const fs = require('fs')
const path = require('path')
const chokidar = require('chokidar')
const assign_deep = require('assign-deep')

//const deepmerge = require('deepmerge')
// https://github.com/jonschlinkert/assign-deep // 类似 Object.assign 直接赋值到第一个对象里。只下载2个包。assign 优选。
// https://github.com/jonschlinkert/merge-deep // 生成一个新对象。会下载7～8个包。
// https://github.com/TehShrike/deepmerge // 生成一个新对象。只下载1个包。
// const deepmerge = require('@fastify/deepmerge')() // https://github.com/fastify/deepmerge // // 生成一个新对象。只下载1个包。assign优选。页面上有性能测试比较，超快。(他还有个 https://github.com/fastify/fast-json-stringify 也超快)

const my = { envar: {} }

module.exports = {
  start_watching ({ envarFiles = ['./envar-config.js', './envar-config.gitignore.js'], rawEnvar = {}, interval = 1000 } = {}) {
    chokidar.watch(envarFiles, { interval }).on('change', (onpath) => {
      // .on('all', (event, onpath)) 但这时，即使server刚启动，也会调用到这里一次
      globalThis.wo?.cclog?.('envarTool.start_watching: envar file changed:', onpath)
      try {
        // 或者调用 get_dynamic_envar。
        delete require.cache[require.resolve(path.resolve(onpath))]
        let newEnvar = require(path.resolve(onpath))
        if (typeof newEnvar === 'function') newEnvar = newEnvar()
        // 注意，assign_deep 会用 newEnvar 里的 undefined 属性覆盖掉 rawEnvar 里的原属性！所以要注意保持一致。（这和发送到前端的不一样，发送到前端的会被 JSON.stringify 以及 express 过滤掉 undefined.)
        // 目前的解决方案里，已通过 base2app 参数来确保只在发送给前端时才设置 undefined，但为防万一，在这里通过 JSON.stringify 确保删除了 undefined
        assign_deep(rawEnvar, JSON.parse(JSON.stringify(newEnvar)))
        globalThis.wo?.cclog?.(`envarTool.start_watching: OK reload ${onpath}`)
      } catch (expt) {
        globalThis.wo?.cclog?.(`envarTool.start_watching: Fail reload ${onpath}`)
        globalThis.wo?.ccerror?.(expt)
      }
    })
  },

  /** 合并 envar files 和 commander parameters 中的环境变量。
   * @param envarFiles:
   *  - 字符串: 导入文件，内容应当是字符串数组，或者对象。
   *  - 字符串数组: 按顺序导入导入每个文件，后面文件里的变量覆盖前面的。
   *  - 对象: 直接添加到 rawEnvar 上。
   */
  merge_envar ({ rawEnvar = {}, envarFiles = ['./envar-config.js', './envar-config.gitignore.js'] } = {}) {
    globalThis.wo?.ccinfo?.({ _from: 'merge_envar', about: `<<<<<<<< Configuring [${process.env.NODE_ENV}] Environment <<<<<<<<` })

    globalThis.wo?.ccinfo?.({ _from: 'merge_envar', about: '- Loading Configuration Files (读取配置文件)' })
    if (typeof envarFiles === 'string') {
      // 例如当输入参数为 envarFiles = 'envar-config.js' 里面应当 module.exports 一个数组
      if (fs.existsSync(path.resolve(envarFiles))) {
        envarFiles = require(path.resolve(envarFiles))
      } else {
        globalThis.wo?.ccwarn?.({ _from: 'merge_envar', about: `  - ${envarFiles} is missing.` })
        envarFiles = undefined
      }
    }

    if (Array.isArray(envarFiles)) {
      for (let configFile of envarFiles) {
        if (fs.existsSync(path.resolve(configFile))) {
          const fileContent = require(path.resolve(configFile))
          if (typeof fileContent === 'object') {
            assign_deep(rawEnvar, fileContent)
          } else if (typeof fileContent === 'function') {
            assign_deep(rawEnvar, fileContent())
          }
          globalThis.wo?.ccinfo?.({ _from: 'merge_envar', about: `  - ${configFile} is loaded.` })
        } else {
          globalThis.wo?.ccwarn?.({ _from: 'merge_envar', about: `  - ${configFile} is missing.` })
        }
      }
    } else if (typeof envarFiles === 'object') {
      assign_deep(rawEnvar, envarFiles)
    } else if (typeof envarFiles === 'function') {
      assign_deep(rawEnvar, envarFiles())
    } else {
      globalThis.wo?.ccwarn?.({ _from: 'merge_envar', about: `  - unrecognized envarFiles!` })
    }

