/**
 * MP 差分测试共用工具:读取 scripts/mp-sync/gen-differential.py 生成的期望 JSON,登记偏差集合与实际偏差集合比对。
 * 偏差 key:`<sampleId>.status` / `<sampleId>.count` / `<sampleId>#<行号>.<字段>`。
 */
import { readFileSync, writeFileSync } from "node:fs";
import { dirname, join } from "node:path";
import { fileURLToPath } from "node:url";

export const HERE = dirname(fileURLToPath(import.meta.url));

export type DeviationKind = "intentional" | "missing" | "our_bug" | "mp_bug";
export interface Deviation {
  kind: DeviationKind;
  note: string;
  /** 仅在条件成立时才出现的偏差;local_tz_not_utc = 宿主本地时区偏移非 0 */
  condition?: "local_tz_not_utc";
}

function conditionHolds(d: Deviation): boolean {
  if (d.condition === "local_tz_not_utc") {
    return new Date("2026-09-26T00:00:00").getTimezoneOffset() !== 0;
  }
  return true;
}

export interface DifferentialDoc<S> {
  kind: string;
  generatedFrom: Record<string, string>;
  fields: string[];
  samples: S[];
  deviations: Record<string, Deviation>;
}

export function loadDoc<S>(name: string): DifferentialDoc<S> {
  return JSON.parse(readFileSync(join(HERE, name), "utf8")) as DifferentialDoc<S>;
}

export function readInput(rel: string): string {
  return readFileSync(join(HERE, rel), "utf8");
}

export interface Mismatch {
  key: string;
  mp: unknown;
  ours: unknown;
}

/** null / undefined 视为同一"缺省";其余按 JSON 结构比较 */
export function sameValue(a: unknown, b: unknown): boolean {
  if (a == null && b == null) return true;
  return JSON.stringify(a) === JSON.stringify(b);
}

export class FieldCollector {
  readonly mismatches: Mismatch[] = [];
  compared = 0;
  equal = 0;
  check(key: string, mp: unknown, ours: unknown): void {
    this.compared++;
    if (sameValue(mp, ours)) this.equal++;
    else this.mismatches.push({ key, mp, ours });
  }
}

/** 实际不一致集合 vs 登记集合:返回两个方向的差集(均为空才通过)。 */
export function diffAgainstRegistry(
  actual: Mismatch[],
  registry: Record<string, Deviation>,
): { unregistered: Mismatch[]; stale: string[] } {
  const actualKeys = new Set(actual.map((m) => m.key));
  return {
    unregistered: actual.filter((m) => !(m.key in registry)),
    stale: Object.entries(registry)
      .filter(([k, d]) => !actualKeys.has(k) && conditionHolds(d))
      .map(([k]) => k),
  };
}

/** 设置环境变量 DIFF_DUMP_DIR 时把实际不一致写成 <name>.mismatches.json(整理 deviations 用) */
export function dumpMismatches(name: string, ms: Mismatch[], stats?: { compared: number; equal: number }): void {
  const dir = process.env.DIFF_DUMP_DIR;
  if (dir) {
    writeFileSync(join(dir, `${name}.mismatches.json`), `${JSON.stringify({ stats, mismatches: ms }, null, 2)}\n`);
  }
}

export function formatMismatches(ms: Mismatch[]): string {
  return ms.map((m) => `${m.key}\n    mp:   ${JSON.stringify(m.mp)}\n    ours: ${JSON.stringify(m.ours)}`).join("\n");
}