import {
	createHighlighter,
	type Highlighter,
	type BundledTheme,
	type BundledLanguage,
	bundledLanguages,
	bundledThemes,
} from "shiki"

// Extend BundledLanguage to include 'txt' because Shiki supports this but it is
// not listed in the bundled languages
export type ExtendedLanguage = BundledLanguage | "txt"

// Map common language aliases to their Shiki BundledLanguage equivalent
const languageAliases: Record<string, ExtendedLanguage> = {
	// Plain text variants
	text: "txt",
	plaintext: "txt",
	plain: "txt",

	// Shell/Bash variants
	sh: "shell",
	bash: "shell",
	zsh: "shell",
	shellscript: "shell",
	"shell-script": "shell",
	console: "shell",
	terminal: "shell",

	// JavaScript variants
	js: "javascript",
	node: "javascript",
	nodejs: "javascript",

	// TypeScript variants
	ts: "typescript",

	// Python variants
	py: "python",
	python3: "python",
	py3: "python",

	// Ruby variants
	rb: "ruby",

	// Markdown variants
	md: "markdown",

	// C++ variants
	cpp: "c++",
	cc: "c++",

	// C# variants
	cs: "c#",
	csharp: "c#",

	// HTML variants
	htm: "html",

	// YAML variants
	yml: "yaml",

	// Docker variants
	dockerfile: "docker",

	// CSS variants
	styles: "css",
	style: "css",

	// JSON variants
	jsonc: "json",
	json5: "json",

	// XML variants
	xaml: "xml",
	xhtml: "xml",
	svg: "xml",

	// SQL variants
	mysql: "sql",
	postgresql: "sql",
	postgres: "sql",
	pgsql: "sql",
	plsql: "sql",
	oracle: "sql",
}

// Track which languages we've warned about to avoid duplicate warnings
const warnedLanguages = new Set<string>()

// Normalize language to a valid Shiki language
export function normalizeLanguage(language: string | undefined): ExtendedLanguage {
	if (language === undefined) {
		return "txt"
	}

	// Convert to lowercase for consistent matching
	const normalizedInput = language.toLowerCase()

	// If it's already a valid bundled language, return it
	if (normalizedInput in bundledLanguages) {
		return normalizedInput as BundledLanguage
	}

	// Check if it's an alias
	if (normalizedInput in languageAliases) {
		return languageAliases[normalizedInput]
	}

	// Warn about unrecognized language and default to txt (only once per language)
	if (language !== "txt" && !warnedLanguages.has(language)) {
		console.warn(`[Shiki] Unrecognized language '${language}', defaulting to txt.`)
		warnedLanguages.add(language)
	}

	return "txt"
}

// Export function to check if a language is loaded
export const isLanguageLoaded = (language: string): boolean => {
	return state.loadedLanguages.has(normalizeLanguage(language))
}

// Artificial delay for testing language loading (ms) - for testing
const LANGUAGE_LOAD_DELAY = 0

// Common languages for first-stage initialization
const initialLanguages: BundledLanguage[] = ["shell", "log"]

// Singleton state
const state: {
	instance: Highlighter | null
	instanceInitPromise: Promise<Highlighter> | null
	loadedLanguages: Set<ExtendedLanguage>
	pendingLanguageLoads: Map<ExtendedLanguage, Promise<void>>
} = {
	instance: null,
	instanceInitPromise: null,
	loadedLanguages: new Set<ExtendedLanguage>(["txt"]),
	pendingLanguageLoads: new Map(),
}

export const getHighlighter = async (language?: string): Promise<Highlighter> => {
	try {
		const shikilang = normalizeLanguage(language)

		// Initialize highlighter if needed
		if (!state.instanceInitPromise) {
			state.instanceInitPromise = (async () => {
				// const startTime = performance.now()
				// console.debug("[Shiki] Initialization started...")

				const instance = await createHighlighter({
					themes: Object.keys(bundledThemes) as BundledTheme[],
					langs: initialLanguages,
				})

				// const elapsed = Math.round(performance.now() - startTime)
				// console.debug(`[Shiki] Initialization complete (${elapsed}ms)`)

				state.instance = instance

				// Track initially loaded languages
				initialLanguages.forEach((lang) => state.loadedLanguages.add(lang))

				return instance
			})()
		}

		// Wait for initialization to complete
		const instance = await state.instanceInitPromise

		// Load requested language if needed (txt is already in loadedLanguages)
		if (!state.loadedLanguages.has(shikilang)) {
			// Check for existing pending load
			let loadingPromise = state.pendingLanguageLoads.get(shikilang)

			if (!loadingPromise) {
				// const loadStart = performance.now()
				// Create new loading promise
				loadingPromise = (async () => {
					try {
						// Add artificial delay for testing if nonzero
						if (LANGUAGE_LOAD_DELAY > 0) {
							await new Promise((resolve) => setTimeout(resolve, LANGUAGE_LOAD_DELAY))
						}

						await instance.loadLanguage(shikilang as BundledLanguage)
						state.loadedLanguages.add(shikilang)

						// const loadTime = Math.round(performance.now() - loadStart)
						// console.debug(`[Shiki] Loaded language ${shikilang} (${loadTime}ms)`)
					} catch (error) {
						console.error(`[Shiki] Failed to load language ${shikilang}:`, error)
						throw error
					} finally {
						// Clean up pending promise after completion
						state.pendingLanguageLoads.delete(shikilang)
					}
				})()

				// Store the promise
				state.pendingLanguageLoads.set(shikilang, loadingPromise)
			}

			await loadingPromise
		}

		return instance
	} catch (error) {
		console.error("[Shiki] Error in getHighlighter:", error)
		throw error
	}
}