/**
 * Config loader functionality for ts-for-gir
 */

import { dirname, resolve } from "node:path";
import { pathToFileURL } from "node:url";
import type { ConfigFlags, OptionsGeneration, UserConfig, UserConfigLoadResult } from "@ts-for-gir/lib";
import { APP_NAME, isEqual } from "@ts-for-gir/lib";
import { type Options as ConfigSearchOptions, cosmiconfig } from "cosmiconfig";
import { setConfigFilePath } from "./config-writer.ts";
import { defaults } from "./defaults.ts";
import { docOptions, options } from "./options.ts";

/**
 * The user can create a `.ts-for-girrc` file for his default configs,
 * this method load this config file an returns the user configuration
 * @param configName If the user uses a custom config file name
 */
export async function loadConfigFile(configName?: string): Promise<UserConfigLoadResult | null> {
	const configSearchOptions: Partial<ConfigSearchOptions> = {
		loaders: {
			// ESM loader. cosmiconfig hands us an absolute filesystem path; Node's import()
			// tolerates that as a non-spec extension, but spec-compliant runtimes (GJS /
			// SpiderMonkey) reject it with "Module not found: <abs-path>". Convert to a
			// file:// URL so the loader works in both runtimes.
			".js": async (filepath) => {
				const file = await import(pathToFileURL(filepath).href);

				// Files with `exports.default = { ... }`
				if (file?.default?.default) {
					return file.default.default as Partial<UserConfig>;
				}
				// Files with `export default { ... }`
				if (file?.default) {
					return file.default as Partial<UserConfig>;
				}
				// Files with `export { ... }`
				return file as Partial<UserConfig>;
			},
		},
	};

	if (configName) {
		configSearchOptions.searchPlaces = [configName];
	}

	const configFile: UserConfigLoadResult | null = await cosmiconfig(APP_NAME, configSearchOptions).search();

	if (configFile?.filepath) {
		setConfigFilePath(configFile.filepath);
	}

	return configFile;
}

/**
 * Convert UserConfig to OptionsGeneration
 */
export function getOptionsGeneration(config: UserConfig): OptionsGeneration {
	const generateConfig: OptionsGeneration = {
		...config,
	};
	return generateConfig;
}

/**
 * Parse `Namespace=npm-package` strings (from repeatable `--external-package` flag) into a
 * map. Silently drops entries that don't contain `=`. Empty input returns undefined so the
 * field stays absent in the merged config (rather than `{}`, which would shadow rc values).
 */
function parseExternalPackagePairs(pairs: string[] | undefined): Record<string, string> | undefined {
	if (!pairs || pairs.length === 0) return undefined;
	const map: Record<string, string> = {};
	for (const pair of pairs) {
		const eq = pair.indexOf("=");
		if (eq < 1) continue;
		const ns = pair.slice(0, eq).trim();
		const pkg = pair.slice(eq + 1).trim();
		if (ns && pkg) map[ns] = pkg;
	}
	return Object.keys(map).length > 0 ? map : undefined;
}

/**
 * Validate the configuration
 */
export function validate(config: UserConfig): UserConfig {
	return config;
}

/**
 * Merge a single config value from file config to user config
 * @param userConfig The user config object to update
 * @param configFileData The config file data to merge from
 * @param key The config key to merge
 * @param optionDefault The default value from options
 * @param validator Optional validation function
 */
const isBoolean = (v: unknown) => typeof v === "boolean";

function mergeConfigValue<K extends keyof UserConfig>(
	userConfig: UserConfig,
	configFileData: Partial<UserConfig>,
	key: K,
	optionDefault: unknown,
	validator?: (value: unknown) => boolean,
): void {
	const fileValue = configFileData[key];
	const userValue = userConfig[key];

	// Skip if no file value
	if (fileValue === undefined) return;

	// Apply validator if provided
	if (validator && !validator(fileValue)) return;

	// Check if user value is default
	const isDefault =
		userValue === optionDefault ||
		(Array.isArray(userValue) && Array.isArray(optionDefault) && isEqual(userValue, optionDefault));

	if (isDefault) {
		(userConfig[key] as UserConfig[K]) = fileValue as UserConfig[K];
	}
}

/**
 * Loads the values of the config file and concatenate them with passed cli flags / arguments.
 * The values from config file are preferred if the cli flag value is the default (and so not set / overwritten)
 * @param cliOptions CLI options passed by the user
 */
export async function load(cliOptions: ConfigFlags): Promise<UserConfig> {
	const configFile = await loadConfigFile(cliOptions.configName);
	const configFileData = configFile?.config || {};

