import type { SimpleElement } from '@simple-dom/interface';

import type { Nullable } from '../core.js';
import type { AppendingBlock } from '../dom/attributes.js';
import type { Cursor } from '../dom/bounds.js';
import type { EvaluationContext } from '../program.js';
import type { BlockMetadata } from '../template.js';
import type { DynamicScope, Scope, ScopeSlot } from './scope.js';
import type { UpdatingBlockOpcode, UpdatingOpcode } from './vm.js';

export type MachineRegisters = [$pc: number, $ra: number, $fp: number, $sp: number];

export type DebugRegisters = readonly [
  $pc: number,
  $ra: number,
  $fp: number,
  $sp: number,
  $s0: unknown,
  $s1: unknown,
  $t0: unknown,
  $t1: unknown,
  $v0: unknown,
];

type Handle = number;

export interface DebugTemplates {
  readonly active: Nullable<BlockMetadata>;
  register(handle: Handle, metadata: BlockMetadata): void;
  willCall(handle: Handle): void;
  return(): void;
}

export interface DebugVmTrace {
  readonly willCall: (handle: Handle) => void;
  readonly return: () => void;
  readonly register: (handle: Handle, metadata: BlockMetadata) => void;
}

/**
 * All parts of `DebugVmState` are _snapshots_. They will not change if the piece of VM state that
 * they reference changes.
 */
export interface DebugVmSnapshot {
  /**
   * These values are the same for the entire program
   */
  readonly context: EvaluationContext;

  /**
   * These values can change for each opcode. You can get a snapshot a specific stack by calling
   * `stacks.<name>.snapshot()`.
   */
  readonly stacks: DebugStacks;

  readonly elements: {
    blocks: AppendingBlock[];
    cursors: Cursor[];
    constructing: Nullable<SimpleElement>;
  };

  readonly stack: unknown[];
  readonly scope: ScopeSlot[];
  readonly registers: DebugRegisters;
  readonly template: Nullable<BlockMetadata>;
}

export interface DebugStacks {
  scope: Scope[];
  dynamicScope: DynamicScope[];
  updating: UpdatingOpcode[][];
  cache: UpdatingOpcode[];
  list: UpdatingBlockOpcode[];
  destroyable: object[];
}