// Each command has a completion function that takes an options object and a cb The callback gets called with an error and an array of possible completions.
// The options object is built up based on the environment variables set by zsh or bash when calling a function for completion, based on the cursor position and the command line thus far.
// These are:
// COMP_CWORD: the index of the "word" in the command line being completed
// COMP_LINE: the full command line thus far as a string
// COMP_POINT: the cursor index at the point of triggering completion
//
// We parse the command line with nopt, like npm does, and then create an options object containing:
// words: array of words in the command line
// w: the index of the word being completed (ie, COMP_CWORD)
// word: the word being completed
// line: the COMP_LINE
// lineLength
// point: the COMP_POINT, usually equal to line length, but not always, eg if the user has pressed the left-arrow to complete an earlier word
// partialLine: the line up to the point
// partialWord: the word being completed (which might be ''), up to the point
// conf: a nopt parse of the command line
//
// When the implementation completion method returns its list of strings, and arrays of strings, we filter that by any that start with the partialWord, since only those can possibly be valid matches.
//
// Matches are wrapped with ' to escape them, if necessary, and then printed one per line for the shell completion method to consume in IFS=$'\n' mode as an array.

const fs = require('node:fs/promises')
const nopt = require('nopt')
const { resolve } = require('node:path')
const { output } = require('proc-log')
const Npm = require('../npm.js')
const { definitions, shorthands } = require('@npmcli/config/lib/definitions')
const { commands, aliases, deref } = require('../utils/cmd-list.js')
const { isWindowsShell } = require('../utils/is-windows.js')
const BaseCommand = require('../base-cmd.js')

const fileExists = (file) => fs.stat(file).then(s => s.isFile()).catch(() => false)

class Completion extends BaseCommand {
  static description = 'Tab Completion for npm'
  static name = 'completion'
  // Completion command uses args differently - they represent the command line being completed, not actual arguments to this command, so we use an empty definitions object to prevent flag validation
  static definitions = []
  static skipConfigValidation = true

  // completion for the completion command
  static async completion (opts) {
    if (opts.w > 2) {
      return
    }

    const [bashExists, zshExists] = await Promise.all([
      fileExists(resolve(process.env.HOME, '.bashrc')),
      fileExists(resolve(process.env.HOME, '.zshrc')),
    ])
    const out = []
    if (zshExists) {
      out.push(['>>', '~/.zshrc'])
    }

    if (bashExists) {
      out.push(['>>', '~/.bashrc'])
    }

    return out
  }

  async exec (args) {
    if (isWindowsShell) {
      const msg = 'npm completion supported only in MINGW / Git bash on Windows'
      throw Object.assign(new Error(msg), {
        code: 'ENOTSUP',
      })
    }

    const { COMP_CWORD, COMP_LINE, COMP_POINT, COMP_FISH } = process.env

    // if the COMP_* isn't in the env, then just dump the script.
    if (COMP_CWORD === undefined || COMP_LINE === undefined || COMP_POINT === undefined) {
      return dumpScript(resolve(this.npm.npmRoot, 'lib', 'utils', 'completion.sh'))
    }

    // ok we're actually looking at the envs and outputting the suggestions get the partial line and partial word, if the point isn't at the end.
    // ie, tabbing at: npm foo b|ar
    const w = +COMP_CWORD
    const line = COMP_LINE
    // Use COMP_LINE to get words if args doesn't include flags (e.g., in tests)
    const hasFlags = line.includes(' -') && !args.some(arg => arg.startsWith('-'))
    const words = (hasFlags ? line.split(/\s+/) : args).map(unescape)
    const word = words[w] || ''
    const point = +COMP_POINT
    const partialLine = line.slice(0, point)
    const partialWords = words.slice(0, w)

    // figure out where in that last word the point is.
    const partialWordRaw = args[w] || ''
    let i = partialWordRaw.length
    while (partialWordRaw.slice(0, i) !== partialLine.slice(-1 * i) && i > 0) {
      i--
    }

    const partialWord = unescape(partialWordRaw.slice(0, i))
    partialWords.push(partialWord)

    const opts = {
      isFish: COMP_FISH === 'true',
      words,
      w,
      word,
      line,
      lineLength: line.length,
      point,
      partialLine,
      partialWords,
      partialWord,
      raw: args,
    }

    // try to find the npm command and subcommand early for flag completion this helps with custom command definitions from subcommands
    const types = Object.entries(definitions).reduce((acc, [key, def]) => {
      acc[key] = def.type
      return acc
    }, {})
    const parsed = opts.conf =
      nopt(types, shorthands, partialWords.slice(0, -1), 0)
    const cmd = parsed.argv.remain[1]
    const subCmd = parsed.argv.remain[2]

    if (partialWords.slice(0, -1).indexOf('--') === -1) {
      if (word && word.charAt(0) === '-') {
        return this.wrap(opts, configCompl(opts, cmd, subCmd, this.npm))
      }

      if (words[w - 1] &&
        words[w - 1].charAt(0) === '-' &&
        !isFlag(words[w - 1], cmd, subCmd, this.npm)) {
        // awaiting a value for a non-bool config.
        // don't even try to do this for now
        return this.wrap(opts, configValueCompl(opts))
      }
    }

    // check if there's a command already.
    if (!cmd) {
      return this.wrap(opts, cmdCompl(opts, this.npm))
    }