    if (process.argv.length > 2 && Array.isArray(rawEnvar.commanderOptions)) {
      globalThis.wo?.ccinfo?.({ _from: 'merge_envar', about: '- Loading Command Line Parameters (载入命令行参数)' })
      const commander = require('commander')
      commander.version(rawEnvar.Base_Version || '0.0.1', '-v, --version') // 默认是 -V。如果要 -v，就要加 '-v --version'
      for (let [key, param, desc] of rawEnvar.commanderOptions || []) {
        commander.option(param, `${desc} Default = "${rawEnvar[key]}"`)
      }
      commander.parse(process.argv)
      // globalThis.wo?.cclog?.({_at:new Date().toJSON(),_from:'merge_envar', about: '- Merging Command Line Parameters into Configuration (把命令行参数值合并入配置)' },'\n,')
      for (let key in commander) {
        if (!/^_/.test(key) && typeof commander[key] === 'string') {
          // commander 自带了一批 _开头的属性，过滤掉
          rawEnvar[key] = commander[key]
        }
      }
      delete rawEnvar.commanderOptions
    }

    globalThis.wo?.cclog?.({ _from: 'merge_envar', about: `>>>>>>>> Configured [${process.env.NODE_ENV || 'development'}] Environment >>>>>>>>` }, '\n,')

    return rawEnvar
  },

  /* 读取动态配置文件中的环境变量。
   */
  get_dynamic_envar ({ dynamicEnvarFiles = ['./envar-config.js', './envar-config.gitignore.js'], base2app, _clientInfo } = {}) {
    // config file should be absolute or relative to the node process's dir.

    let dynamicEnvar = {}

    if (typeof dynamicEnvarFiles === 'string') {
      // a file containing more files
      if (fs.existsSync(path.resolve(dynamicEnvarFiles))) {
        dynamicEnvarFiles = require(path.resolve(dynamicEnvarFiles))
      } else {
        globalThis.wo?.ccwarn?.({ _from: 'get_dynamic_envar', about: `  - ${dynamicEnvarFiles} is missing.` })
        dynamicEnvarFiles = undefined
      }
    }

    if (Array.isArray(dynamicEnvarFiles)) {
      for (let dynamicFile of dynamicEnvarFiles) {
        if (fs.existsSync(path.resolve(dynamicFile))) {
          delete require.cache[require.resolve(path.resolve(dynamicFile))] // delete require.cache[fullpath] 不起作用，必须要加 require.resolve
          const fileContent = require(path.resolve(dynamicFile))
          if (typeof fileContent === 'object') {
            assign_deep(dynamicEnvar, fileContent)
          } else if (typeof fileContent === 'function') {
            assign_deep(dynamicEnvar, fileContent({ base2app, _clientInfo }))
          }
          globalThis.wo?.ccinfo?.({ _from: 'get_dynamic_envar', about: `  - ${dynamicFile} is parsed.` })
        } else {
          globalThis.wo?.ccwarn?.({ _from: 'get_dynamic_envar', about: `  - ${dynamicFile} is missing.` })
        }
      }
    } else if (typeof dynamicEnvarFiles === 'object') {
      dynamicEnvar = dynamicEnvarFiles
    } else if (typeof dynamicEnvarFiles === 'function') {
      dynamicEnvar = dynamicEnvarFiles()
    } else {
      globalThis.wo?.ccwarn?.({ _from: 'get_dynamic_envar', about: `  - unrecognized dynamicEnvarFiles!` })
    }

    return dynamicEnvar
  },

  /* 隐藏机密配置文件中的环境变量。
   * 需要输出当前环境变量时，必须调用本函数，避免机密信息被输出。
   */
  mask_secret_envar ({ rawEnvar, secretEnvarFiles = ['./envar-secret.js', './envar-secret.gitignore.js'] } = {}) {
    let envar = JSON.parse(JSON.stringify(rawEnvar)) // 复制一份，避免污染

    let secretEnvar = {}

    if (typeof secretEnvarFiles === 'string') {
      if (fs.existsSync(path.resolve(secretEnvarFiles))) {
        secretEnvarFiles = require(path.resolve(secretEnvarFiles))
      } else {
        globalThis.wo?.ccwarn?.({ _from: 'mask_secret_envar', about: `  - ${secretEnvarFiles} is missing.` })
        secretEnvarFiles = undefined
      }
    }

