import type {
  SessionEntry,
  SessionStartEvent,
} from "@earendil-works/pi-coding-agent";

import {
  createRuntimeState,
  type DamageControlRuntimeState,
} from "ast-guard-core";

export const RUNTIME_STATE_CUSTOM_TYPE = "pi-damage-control.runtime-state";

interface PersistedRuntimeStateV1 {
  blockedRuleIds?: string[];
  version: 1;
  yolo: boolean;
}

interface PersistedRuntimeStateV2 {
  enabledOverrides?: [string, boolean][];
  version: 2;
  yolo: boolean;
}

interface PersistedRuntimeStateV3 {
  version: 3;
  yolo: boolean;
}

interface PersistedRuntimeStateV4 {
  dna: boolean;
  version: 4;
}

type PersistedRuntimeState =
  | PersistedRuntimeStateV1
  | PersistedRuntimeStateV2
  | PersistedRuntimeStateV3
  | PersistedRuntimeStateV4;

export type SessionStartReason = SessionStartEvent["reason"];

const RESTORE_RUNTIME_BY_SESSION_START_REASON = {
  fork: false,
  new: false,
  reload: true,
  resume: false,
  startup: false,
} satisfies Record<SessionStartReason, boolean>;

function isRecord(value: unknown): value is Record<string, unknown> {
  return typeof value === "object" && value !== null;
}

function isEnabledOverride(value: unknown): value is [string, boolean] {
  return (
    Array.isArray(value) &&
    value.length === 2 &&
    typeof value[0] === "string" &&
    typeof value[1] === "boolean"
  );
}

/**
 * 解析历史版本条目，迁移至 v4（仅保留 dna）。
 * v1（blockedRuleIds）与 v2（enabledOverrides）曾是 ag:block/ag:unblock 的
 * 持久化覆盖；该机制已移除。v3 将 yolo 重命名为 dna。
 */
function parsePersistedRuntimeState(
  value: unknown
): PersistedRuntimeState | undefined {
  if (
    !isRecord(value) ||
    (typeof value.yolo !== "boolean" && typeof value.dna !== "boolean")
  ) {
    return;
  }

  if (value.version === 1) {
    if (!Array.isArray(value.blockedRuleIds)) {
      return;
    }
    if (!value.blockedRuleIds.every((item) => typeof item === "string")) {
      return;
    }
    return { version: 1, yolo: value.yolo as boolean };
  }
  if (value.version === 2) {
    if (!Array.isArray(value.enabledOverrides)) {
      return;
    }
    if (!value.enabledOverrides.every(isEnabledOverride)) {
      return;
    }
    return { version: 2, yolo: value.yolo as boolean };
  }
  if (value.version === 3) {
    return { version: 3, yolo: value.yolo as boolean };
  }
  if (value.version === 4) {
    return { version: 4, dna: value.dna as boolean };
  }
  return;
}

function runtimeFromCustomEntry(
  entry: SessionEntry
): DamageControlRuntimeState | undefined {
  if (
    entry.type !== "custom" ||
    entry.customType !== RUNTIME_STATE_CUSTOM_TYPE
  ) {
    return;
  }
  const parsed = parsePersistedRuntimeState(entry.data);
  if (!parsed) {
    return;
  }
  // v1-v3 迁移：yolo → dna
  if (parsed.version === 1 || parsed.version === 2 || parsed.version === 3) {
    return createRuntimeState({ dna: parsed.yolo });
  }
  return createRuntimeState({ dna: parsed.dna });
}

export function snapshotRuntimeState(
  state: DamageControlRuntimeState
): PersistedRuntimeStateV4 {
  return {
    version: 4,
    dna: state.dna,
  };
}

export function runtimeForSessionStart(
  reason: SessionStartReason,
  entries: readonly SessionEntry[]
): DamageControlRuntimeState {
  if (!RESTORE_RUNTIME_BY_SESSION_START_REASON[reason]) {
    return createRuntimeState();
  }
  for (let index = entries.length - 1; index >= 0; index -= 1) {
    const entry = entries[index];
    if (!entry) {
      continue;
    }
    const restored = runtimeFromCustomEntry(entry);
    if (restored) {
      return restored;
    }
  }
  return createRuntimeState();
}