import { BuildOptions } from 'esbuild'
import { ParsedCommandLine, ScriptTarget, ModuleKind } from 'typescript'

import { CliArgs } from './interfaces'

/**
 * transform tsconfig to esbuild config
 * key: keyof TransformOptions
 */
export class ConfigConverter {
  private cwd: string
  private parsedCommandLine: ParsedCommandLine
  private esbuildConfig: BuildOptions = {
    bundle: false,
  }

  public constructor({
    cwd,
    parsedCommandLine,
  }: {
    cwd: string
    parsedCommandLine: ParsedCommandLine
  }) {
    this.cwd = cwd
    this.parsedCommandLine = parsedCommandLine
  }

  public mergeCliArgs(args: CliArgs = {}) {
    const cliEsbuildOptions = this.cliArgsToEsbuildOptions(args)
    this.esbuildConfig = { ...this.esbuildConfig, ...cliEsbuildOptions }
    return this
  }

  public convert() {
    this.esbuildConfig.entryPoints = this.transformEntryPoints()
    this.esbuildConfig.outdir = this.transformOutDir()
    this.esbuildConfig.sourcemap = this.transformSourcemap()
    this.esbuildConfig.target = this.transformTarget()
    this.esbuildConfig.format = this.transformFormat()
    return this.esbuildConfig
  }

  private cliArgsToEsbuildOptions(args: CliArgs): BuildOptions {
    const options: BuildOptions = {}
    if (args.watch) options.watch = true
    return options
  }

  private transformEntryPoints(): BuildOptions['entryPoints'] {
    return this.parsedCommandLine.fileNames
  }

  private transformOutDir(): BuildOptions['outdir'] {
    return this.parsedCommandLine.options.outDir || this.cwd // rootDir
  }

  private transformFormat(): BuildOptions['format'] {
    const explicit = this.parsedCommandLine.options?.module
    if (explicit !== undefined) {
      const moduleKey = ModuleKind[explicit]
      if (moduleKey === 'CommonJS') {
        return 'cjs'
      }
    }

    return 'esm'
  }

  private transformTarget(): BuildOptions['target'] {
    const explicit = this.parsedCommandLine.options?.target
    if (explicit) return [ScriptTarget[explicit].toLowerCase()]
    /**
     * tsc default to ES3
     * but esbuild do not support es3, we choose es6 for best compability.
     * https://esbuild.github.io/api/#target
     */
    return ['es2015']
  }

  private transformSourcemap(): BuildOptions['sourcemap'] {
    if (this.parsedCommandLine.options.inlineSourceMap) return 'inline'
    if (this.parsedCommandLine.options.sourceMap) return 'external'
    return undefined
  }
}