    globalThis.wo?.ccinfo?.({ _from: 'mask_secret_envar', about: `  - Parsing secretEnvarFiles...` })
    if (Array.isArray(secretEnvarFiles)) {
      for (let secretFile of secretEnvarFiles) {
        if (fs.existsSync(path.resolve(secretFile))) {
          const fileContent = require(path.resolve(secretFile))
          if (typeof fileContent === 'object') {
            assign_deep(secretEnvar, fileContent)
          } else if (typeof fileContent === 'function') {
            assign_deep(secretEnvar, fileContent())
          }
          globalThis.wo?.ccinfo?.({ _from: 'mask_secret_envar', about: `  - ${secretFile} is parsed.` })
        } else {
          globalThis.wo?.ccwarn?.({ _from: 'mask_secret_envar', about: `  - ${secretFile} is missing.` })
        }
      }
    } else if (typeof secretEnvarFiles === 'object') {
      secretEnvar = secretEnvarFiles
    } else if (typeof secretEnvarFiles === 'function') {
      dynamicEnvar = secretEnvarFiles()
    } else {
      globalThis.wo?.ccwarn?.({ _from: 'mask_secret_envar', about: `  - unrecognized secretEnvarFiles!` })
    }

    for (let key in secretEnvar) {
      envar[key] = '****** confidential ******'
    }

    return envar
  },

  // 预制方法
  envar_all ({ files = ['./envar-config.js', './envar-config.gitignore.js', './envar-secret.js', './envar-secret.gitignore.js'] } = {}) {
    let envar = this.get_envar({ inProcess: false, refresh: true, files })
    if (process.argv.length > 2 && Array.isArray(envar.commanderOptions)) {
      globalThis.wo?.ccinfo?.({ _from: 'envar_all', about: '- Loading Command Line Parameters (载入命令行参数)' })
      const commander = require('commander')
      commander.version(envar.Base_Version || '0.0.1', '-v, --version') // 默认是 -V。如果要 -v，就要加 '-v --version'
      for (let [key, param, desc] of envar.commanderOptions || []) {
        commander.option(param, `${desc} Default = "${envar[key]}"`)
      }
      commander.parse(process.argv)
      // globalThis.wo?.cclog?.({_at:new Date().toJSON(),_from:'envar_all', about: '- Merging Command Line Parameters into Configuration (把命令行参数值合并入配置)' },'\n,')
      for (let key in commander) {
        if (!/^_/.test(key) && typeof commander[key] === 'string') {
          // commander 自带了一批 _开头的属性，过滤掉
          envar[key] = commander[key]
        }
      }
      delete envar.commanderOptions
    }
    return envar
  },
  envar_basic ({ envarKey, files = ['./envar-config.js', './envar-config.gitignore.js'] } = {}) {
    return (my['basic'] = this.get_envar({ envarKey, inProcess: false, inCache: true, cachename: 'basic', refresh: false, files }))
  },
  envar_dynamic ({ envarKey, files = ['./envar-config.js', './envar-config.gitignore.js'] } = {}) {
    return this.get_envar({ envarKey, inProcess: true, inCache: false, refresh: true, files })
  },
  envar_sesame ({ envarKey, files = ['./envar-secret.js', './envar-secret.gitignore.js'] } = {}) {
    return (my['sesame'] = this.get_envar({ envarKey, inProcess: true, inCache: true, cachename: 'sesame', refresh: false, files }))
  },
  // 可定制的通用方法
  get_envar ({ envarKey, inProcess, inCache, cachename, files, refresh } = {}) {
    if (envarKey)
      return (
        (inProcess && process.env[envarKey]) ||
        (inCache && my[cachename || 'envar']?.[envarKey]) ||
        (files && this.merge_envar_files({ refresh, files })[envarKey])
      )
    else return (inCache && my[cachename || 'envar']) || (files && this.merge_envar_files({ refresh, files }))
  },
  merge_envar_files ({ refresh = false, files } = {}) {
    let envar = {}

    if (typeof files === 'string') {
      // a file containing more files
      if (fs.existsSync(path.resolve(files))) {
        files = require(path.resolve(files))
      } else {
        globalThis.wo?.ccwarn?.({ _from: 'merge_envar_files', about: `  - ${files} is missing.` })
        files = undefined
      }
    }

    if (Array.isArray(files)) {
      for (let envarFile of files) {
        if (fs.existsSync(path.resolve(envarFile))) {
          if (refresh) {
            delete require.cache[require.resolve(path.resolve(envarFile))] // delete require.cache[fullpath] 不起作用，必须要加 require.resolve
          }
          assign_deep(envar, require(path.resolve(envarFile)))
          globalThis.wo?.ccinfo?.({ _from: 'merge_envar_files', about: `  - ${envarFile} is parsed.` })
        } else {
          globalThis.wo?.ccwarn?.({ _from: 'merge_envar_files', about: `  - ${envarFile} is missing.` })
        }
      }
    } else if (typeof files === 'object') {
      envar = files
    } else {
      globalThis.wo?.ccwarn?.({ _from: 'merge_envar_files', about: `  - unrecognized files!` })
    }

    return envar
  },
}