import { glob } from 'glob';
import { Config } from './conf';
import { promises as fs } from 'fs';
import { dirname, join as path_join } from 'path';
import { build_env_scope } from './env';
import { process_frontmatter } from '@doc-utils/markdown2html';
import { load_layout, Context, render_template, load_partials } from './template';
import { DateTime } from 'luxon';
import assert = require('assert');

interface BuildState {
	conf: Config;
	seen_files: Set<string>;
	env: Record<string, string>;
	partials?: Record<string, string>;
	layouts: Record<string, string>;
	made_directories: Set<string>;
	build_time: {
		iso: string;
		rfc2822: string;
	};
}

export async function build_docs_project(conf: Config) {
	const now = DateTime.now();
	const state: BuildState = {
		conf,
		seen_files: new Set<string>(),
		env: build_env_scope(conf),
		layouts: Object.create(null),
		made_directories: new Set<string>(),
		build_time: {
			iso: now.toISO(),
			rfc2822: now.toRFC2822(),
		},
	}

	if (conf.input.raw) {
		await copy_raw_files(state);
	}

	if (conf.input.text) {
		await render_text_file_templates(state);
	}

	if (conf.input.markdown) {
		// 
	}

	// todo...
}

async function copy_raw_files(state: BuildState) {
	const promises: Promise<any>[] = [ ];
	const files = await glob(state.conf.input.raw, {
		absolute: true,
		cwd: state.conf.input.root,
	});

	for (const in_file of files) {
		if (state.seen_files.has(in_file)) {
			continue;
		}

		state.seen_files.add(in_file);

		const out_file = map_input_file_to_output_file(state, in_file);

		promises.push(
			fs.copyFile(in_file, await out_file, 0o600)
		);
	}

	await Promise.all(promises);
}

async function render_text_file_templates(state: BuildState) {
	const promises: Promise<any>[] = [ ];
	const files = await glob(state.conf.input.text, {
		absolute: true,
		cwd: state.conf.input.root,
	});

	if (! state.partials) {
		state.partials = await load_partials(state.conf);
	}

	for (const in_file of files) {
		if (state.seen_files.has(in_file)) {
			continue;
		}

		state.seen_files.add(in_file);

		promises.push(
			render_text_file_template(state, in_file)
		);
	}

	await Promise.all(promises);
}

async function render_text_file_template(state: BuildState, in_file: string) {
	const out_file = map_input_file_to_output_file(state, in_file);
	const { frontmatter, document } = process_frontmatter(await fs.readFile(in_file, 'utf8'));
	
	let layout: string;
	const layout_file = frontmatter?.layout;

	if (layout_file) {
		if (! state.layouts[layout_file]) {
			state.layouts[layout_file] = await load_layout(state.conf, layout_file);
		}

		layout = state.layouts[layout_file];
	}

	const context: Context = {
		env: state.env,
		page: frontmatter,
		build_time: state.build_time,
	};

	const rendered = render_template(document, context, layout, structuredClone(state.partials));
	await fs.writeFile(await out_file, rendered, 'utf8');
}

async function map_input_file_to_output_file(state: BuildState, in_file: string, remove_exts?: string[], add_ext?: string) {
	assert(in_file.startsWith(state.conf.input.root), 'input file expected to be inside input root');
	let out_file = path_join(state.conf.output.root, in_file.slice(state.conf.input.root.length));

	if (remove_exts) {
		for (const ext of remove_exts) {
			if (out_file.endsWith(ext)) {
				out_file = out_file.slice(0, -ext.length);
				break;
			}
		}
	}

	if (add_ext) {
		out_file += add_ext;
	}

	const dir = dirname(out_file);
	
	if (! state.made_directories.has(dir)) {
		state.made_directories.add(dir);
		await fs.mkdir(dir, {
			mode: 0o700,
			recursive: true,
		});
	}

	return out_file;
}