import { createHash } from "node:crypto";
import { existsSync, readFileSync } from "node:fs";
import { readFile, stat } from "node:fs/promises";
import { pathToFileURL } from "node:url";
import type { TranslationMap, TranslationMemoryEntry } from "./control-ui-i18n-sync-plan.ts";

async function importControlUiLocaleModule<T>(filePath: string): Promise<T> {
  const stats = await stat(filePath);
  return (await import(`${pathToFileURL(filePath).href}?ts=${stats.mtimeMs}`)) as T;
}

export async function loadControlUiLocaleCatalog(
  filePath: string,
  exportName: string,
): Promise<TranslationMap | null> {
  if (!existsSync(filePath)) {
    return null;
  }
  const module = await importControlUiLocaleModule<Record<string, TranslationMap>>(filePath);
  return module[exportName] ?? null;
}

export async function loadControlUiSourceCatalog(
  sourceLocalePath: string,
  activitySourceLocalePath: string,
  sessionPlacementSourceLocalePath: string,
): Promise<TranslationMap> {
  const source = await loadControlUiLocaleCatalog(sourceLocalePath, "en");
  const activitySource = (
    await importControlUiLocaleModule<{
      registerActivityEnglish: { catalog: TranslationMap };
    }>(activitySourceLocalePath)
  ).registerActivityEnglish.catalog;
  const sessionPlacementSource = (
    await importControlUiLocaleModule<{
      registerSessionPlacementEnglish: { catalog: TranslationMap };
    }>(sessionPlacementSourceLocalePath)
  ).registerSessionPlacementEnglish.catalog;
  if (!source || !activitySource || !sessionPlacementSource) {
    throw new Error("Control UI English source catalogs are incomplete");
  }
  return mergeControlUiTranslationMaps(source, activitySource, sessionPlacementSource);
}

export async function readControlUiSourceCatalog(
  sourceLocalePath: string,
  activitySourceLocalePath: string,
  sessionPlacementSourceLocalePath: string,
): Promise<string> {
  const sources = await Promise.all(
    [sourceLocalePath, activitySourceLocalePath, sessionPlacementSourceLocalePath].map((filePath) =>
      readFile(filePath, "utf8"),
    ),
  );
  return sources.join("\n");
}

export function hashControlUiTranslationText(text: string): string {
  return createHash("sha256").update(text.trim().split(/\s+/).join(" ")).digest("hex");
}

export function mergeControlUiTranslationMaps(
  ...maps: ReadonlyArray<TranslationMap>
): TranslationMap {
  const merged: TranslationMap = {};
  const mergeInto = (target: TranslationMap, source: TranslationMap): void => {
    for (const [key, value] of Object.entries(source)) {
      if (typeof value === "string") {
        target[key] = value;
        continue;
      }
      const existing = target[key];
      const nested = typeof existing === "object" ? existing : {};
      target[key] = nested;
      mergeInto(nested, value);
    }
  };
  for (const map of maps) {
    mergeInto(merged, map);
  }
  return merged;
}

export function loadControlUiTranslationMemory(
  filePath: string,
): Map<string, TranslationMemoryEntry> {
  const entries = new Map<string, TranslationMemoryEntry>();
  if (!existsSync(filePath)) {
    return entries;
  }
  for (const line of readFileSync(filePath, "utf8").split("\n")) {
    if (!line.trim()) {
      continue;
    }
    const entry = JSON.parse(line) as TranslationMemoryEntry;
    if (entry.cache_key && entry.translated.trim()) {
      entries.set(entry.cache_key, entry);
    }
  }
  return entries;
}

function setControlUiCatalogValue(catalog: TranslationMap, key: string, value: string): void {
  const parts = key.split(".");
  let current = catalog;
  for (const part of parts.slice(0, -1)) {
    const existing = current[part];
    if (!existing || typeof existing === "string") {
      current[part] = {};
    }
    current = current[part] as TranslationMap;
  }
  current[parts[parts.length - 1]!] = value;
}

export function materializeControlUiLocaleCatalog(
  sourceFlat: ReadonlyMap<string, string>,
  memory: ReadonlyMap<string, TranslationMemoryEntry>,
): TranslationMap {
  const translations = new Map<string, string>();

  for (const entry of memory.values()) {
    for (const key of [entry.segment_id, ...(entry.segment_ids ?? [])]) {
      const source = sourceFlat.get(key);
      if (source === undefined || entry.text_hash !== hashControlUiTranslationText(source)) {
        continue;
      }
      translations.set(key, entry.translated);
    }
  }

  const catalog: TranslationMap = {};
  for (const key of sourceFlat.keys()) {
    const translated = translations.get(key);
    if (translated !== undefined) {
      setControlUiCatalogValue(catalog, key, translated);
    }
  }
  return catalog;
}