import path from 'node:path'
import { isMatch } from 'picomatch'
import { glob } from 'tinyglobby'
import {
  type EnvironmentModuleNode,
  type Plugin,
  type ViteDevServer,
  loadConfigFromFile,
  normalizePath
} from 'vite'

const loaderMatch = /\.data\.m?(j|t)s($|\?)/

let server: ViteDevServer

export interface LoaderModule {
  watch?: string[] | string
  load: (watchedFiles: string[]) => any
}

/**
 * Helper for defining loaders with type inference
 */
export function defineLoader(loader: LoaderModule) {
  return loader
}

// Map from loader module id to its module info
const idToLoaderModulesMap: Record<string, LoaderModule | undefined> =
  Object.create(null)

// Map from dependency file to a set of loader module ids
const depToLoaderModuleIdsMap: Record<string, Set<string>> = Object.create(null)

// During build, the load hook will be called on the same file twice
// once for client and once for server build. Not only is this wasteful, it
// also leads to a race condition in loadConfigFromFile() that results in an
// fs unlink error. So we reuse the same Promise during build to avoid double
// loading.
let idToPendingPromiseMap: Record<string, Promise<string> | undefined> =
  Object.create(null)
let isBuild = false

export const staticDataPlugin: Plugin = {
  name: 'vitepress:data',

  configResolved(config) {
    isBuild = config.command === 'build'
  },

  configureServer(_server) {
    server = _server
  },

  async load(id) {
    if (loaderMatch.test(id)) {
      let _resolve: ((res: any) => void) | undefined
      if (isBuild) {
        if (idToPendingPromiseMap[id]) {
          return idToPendingPromiseMap[id]
        }
        idToPendingPromiseMap[id] = new Promise((r) => {
          _resolve = r
        })
      }

      const base = path.dirname(id)
      let watch: LoaderModule['watch']
      let load: LoaderModule['load']

      const existing = idToLoaderModulesMap[id]
      if (existing) {
        ;({ watch, load } = existing)
      } else {
        // use vite's load config util as a way to load Node.js file with
        // TS & native ESM support
        const res = await loadConfigFromFile({} as any, id.replace(/\?.*$/, ''))

        // record deps for hmr
        if (server && res) {
          for (const dep of res.dependencies) {
            const depPath = normalizePath(path.resolve(dep))
            if (!depToLoaderModuleIdsMap[depPath]) {
              depToLoaderModuleIdsMap[depPath] = new Set()
            }
            depToLoaderModuleIdsMap[depPath].add(id)
          }
        }

        const loaderModule = res?.config as LoaderModule
        watch =
          typeof loaderModule.watch === 'string'
            ? [loaderModule.watch]
            : loaderModule.watch
        if (watch) {
          watch = watch.map((p) => {
            return p.startsWith('.')
              ? normalizePath(path.resolve(base, p))
              : normalizePath(p)
          })
        }
        load = loaderModule.load
      }

      // load the data
      let watchedFiles: string[] = []
      if (watch) {
        watchedFiles = (
          await glob(watch, {
            ignore: ['**/node_modules/**', '**/dist/**'],
            expandDirectories: false
          })
        ).sort()
      }
      const data = await load(watchedFiles)

      // record loader module for HMR
      if (server) {
        idToLoaderModulesMap[id] = { watch, load }
      }

      const result = `export const data = JSON.parse(${JSON.stringify(JSON.stringify(data))})`

      if (_resolve) _resolve(result)
      return result
    }
  },

  hotUpdate({ file, modules: existingMods }) {
    if (this.environment.name !== 'client') return

    const modules: EnvironmentModuleNode[] = []
    const normalizedFile = normalizePath(file)

    // Trigger update if a dependency (including transitive ones) changed.
    if (normalizedFile in depToLoaderModuleIdsMap) {
      for (const id of Array.from(
        depToLoaderModuleIdsMap[normalizedFile] || []
      )) {
        delete idToLoaderModulesMap[id]
        const mod = this.environment.moduleGraph.getModuleById(id)
        if (mod) {
          modules.push(mod)
        }
      }
    }

    // Also check if the file matches any custom watch patterns.
    for (const id in idToLoaderModulesMap) {
      const loader = idToLoaderModulesMap[id]
      if (loader && loader.watch && isMatch(normalizedFile, loader.watch)) {
        const mod = this.environment.moduleGraph.getModuleById(id)
        if (mod && !modules.includes(mod)) {
          modules.push(mod)
        }
      }
    }

    return modules.length ? [...existingMods, ...modules] : undefined
  }
}