/** Syntax highlighting for /bin/edit (line-oriented, best-effort). */

const EDIT_KW_JS =
  /^(?:const|let|var|function|return|async|await|if|else|for|while|do|switch|case|break|continue|default|try|catch|finally|throw|new|typeof|instanceof|in|of|class|extends|super|this|static|import|export|from|as|default|void|delete|yield|enum|interface|type|public|private|protected|readonly)$/

/**
 * @param {string} path
 */
function bareEditDetectLang(path) {
  const p = String(path || '').toLowerCase()
  const dot = p.lastIndexOf('.')
  const ext = dot >= 0 ? p.slice(dot) : ''
  if (ext === '.json') return 'json'
  if (ext === '.md' || ext === '.markdown') return 'md'
  if (ext === '.sh' || ext === '.bash' || ext === '.zsh') return 'shell'
  if (
    ext === '.js' ||
    ext === '.mjs' ||
    ext === '.cjs' ||
    ext === '.ts' ||
    ext === '.tsx' ||
    ext === '.jsx'
  )
    return 'js'
  return 'plain'
}

/**
 * Merge overlapping spans (later wins) — not used if we build non-overlapping.
 * @param {Array<{ start: number, end: number, cls: string }>} spans
 */
function bareEditMergeSpans(spans) {
  const s = spans.filter((x) => x.end > x.start).sort((a, b) => a.start - b.start || b.end - a.end)
  /** @type {typeof spans} */
  const out = []
  for (const cur of s) {
    const last = out[out.length - 1]
    if (!last || cur.start >= last.end) {
      out.push({ ...cur })
    } else if (cur.end > last.end) {
      if (cur.start > last.start) {
        out[out.length - 1] = { start: last.start, end: cur.start, cls: last.cls }
        out.push({ ...cur })
      } else {
        out[out.length - 1] = { ...cur }
      }
    }
  }
  return out
}

/**
 * @param {string} line
 * @returns {Array<{ start: number, end: number, cls: string }>}
 */
function bareEditSpansStringsCommentsJs(line) {
  /** @type {Array<{ start: number, end: number, cls: string }>} */
  const spans = []
  let i = 0
  while (i < line.length) {
    const c = line[i]
    const next = line[i + 1]
    if (c === '/' && next === '/') {
      spans.push({ start: i, end: line.length, cls: 'comment' })
      break
    }
    if (c === '/' && next === '*') {
      let j = i + 2
      while (j < line.length - 1) {
        if (line[j] === '*' && line[j + 1] === '/') {
          j += 2
          break
        }
        j++
      }
      if (j > line.length) j = line.length
      spans.push({ start: i, end: j, cls: 'comment' })
      i = j
      continue
    }
    if (c === '"' || c === "'" || c === '`') {
      const q = c
      const start = i
      i++
      while (i < line.length) {
        if (line[i] === '\\') {
          i += 2
          continue
        }
        if (line[i] === q) {
          i++
          break
        }
        i++
      }
      spans.push({ start, end: i, cls: 'string' })
      continue
    }
    i++
  }
  return bareEditMergeSpans(spans)
}

/**
 * @param {string} segment code only (no strings/comments inside)
 */
function bareEditSpansKeywordsNumbers(segment, offset) {
  /** @type {Array<{ start: number, end: number, cls: string }>} */
  const out = []
  const re = /\b([A-Za-z_$][\w$]*)\b|\b(\d+(?:\.\d+)?(?:[eE][+-]?\d+)?)\b/g
  let m
  while ((m = re.exec(segment)) !== null) {
    if (m[1]) {
      if (EDIT_KW_JS.test(m[1])) {
        out.push({
          start: offset + m.index,
          end: offset + m.index + m[1].length,
          cls: 'keyword'
        })
      }
    } else if (m[2]) {
      out.push({
        start: offset + m.index,
        end: offset + m.index + m[2].length,
        cls: 'number'
      })
    }
  }
  return out
}

/**
 * @param {string} line
 * @param {number} gapStart
 * @param {number} gapEnd
 * @param {Array<{ start: number, end: number, cls: string }>} base
 */
function bareEditFillGapKeywords(line, gapStart, gapEnd, base) {
  if (gapEnd <= gapStart) return
  const seg = line.slice(gapStart, gapEnd)
  const extra = bareEditSpansKeywordsNumbers(seg, gapStart)
  for (const e of extra) base.push(e)
}

