import { fnv1a64 } from "./replay.mjs";

export const IO_ACK_SCHEMA = "sim_io_ack.v1";
const STATUSES = new Set(["pending", "acked", "timed_out", "aborted"]);

function clone(value) { return structuredClone(value); }

export class IoAckTracker {
  constructor() { this.reset(); }
  reset() { this.state = { schema: IO_ACK_SCHEMA, tick: 0, commands: [] }; return this.export(); }
  export() { const value = clone(this.state); return { ...value, state_hash: fnv1a64(value) }; }
  hash() { return this.export().state_hash; }
  find(operationId) { return this.state.commands.find((command) => command.operation_id === operationId); }
  issue(operationId, kind, tick, timeoutTicks = 10) {
    if (typeof operationId !== "string" || operationId.length === 0 || typeof kind !== "string" || !Number.isSafeInteger(tick) || tick < this.state.tick || !Number.isSafeInteger(timeoutTicks) || timeoutTicks < 1 || timeoutTicks > 1000000) return { status: "error", code: "io_ack_argument" };
    const existing = this.find(operationId);
    if (existing) return existing.status === "acked" ? { status: "verified", replay: true, command: clone(existing), state: this.export() } : { status: "error", code: "io_ack_duplicate", command: clone(existing), state: this.export() };
    const command = { operation_id: operationId, kind, issued_tick: tick, deadline_tick: tick + timeoutTicks, status: "pending", ack_tick: null, side_effect_count: 0 };
    this.state.tick = tick; this.state.commands.push(command);
    return { status: "verified", command: clone(command), state: this.export() };
  }
  step(tick) {
    if (!Number.isSafeInteger(tick) || tick < this.state.tick) return { status: "error", code: "io_ack_tick_regression", state: this.export() };
    this.state.tick = tick;
    for (const command of this.state.commands) if (command.status === "pending" && tick >= command.deadline_tick) command.status = "timed_out";
    return { status: "verified", command: "IO_TICK", state: this.export() };
  }
  ack(operationId, tick) {
    const command = this.find(operationId);
    if (!command) return { status: "error", code: "io_ack_missing", state: this.export() };
    if (!Number.isSafeInteger(tick) || tick < this.state.tick) return { status: "error", code: "io_ack_tick_regression", state: this.export() };
    this.state.tick = tick;
    if (command.status !== "pending") return { status: "error", code: command.status === "timed_out" ? "io_ack_late" : "io_ack_state", command: clone(command), state: this.export() };
    command.status = "acked"; command.ack_tick = tick; command.side_effect_count = 1;
    return { status: "verified", command: clone(command), state: this.export() };
  }
  abort(operationId) {
    const command = this.find(operationId);
    if (!command) return { status: "error", code: "io_ack_missing", state: this.export() };
    if (command.status === "acked") return { status: "error", code: "io_ack_too_late", command: clone(command), state: this.export() };
    command.status = "aborted";
    return { status: "verified", command: clone(command), state: this.export() };
  }
  restore(value) {
    if (!value || value.schema !== IO_ACK_SCHEMA || !Array.isArray(value.commands)) throw new Error("io_ack_restore_schema");
    const unsigned = { ...value }; delete unsigned.state_hash;
    if (value.state_hash !== fnv1a64(unsigned)) throw new Error("io_ack_restore_hash");
    if (value.commands.some((command) => !STATUSES.has(command.status))) throw new Error("io_ack_restore_status");
    this.state = clone(unsigned); return this.export();
  }
}