	// `--external-package GLib=@girs/glib-2.0` arrives as a string[]; collapse to Record.
	// Drop the raw array so it doesn't pollute the merged UserConfig surface.
	const externalPackagesFromCli = parseExternalPackagePairs(
		(cliOptions as { externalPackage?: string[] }).externalPackage,
	);
	const { externalPackage: _externalPackage, ...cliOptionsClean } = cliOptions as ConfigFlags & {
		externalPackage?: string[];
	};

	const userConfig: UserConfig = {
		...cliOptionsClean,
	};
	if (externalPackagesFromCli) {
		userConfig.externalPackages = externalPackagesFromCli;
	}

	if (configFileData) {
		// Boolean options — config file overrides CLI defaults
		const booleanKeys: Array<[keyof UserConfig, unknown]> = [
			["verbose", options.verbose.default],
			["ignoreVersionConflicts", options.ignoreVersionConflicts.default],
			["print", options.print.default],
			["noNamespace", options.noNamespace.default],
			["noComments", options.noComments.default],
			["promisify", options.promisify.default],
			["workspace", options.workspace.default],
			["onlyVersionPrefix", options.onlyVersionPrefix.default],
			["noPrettyPrint", options.noPrettyPrint.default],
			["noAdvancedVariants", options.noAdvancedVariants.default],
			["package", options.package.default],
			["reporter", options.reporter.default],
			["externalDeps", options.externalDeps.default],
			["allowMissingDeps", options.allowMissingDeps.default],
			["combined", docOptions.combined.default],
			["merge", docOptions.merge.default],
		];
		for (const [key, defaultVal] of booleanKeys) {
			mergeConfigValue(userConfig, configFileData, key, defaultVal, isBoolean);
		}

		// String options — config file overrides CLI defaults
		const stringKeys: Array<[keyof UserConfig, unknown]> = [
			["npmScope", options.npmScope.default],
			["reporterOutput", options.reporterOutput.default],
			["depVersionFormat", undefined],
			["theme", docOptions.theme.default],
			["sourceLinkTemplate", undefined],
			["readme", undefined],
			["jsonDir", undefined],
		];
		for (const [key, defaultVal] of stringKeys) {
			mergeConfigValue(userConfig, configFileData, key, defaultVal);
		}

		// Array options — config file overrides CLI defaults
		const arrayKeys: Array<[keyof UserConfig, unknown]> = [
			["ignore", options.ignore.default],
			["modules", options.modules.default],
		];
		for (const [key, defaultVal] of arrayKeys) {
			mergeConfigValue(userConfig, configFileData, key, defaultVal);
		}

		// girDirectories: rc-file entries are prepended to the current dirs (CLI-provided or
		// system defaults) rather than replacing them. This lets projects add local GIR dirs
		// (e.g. a Vala build output) without having to enumerate all system paths in the rc.
		// To use ONLY the specified dirs (no system fallback), pass --girDirectories on the CLI.
		if (configFileData.girDirectories?.length) {
			const current = userConfig.girDirectories as string[];
			const toAdd = (configFileData.girDirectories as string[]).filter((d) => !current.includes(d));
			if (toAdd.length > 0) {
				userConfig.girDirectories = [...toAdd, ...current];
			}
		}

		// Special handling for root
		if (userConfig.root === options.root.default && (configFileData.root || configFile?.filepath)) {
			userConfig.root =
				configFileData.root || (configFile?.filepath ? dirname(configFile.filepath) : (options.root.default as string));
		}

		// Special handling for outdir (override with config file value if still at a default)
		const isDefaultOutdir = userConfig.outdir === options.outdir.default || userConfig.outdir === defaults.docOutdir;
		if (isDefaultOutdir && configFileData.outdir) {
			userConfig.outdir = userConfig.print ? null : configFileData.outdir;
		}

		// externalPackages is a Record<string, string> in rc files; CLI overrides take precedence.
		if (!externalPackagesFromCli && configFileData.externalPackages) {
			userConfig.externalPackages = configFileData.externalPackages;
		}
	}

	// Make paths absolute relative to root
	const resolveToRoot = (path: string) => (path.startsWith("/") ? path : resolve(userConfig.root, path));

	if (userConfig.outdir) {
		userConfig.outdir = resolveToRoot(userConfig.outdir);
	}
	if (userConfig.jsonDir) {
		userConfig.jsonDir = resolveToRoot(userConfig.jsonDir);
	}
	if (userConfig.girDirectories) {
		userConfig.girDirectories = userConfig.girDirectories.map(resolveToRoot);
	}
	return validate(userConfig);
}