/**
 * @param {string} line
 */
function bareEditHighlightJsLine(line) {
  const sc = bareEditSpansStringsCommentsJs(line)
  if (sc.length === 0) {
    const all = /** @type {typeof sc} */ ([])
    bareEditFillGapKeywords(line, 0, line.length, all)
    return all.sort((a, b) => a.start - b.start)
  }
  /** @type {typeof sc} */
  const out = [...sc]
  let cursor = 0
  for (const sp of sc) {
    bareEditFillGapKeywords(line, cursor, sp.start, out)
    cursor = sp.end
  }
  bareEditFillGapKeywords(line, cursor, line.length, out)
  return out.sort((a, b) => a.start - b.start)
}

/**
 * @param {string} line
 */
function bareEditHighlightJsonLine(line) {
  const t = line.trimStart()
  if (t.startsWith('//')) {
    return [{ start: line.indexOf('//'), end: line.length, cls: 'comment' }]
  }
  /** @type {Array<{ start: number, end: number, cls: string }>} */
  const spans = []
  const re = /("(?:\\.|[^"\\])*")\s*:|("(?:\\.|[^"\\])*")|(\btrue|false|null\b)|(-?\d+(?:\.\d+)?(?:[eE][+-]?\d+)?)/g
  let m
  while ((m = re.exec(line)) !== null) {
    if (m[1]) {
      const keyEnd = m.index + m[1].length
      spans.push({ start: m.index, end: keyEnd, cls: 'keyword' })
    } else if (m[2]) {
      spans.push({
        start: m.index,
        end: m.index + m[2].length,
        cls: 'string'
      })
    } else if (m[3]) {
      spans.push({
        start: m.index,
        end: m.index + m[3].length,
        cls: 'keyword'
      })
    } else if (m[4]) {
      spans.push({
        start: m.index,
        end: m.index + m[4].length,
        cls: 'number'
      })
    }
  }
  return spans.sort((a, b) => a.start - b.start)
}

/**
 * @param {string} line
 */
function bareEditHighlightShellLine(line) {
  const idx = line.indexOf('#')
  if (idx >= 0) {
    return [{ start: idx, end: line.length, cls: 'comment' }]
  }
  /** @type {Array<{ start: number, end: number, cls: string }>} */
  const spans = []
  const kw =
    /^\s*(if|then|else|elif|fi|for|while|do|done|case|esac|function|return|export|local|readonly|source|\.)[\s#;]|\b(if|then|else|elif|fi|for|in|do|done|case|esac|function|return|export|local|readonly)\b/g
  let m
  while ((m = kw.exec(line)) !== null) {
    const word = m[1] || m[2]
    if (!word) continue
    const start = m.index + m[0].indexOf(word)
    spans.push({ start, end: start + word.length, cls: 'keyword' })
  }
  const dq = /"(?:\\.|[^"\\])*"/g
  while ((m = dq.exec(line)) !== null) {
    spans.push({ start: m.index, end: m.index + m[0].length, cls: 'string' })
  }
  const sq = /'[^']*'/g
  while ((m = sq.exec(line)) !== null) {
    spans.push({ start: m.index, end: m.index + m[0].length, cls: 'string' })
  }
  return spans.sort((a, b) => a.start - b.start)
}

/**
 * @param {string} line
 */
function bareEditHighlightMdLine(line) {
  /** @type {Array<{ start: number, end: number, cls: string }>} */
  const spans = []
  if (/^\s*#{1,6}\s/.test(line)) {
    const m = line.match(/^\s*(#{1,6}\s.*)$/)
    if (m) {
      const i = line.indexOf(m[1])
      spans.push({ start: i, end: line.length, cls: 'keyword' })
    }
    return spans
  }
  if (/^\s*(?:[-*+]|\d+\.)\s/.test(line)) {
    const m = line.match(/^\s*((?:[-*+]|\d+\.)\s.*)$/)
    if (m) {
      const i = line.indexOf(m[1])
      spans.push({ start: i, end: line.length, cls: 'comment' })
    }
    return spans
  }
  const bold = /\*\*[^*]+\*\*|__[^_]+__/g
  let m
  while ((m = bold.exec(line)) !== null) {
    spans.push({ start: m.index, end: m.index + m[0].length, cls: 'string' })
  }
  const code = /`[^`]+`/g
  while ((m = code.exec(line)) !== null) {
    spans.push({ start: m.index, end: m.index + m[0].length, cls: 'number' })
  }
  return spans.sort((a, b) => a.start - b.start)
}

/**
 * @param {string} line
 * @param {string} lang
 */
function bareEditHighlightLine(line, lang) {
  switch (lang) {
    case 'js':
      return bareEditHighlightJsLine(line)
    case 'json':
      return bareEditHighlightJsonLine(line)
    case 'shell':
      return bareEditHighlightShellLine(line)
    case 'md':
      return bareEditHighlightMdLine(line)
    default:
      return []
  }
}