import prettier from "prettier";
import type { LanguageInfo, TranslationSchema } from "./types";
import { unique } from "./utils";

export interface Translations {
	[fileName: string]: TranslationSchema;
}

// Assumes BCP 47 locale format (e.g. 'en-GB', 'zh-Hans', 'zh-Hans-CN').
// The ISO-639-1 key is always the first hyphen-delimited segment.
function getIso1Key(code: string): string {
	return code.includes("-") ? code.split("-")[0] : code;
}

/**
 * Builds the body of the `iso1ToLocale` map (ISO-639-1 prefix -> full locale).
 *
 * Several locales can share the same ISO-639-1 prefix (e.g. en-GB/en-US,
 * zh-Hans/zh-Hant, pt-PT/pt-BR). Emitting one entry per locale produced a
 * literal with duplicate object keys, where the last declaration silently
 * overwrote the previous ones. To avoid that:
 *  - the default locale is processed first, so a shared prefix maps to it;
 *  - remaining prefix collisions resolve to the first listed locale.
 * The result always contains exactly one entry per prefix.
 */
function buildIso1ToLocale(
	languages: LanguageInfo[],
	defaultLocale: string,
): string {
	const ordered: LanguageInfo[] = [];
	for (const lang of languages) {
		if (lang.code === defaultLocale) ordered.push(lang);
	}
	for (const lang of languages) {
		if (lang.code !== defaultLocale) ordered.push(lang);
	}

	const seen = new Map<string, string>();
	for (const { code } of ordered) {
		const key = getIso1Key(code);
		if (!seen.has(key)) {
			seen.set(key, code);
		}
	}

	return Array.from(seen, ([key, code]) => `${key}: '${code}'`).join(", ");
}

function extractTranslationParameters(translation: string): string[] {
	const match = translation.match(/{{\w+}}/g) || [];

	return match.map((x) => x.replace(/[{}]/g, ""));
}

function transformKeys<T extends Record<string, unknown>>(
	obj: T,
	transform: (key: string) => string,
): T {
	const transformed = Object.fromEntries(
		Object.entries(obj).map(([key, value]) => [transform(key), value]),
	);

	return transformed as T;
}

function getFileKeys(
	translations: TranslationSchema,
): Record<string, string[]> {
	return Object.entries(translations).reduce(
		(acc, [key, value]) => {
			return typeof value === "string"
				? { ...acc, [key]: extractTranslationParameters(value) }
				: {
						...acc,
						...transformKeys(
							getFileKeys(value),
							(nestedKey) => `${key}.${nestedKey}`,
						),
					};
		},
		{} as Record<string, string[]>,
	);
}

function getKeys(
	namespace: string,
	file: TranslationSchema,
): Record<string, string[]> {
	return transformKeys(getFileKeys(file), (key) => `${namespace}:${key}`);
}

const removeJsonExtension = (file: string): string =>
	file.replace(/\.json$/, "");

export async function generateKeys({
	languages,
	translations,
	prettierConfig,
	defaultLocale,
}: {
	languages: LanguageInfo[];
	translations: Translations;
	defaultLocale: string;
	prettierConfig: prettier.Options;
}): Promise<string> {
	const namespaces = Object.keys(translations).map(removeJsonExtension);

	// Handle empty translations case
	if (namespaces.length === 0) {
		const content = await prettier.format(
			`// This file was autogenerated on ${new Date().toISOString()}.
  // DO NOT EDIT THIS FILE.

  export const locales = [${languages
		.map((lng) => `'${lng.code}'`)
		.join(", ")}] as const;
  export type Locale = typeof locales[number];
  export const defaultLocale: Locale = '${defaultLocale}';

  export const iso1ToLocale: { [key: string]: Locale } = {${buildIso1ToLocale(
		languages,
		defaultLocale,
	)}}

  export const languages: Array<{ code: Locale; englishName: string; localName: string }> = ${JSON.stringify(
		languages,
	)};

  export type Namespace = never;
  export const namespaces: Namespace[] = [];
  
  export type TranslationKeyWithoutOptions = never;
  export type TranslationWithOptions = {};
  type TranslationKeyWithOptions = keyof TranslationWithOptions;

  export type TranslationKey =
    | TranslationKeyWithoutOptions
    | TranslationKeyWithOptions;
  export type Translator = {
    (key: TranslationKeyWithoutOptions, options?: { count: number }): string;
    <T extends TranslationKeyWithOptions>(
      key: T,
      options: TranslationWithOptions[T] & { count?: number }
    ): string;
  };
  `,
			{ ...prettierConfig, parser: "typescript" },
		);
		return content;
	}

	const allKeys = Object.entries(translations)
		.map(([namespace, file]) => getKeys(removeJsonExtension(namespace), file))
		.reduce((acc, cur) => {
			return {
				...acc,
				...cur,
			};
		}, {});
	const { parameterized, simple } = Object.entries(allKeys).reduce(
		(acc, [key, parameters]) => {
			if (parameters.length > 0) {
				return {
					...acc,
					parameterized: { ...acc.parameterized, [key]: unique(parameters) },
				};
			}
			return { ...acc, simple: [...acc.simple, key] };
		},
		{ parameterized: {}, simple: [] } as {
			parameterized: Record<string, string[]>;
			simple: string[];
		},
	);

	const content = await prettier.format(
		`// This file was autogenerated on ${new Date().toISOString()}.
  // DO NOT EDIT THIS FILE.

  export const locales = [${languages
		.map((lng) => `'${lng.code}'`)
		.join(", ")}] as const;
  export type Locale = typeof locales[number];
  export const defaultLocale: Locale = '${defaultLocale}';

  export const iso1ToLocale: { [key: string]: Locale } = {${buildIso1ToLocale(
		languages,
		defaultLocale,
	)}}

  export const languages: Array<{ code: Locale; englishName: string; localName: string }> = ${JSON.stringify(
		languages,
	)};

  export type Namespace = ${namespaces
		.map((namespace) => `'${namespace}'`)
		.join(" | ")};
  export const namespaces: Namespace[] = [${namespaces
		.map((namespace) => `'${namespace}'`)
		.join(" , ")}];
  
  export type TranslationKeyWithoutOptions = ${
		simple.length > 0 ? simple.map((key) => `'${key}'`).join(" | ") : "never"
	};
  export type TranslationWithOptions = {
    ${Object.entries(parameterized).map(
			([key, parameters]) =>
				`'${key}': { ${parameters
					.map(
						(parameter) =>
							`'${parameter}': ${parameter === "count" ? "number" : "string"}`,
					)
					.join(",")} }`,
		)}
    };
    type TranslationKeyWithOptions = keyof TranslationWithOptions;

  export type TranslationKey =
    | TranslationKeyWithoutOptions
    | TranslationKeyWithOptions;
  export type Translator = {
    (key: TranslationKeyWithoutOptions, options?: { count: number }): string;
    <T extends TranslationKeyWithOptions>(
      key: T,
      options: TranslationWithOptions[T] & { count?: number }
    ): string;
  };
  `,
		{ ...prettierConfig, parser: "typescript" },
	);

	return content;
}