/** @file Configuration for the esbuild bundler and build/watch commands.
 *
 * The bundler processes each entry point into a single file, each with no external dependencies and
 * minified. This primarily involves resolving all imports, along with some other transformations
 * (like TypeScript compilation).
 *
 * See the bundlers documentation for more information:
 * https://esbuild.github.io/getting-started/#bundling-for-node. */
import * as fs from 'node:fs/promises'
import * as path from 'node:path'
import * as url from 'node:url'

import * as esbuild from 'esbuild'
import * as esbuildPluginNodeModules from '@esbuild-plugins/node-modules-polyfill'
import esbuildPluginTime from 'esbuild-plugin-time'
import esbuildPluginYaml from 'esbuild-plugin-yaml'

import postcss from 'postcss'
import tailwindcss from 'tailwindcss'
import tailwindcssNesting from 'tailwindcss/nesting/index.js'

import * as utils from '../../utils'

// =================
// === Constants ===
// =================

const THIS_PATH = path.resolve(path.dirname(url.fileURLToPath(import.meta.url)))
const TAILWIND_CONFIG_PATH = path.resolve(THIS_PATH, 'tailwind.config.ts')

// =============================
// === Environment variables ===
// =============================

/** Mandatory build options. */
export interface Arguments {
    /** Path where bundled files are output. */
    outputPath: string
    /** `true` if in development mode (live-reload), `false` if in production mode. */
    devMode: boolean
}

/** Get arguments from the environment. */
export function argumentsFromEnv(): Arguments {
    const outputPath = path.resolve(utils.requireEnv('ENSO_BUILD_GUI'), 'assets')
    return { outputPath, devMode: false }
}

// =======================
// === Esbuild plugins ===
// =======================

/** A plugin to process all CSS files with Tailwind CSS. */
function esbuildPluginGenerateTailwind(): esbuild.Plugin {
    return {
        name: 'enso-generate-tailwind',
        setup: build => {
            /** An entry in the cache of already processed CSS files. */
            interface CacheEntry {
                contents: string
                lastModified: number
            }
            const cachedOutput: Record<string, CacheEntry> = {}
            let tailwindConfigLastModified = 0
            let tailwindConfigWasModified = true
            const cssProcessor = postcss([
                tailwindcss({
                    config: TAILWIND_CONFIG_PATH,
                }),
                tailwindcssNesting(),
            ])
            build.onStart(async () => {
                const tailwindConfigNewLastModified = (await fs.stat(TAILWIND_CONFIG_PATH)).mtimeMs
                tailwindConfigWasModified =
                    tailwindConfigLastModified !== tailwindConfigNewLastModified
                tailwindConfigLastModified = tailwindConfigNewLastModified
            })
            build.onLoad({ filter: /\.css$/ }, async loadArgs => {
                const lastModified = (await fs.stat(loadArgs.path)).mtimeMs
                let output = cachedOutput[loadArgs.path]
                if (!output || output.lastModified !== lastModified || tailwindConfigWasModified) {
                    console.log(`Processing CSS file '${loadArgs.path}'.`)
                    const content = await fs.readFile(loadArgs.path, 'utf8')
                    const result = await cssProcessor.process(content, { from: loadArgs.path })
                    console.log(`Processed CSS file '${loadArgs.path}'.`)
                    output = { contents: result.css, lastModified }
                    cachedOutput[loadArgs.path] = output
                }
                return {
                    contents: output.contents,
                    loader: 'css',
                    watchFiles: [loadArgs.path, TAILWIND_CONFIG_PATH],
                }
            })
        },
    }
}

// ================
// === Bundling ===
// ================

/** Generate the bundler options. */
export function bundlerOptions(args: Arguments) {
    const { outputPath, devMode } = args
    // This is required to prevent TypeScript from narrowing `true` to `boolean`.
    // eslint-disable-next-line no-restricted-syntax
    const trueBoolean = true as boolean
    const buildOptions = {
        absWorkingDir: THIS_PATH,
        bundle: trueBoolean,
        entryPoints: [path.resolve(THIS_PATH, 'src', 'tailwind.css')],
        outdir: outputPath,
        outbase: 'src',
        plugins: [
            esbuildPluginNodeModules.NodeModulesPolyfillPlugin(),
            esbuildPluginTime(),
            // This is not strictly needed because the cloud frontend does not use
            // the Project Manager, however it is very difficult to conditionally exclude a module.
            esbuildPluginYaml.yamlPlugin({}),
            esbuildPluginGenerateTailwind(),
        ],
        define: {
            // We are defining constants, so it should be `CONSTANT_CASE`.
            /* eslint-disable @typescript-eslint/naming-convention */
            /** Whether the application is being run locally. This enables a service worker that
             * properly serves `/index.html` to client-side routes like `/login`. */
            IS_DEV_MODE: JSON.stringify(devMode),
            /** Overrides the redirect URL for OAuth logins in the production environment.
             * This is needed for logins to work correctly under `./run gui watch`. */
            REDIRECT_OVERRIDE: 'undefined',
            /* eslint-enable @typescript-eslint/naming-convention */
        },
        pure: ['assert'],
        sourcemap: trueBoolean,
        minify: !devMode,
        metafile: trueBoolean,
        format: 'esm',
        platform: 'browser',
        color: trueBoolean,
    } satisfies esbuild.BuildOptions
    // The narrower type is required to avoid non-null assertions elsewhere.
    // The intersection with `esbuild.BuildOptions` is required to allow adding extra properties.
    const correctlyTypedBuildOptions: esbuild.BuildOptions & typeof buildOptions = buildOptions
    return correctlyTypedBuildOptions
}

/** esbuild options for bundling (one-off build) the package.
 *
 * Relies on the environment variables to be set. */
export function bundleOptions() {
    return bundlerOptions(argumentsFromEnv())
}