise<void> {
    const notifications = this.options.notifications;
    if (!notifications) return Promise.resolve();
    return this.core.read((save, now) => notifications.sync(save, now));
  }

  /** Asks for notification permission (right after the deal, decision 0.5.91). */
  requestNotificationPermission(): Promise<void> {
    return this.options.notifications?.requestPermission() ?? Promise.resolve();
  }

  /**
   * The resolution loop's pass (Step 14.6): applies any due arrivals and counts
   * rests and shop jobs that ended after `since`. Saves only when an arrival
   * was resolved; does nothing before a company exists.
   */
  resolveDue(
    since: RealTime | null,
  ): Promise<{ resolved: number; eventsPassed: number; now: RealTime }> {
    return this.core.write((save, now) => {
      if (!save)
        return { save: save!, result: { resolved: 0, eventsPassed: 0, now }, unchanged: true };
      const resolved = resolveArrivals(save, now);
      if (resolved > 0) pruneSave(save, now);
      const ended = (t: RealTime | null) => since !== null && t !== null && t > since && t <= now;
      const eventsPassed =
        save.pilots.filter((p) => ended(p.restEndsAt)).length +
        save.ships.filter((s) => ended(s.inShopUntil)).length;
      return { save, result: { resolved, eventsPassed, now }, unchanged: resolved === 0 };
    });
  }

  /** Runs one command; refusals throw `CommandError` with the server's codes. */
  async call<N extends CommandName>(name: N, input: RouteRequest<N>): Promise<RouteResponse<N>> {
    const route = routes[name];
    if (!route) {
      throw fail("not-found", `No command "${name}".`);
    }
    if (DEV_COMMANDS.includes(name) && !this.options.devTools) {
      throw fail("not-found", `No command "${name}".`);
    }
    const parsed = route.request.safeParse(input);
    if (!parsed.success) throw fail("validation-error", describeIssues(parsed.error));
    const result = await this.#run(name, parsed.data);
    if (this.options.validateResponses ?? true) {
      const checked = route.response.safeParse(result);
      if (!checked.success) {
        throw new Error(
          `Response for ${name} violates its schema: ${describeIssues(checked.error)}`,
        );
      }
    }
    return result as RouteResponse<N>;
  }

  async #run(name: CommandName, input: unknown): Promise<unknown> {
    const { random } = this.core;
    switch (name) {
      case "getServerTime": {
        const realTime = this.core.now();
        return { realTime, gameTime: realToGame(realTime, content.config) };
      }
      case "devAdvanceClock": {
        const clock = this.options.clock;
        if (!clock.advance) throw fail("not-found", "This clock can't be moved.");
        clock.advance((input as { advanceMs: number }).advanceMs);
        return { offsetMs: clock.offsetMs ?? 0, realTime: this.core.now() };
      }
      case "createGuest":
        // "Start your company": a new save when there is none; otherwise the existing one.
        return this.core.write((save, now) => {
          const next = save ?? startingSave(random, now);
          resolveArrivals(next, now);
          return {
            save: next,
            result: { playerId: next.saveId, state: playerState(next, now) },
            unchanged: save !== null,
          };
        });
      case "newCompany":
        // "Start a new company" (decision 0.5.74): the starting state with a new world seed.
        return this.core.write((save, now) => {
          if (!save) throw noCompany();
          const next = startingSave(random, now, {
            saveId: save.saveId,
            avoidSeed: save.player.worldSeed,
          });
          return { save: next, result: playerState(next, now) };
        });
      case "exportSave":
        return this.core.read(async (save) => {
          if (!save) throw noCompany();
          return { code: await encodeSave(save) };
        });
      case "importSave": {
        // Decoded before the queue, so a bad code never waits behind or blocks a write.
        const parsed = await decodeSave((input as { code: string }).code, this.options.migrate);
        if (!parsed.ok) throw fail("invalid-save", parsed.error);
        return this.core.write((_current, now) => {
          const next = parsed.save;
          resolveArrivals(next, now);
          pruneSave(next, now);
          return { save: next, result: { playerId: next.saveId, state: playerState(next, now) } };
        });
      }
      default: {
        const handler = this.#table[name] as (ctx: CommandContext, input: unknown) => unknown;
        return this.core.write((save, now) => {
          if (!save) throw noCompany();
          const before = JSON.stringify(save);
          resolveArrivals(save, now);
          const result = handler({ save, now, random }, input);
          pruneSave(save, now);
          return { save, result, unchanged: JSON.stringify(save) === before };
        });
      }
    }
  }
}

export { CommandError };