#!/usr/bin/env node
import fs from 'fs/promises'
import path from 'path'

function usage() {
  console.log(`Usage:
  node scripts/count_column.js --file <file.csv> --column <columnName|index> [--out <out.txt>]

Options:
  --file     CSV 文件路径（必需）。
  --column   指定列名或列序号（1 表示第一列）。如果为数字则按 1-based 处理。
  --out      可选，将统计结果写入指定文件（默认：打印到控制台）。
  --help     显示帮助。
`)
}

function parseArgs(argv) {
  const args = argv.slice(2)
  const opts = { file: null, column: null, out: null }
  for (let i = 0; i < args.length; i++) {
    const a = args[i]
    if (a === '--help' || a === '-h') { opts.help = true; break }
    if (a === '--file') { opts.file = args[++i]; continue }
    if (a === '--column') { opts.column = args[++i]; continue }
    if (a === '--out') { opts.out = args[++i]; continue }
    // positional file
    if (!opts.file) opts.file = a
  }
  return opts
}

// 重用一个简单的 CSV 单行解析（支持双引号与双引号转义）
function parseCSVLine(line) {
  const res = []
  let cur = ''
  let inQuotes = false
  for (let i = 0; i < line.length; i++) {
    const ch = line[i]
    if (inQuotes) {
      if (ch === '"') {
        if (i + 1 < line.length && line[i + 1] === '"') { cur += '"'; i++ } else { inQuotes = false }
      } else { cur += ch }
    } else {
      if (ch === ',') { res.push(cur); cur = '' }
      else if (ch === '"') { inQuotes = true }
      else { cur += ch }
    }
  }
  res.push(cur)
  return res
}

async function readCSV(filePath) {
  const txt = await fs.readFile(filePath, 'utf8')
  const lines = txt.split(/\r?\n/)
  let headerLineIndex = null
  for (let i = 0; i < lines.length; i++) { if (lines[i].trim().length > 0) { headerLineIndex = i; break } }
  if (headerLineIndex === null) return { headers: [], rows: [] }
  const headers = parseCSVLine(lines[headerLineIndex])
  const rows = []
  for (let i = headerLineIndex + 1; i < lines.length; i++) {
    const l = lines[i]
    if (l == null || l.trim() === '') continue
    const vals = parseCSVLine(l)
    rows.push(vals)
  }
  return { headers, rows }
}

function normalizeKey(k) {
  if (k == null) return ''
  return String(k).trim()
}

async function main() {
  const opts = parseArgs(process.argv)
  if (opts.help) { usage(); return }
  if (!opts.file || !opts.column) { console.error('Missing --file or --column'); usage(); process.exit(1) }

  const filePath = path.isAbsolute(opts.file) ? opts.file : path.join(process.cwd(), opts.file)
  let stat
  try { stat = await fs.stat(filePath) } catch (e) { console.error('File not found:', filePath); process.exit(2) }
  if (!stat.isFile()) { console.error('Not a file:', filePath); process.exit(3) }

  const { headers, rows } = await readCSV(filePath)
  if (!headers || headers.length === 0) { console.error('No header found in CSV'); process.exit(4) }

  // 决定列索引：如果 opts.column 是纯数字则按 1-based 处理，否则按列名匹配（优先精确匹配，其次大小写忽略）
  let colIndex = -1
  if (/^\d+$/.test(opts.column)) {
    const idx = parseInt(opts.column, 10)
    colIndex = idx - 1
    if (colIndex < 0 || colIndex >= headers.length) { console.error('Column index out of range'); process.exit(5) }
  } else {
    // 尝试精确匹配
    colIndex = headers.indexOf(opts.column)
    if (colIndex === -1) {
      // 尝试不区分大小写匹配
      const lower = opts.column.toLowerCase()
      colIndex = headers.findIndex(h => String(h).toLowerCase() === lower)
      if (colIndex === -1) { console.error(`Column name not found: ${opts.column}`); process.exit(6) }
    }
  }

  const counts = new Map()
  for (const vals of rows) {
    const v = normalizeKey(vals[colIndex])
    counts.set(v, (counts.get(v) || 0) + 1)
  }

  // 排序：按计数降序，再按值字母升序
  const items = Array.from(counts.entries()).sort((a, b) => {
    if (b[1] !== a[1]) return b[1] - a[1]
    return String(a[0]).localeCompare(String(b[0]))
  })

  const outLines = []
  outLines.push(`File: ${filePath}`)
  outLines.push(`Column: ${headers[colIndex]} (index ${colIndex + 1})`)
  outLines.push(`Total distinct classes: ${items.length}`)
  outLines.push('')
  outLines.push('Value,Count')
  for (const [val, cnt] of items) outLines.push(`${val},${cnt}`)

  if (opts.out) {
    const outPath = path.isAbsolute(opts.out) ? opts.out : path.join(process.cwd(), opts.out)
    await fs.mkdir(path.dirname(outPath), { recursive: true })
    await fs.writeFile(outPath, outLines.join('\n'), 'utf8')
    console.log(`Wrote counts to ${outPath} (${items.length} distinct)`)
  } else {
    console.log(outLines.join('\n'))
  }
}

main().catch(err => { console.error('Error:', err && err.stack ? err.stack : err); process.exit(10) })