    Object.keys(parsed).forEach(k => this.npm.config.set(k, parsed[k]))

    // at this point, if words[1] is some kind of npm command, then complete on it.
    // otherwise, do nothing
    try {
      const { completion } = Npm.cmd(cmd)
      if (completion) {
        const comps = await completion(opts, this.npm)
        return this.wrap(opts, comps)
      }
    } catch {
      // it wasn't a valid command, so do nothing
    }
  }

  // The command should respond with an array.
  // Loop over that, wrapping quotes around any that have spaces, and writing them to stdout.
  // If any of the items are arrays, then join them with a space.
  // e.g. returning ['a', 'b c', ['d', 'e']] would allow it to expand to: 'a', 'b c', or 'd' 'e'
  wrap (opts, compls) {
    if (opts.partialWord) {
      compls = compls.filter(c => c.startsWith(opts.partialWord))
    }

    if (compls.length > 0) {
      output.standard(compls.join('\n'))
    }
  }
}

const dumpScript = async (p) => {
  const d = (await fs.readFile(p, 'utf8')).replace(/^#!.*?\n/, '')
  await new Promise((res, rej) => {
    let done = false
    process.stdout.on('error', er => {
      if (done) {
        return
      }

      done = true

      // Darwin is a pain sometimes.
      //
      // This is necessary because the "source" or "." program in bash on OS X closes its file argument before reading from it, meaning that you get exactly 1 write, which will work most of the time, and will always raise an EPIPE.
      //
      // Really, one should not be tossing away EPIPE errors, or any errors, so casually.
      // But, without this, `. <(npm completion)` can never ever work on OS X.
      // TODO Ignoring coverage, see 'non EPIPE errors cause failures' test.
      /* istanbul ignore next */
      if (er.errno === 'EPIPE') {
        res()
      } else {
        rej(er)
      }
    })

    process.stdout.write(d, () => {
      if (done) {
        return
      }

      done = true
      res()
    })
  })
}

const unescape = w => w.charAt(0) === '\'' ? w.replace(/^'|'$/g, '')
  : w.replace(/\\ /g, ' ')

// Helper to get custom definitions from a command/subcommand
const getCustomDefinitions = (cmd, subCmd) => {
  if (!cmd) {
    return []
  }

  try {
    const command = Npm.cmd(cmd)

    // Check if the command has subcommands
    if (subCmd && command.subcommands && command.subcommands[subCmd]) {
      const subcommand = command.subcommands[subCmd]
      // All subcommands have definitions
      return subcommand.definitions
    }

    // Check if the command itself has definitions
    if (command.definitions) {
      return command.definitions
    }
  } catch {
    // Command not found or no definitions
  }

  return []
}

// Helper to get all config names including aliases from custom definitions
const getCustomConfigNames = (customDefs) => {
  const names = new Set()
  for (const def of customDefs) {
    names.add(def.key)
    if (def.alias && Array.isArray(def.alias)) {
      def.alias.forEach(a => names.add(a))
    }
  }
  return [...names]
}

// the current word has a dash.
// Return the config names with the same number of dashes as the current word has.
const configCompl = (opts, cmd, subCmd, npm) => {
  const word = opts.word
  const split = word.match(/^(-+)((?:no-)*)(.*)$/)
  const dashes = split[1]
  const no = split[2]

  // Get custom definitions from the command/subcommand
  const customDefs = getCustomDefinitions(cmd, subCmd, npm)
  const customNames = getCustomConfigNames(customDefs)

  // If there are custom definitions, return only those (new feature)
  // Otherwise, return empty array (historical behavior - no global flag completion)
  if (customNames.length > 0) {
    const flags = customNames.filter(name => isFlag(name, cmd, subCmd, npm))
    return customNames.map(c => dashes + c)
      .concat(flags.map(f => dashes + (no || 'no-') + f))
  }

  return []
}

// expand with the valid values of various config values.
// not yet implemented.
const configValueCompl = () => []

// check if the thing is a flag or not.
const isFlag = (word, cmd, subCmd, npm) => {
  // shorthands never take args.
  const split = word.match(/^(-*)((?:no-)+)?(.*)$/)
  const no = split[2]
  const conf = split[3]

  // Check custom definitions first
  const customDefs = getCustomDefinitions(cmd, subCmd, npm)

  // Check if conf is in custom definitions or is an alias
  let customDef = customDefs.find(d => d.key === conf)
  if (!customDef) {
    // Check if conf is an alias for any of the custom definitions
    for (const def of customDefs) {
      if (def.alias && Array.isArray(def.alias) && def.alias.includes(conf)) {
        customDef = def
        break
      }
    }
  }

  if (customDef) {
    const { type } = customDef
    return no ||
      type === Boolean ||
      (Array.isArray(type) && type.includes(Boolean))
  }

  // No custom definitions found, should not reach here in normal flow since configCompl returns empty array when no custom defs exist
  return false
}

// complete against the npm commands
// if they all resolve to the same thing, just return the thing it already is
const cmdCompl = (opts) => {
  const allCommands = commands.concat(Object.keys(aliases))
  const matches = allCommands.filter(c => c.startsWith(opts.partialWord))
  if (!matches.length) {
    return matches
  }

  const derefs = new Set([...matches.map(c => deref(c))])
  if (derefs.size === 1) {
    return [...derefs]
  }

  return allCommands
}

module.exports = Completion
