/** Text buffer + cursor + undo for /bin/edit. */

const EDIT_UNDO_MAX = 200

/**
 * @param {string} text
 */
function bareEditCreateBuffer(text) {
  const lines =
    text === '' ? [''] : String(text).replace(/\r\n/g, '\n').replace(/\r/g, '\n').split('\n')
  return {
    lines,
    row: 0,
    col: 0,
    dirty: false,
    /** @type {{ lines: string[], row: number, col: number }[]} */
    undo: [],
    /** @type {{ lines: string[], row: number, col: number }[]} */
    redo: []
  }
}

/**
 * @param {{ lines: string[], row: number, col: number, dirty: boolean, undo: unknown[], redo: unknown[] }} buf
 */
function bareEditSnapshot(buf) {
  return {
    lines: buf.lines.slice(),
    row: buf.row,
    col: buf.col
  }
}

/**
 * @param {{ lines: string[], row: number, col: number, dirty: boolean, undo: unknown[], redo: unknown[] }} buf
 */
function bareEditPushUndo(buf) {
  buf.undo.push(bareEditSnapshot(buf))
  if (buf.undo.length > EDIT_UNDO_MAX) buf.undo.shift()
  buf.redo = []
}

/**
 * @param {{ lines: string[], row: number, col: number, dirty: boolean, undo: unknown[], redo: unknown[] }} buf
 */
function bareEditUndo(buf) {
  const prev = buf.undo.pop()
  if (!prev) return false
  buf.redo.push(bareEditSnapshot(buf))
  buf.lines = /** @type {{ lines: string[] }} */ (prev).lines.slice()
  buf.row = prev.row
  buf.col = prev.col
  buf.dirty = true
  return true
}

/**
 * @param {{ lines: string[], row: number, col: number, dirty: boolean, undo: unknown[], redo: unknown[] }} buf
 */
function bareEditRedo(buf) {
  const next = buf.redo.pop()
  if (!next) return false
  buf.undo.push(bareEditSnapshot(buf))
  buf.lines = /** @type {{ lines: string[] }} */ (next).lines.slice()
  buf.row = next.row
  buf.col = next.col
  buf.dirty = true
  return true
}

/**
 * @param {{ lines: string[], row: number, col: number, dirty: boolean, undo: unknown[], redo: unknown[] }} buf
 */
function bareEditClampCursor(buf) {
  if (buf.row < 0) buf.row = 0
  if (buf.row >= buf.lines.length) buf.row = buf.lines.length - 1
  const line = buf.lines[buf.row] || ''
  if (buf.col < 0) buf.col = 0
  if (buf.col > line.length) buf.col = line.length
}

/**
 * @param {{ lines: string[], row: number, col: number, dirty: boolean, undo: unknown[], redo: unknown[] }} buf
 * @param {string} ch single code unit (MVP)
 */
function bareEditInsertChar(buf, ch) {
  bareEditPushUndo(buf)
  const line = buf.lines[buf.row]
  buf.lines[buf.row] = line.slice(0, buf.col) + ch + line.slice(buf.col)
  buf.col += ch.length
  buf.dirty = true
}

/**
 * @param {{ lines: string[], row: number, col: number, dirty: boolean, undo: unknown[], redo: unknown[] }} buf
 */
function bareEditNewline(buf) {
  bareEditPushUndo(buf)
  const line = buf.lines[buf.row]
  const rest = line.slice(buf.col)
  buf.lines[buf.row] = line.slice(0, buf.col)
  buf.lines.splice(buf.row + 1, 0, rest)
  buf.row++
  buf.col = 0
  buf.dirty = true
}

/**
 * Insert pasted text as one undo step (normalized newlines; tab → two spaces).
 * @param {{ lines: string[], row: number, col: number, dirty: boolean, undo: unknown[], redo: unknown[] }} buf
 * @param {string} text
 */
function bareEditInsertPasteText(buf, text) {
  const normalized = String(text).replace(/\r\n/g, '\n').replace(/\r/g, '\n')
  if (!normalized) return
  bareEditPushUndo(buf)
  for (const ch of normalized) {
    if (ch === '\n') {
      const line = buf.lines[buf.row]
      const rest = line.slice(buf.col)
      buf.lines[buf.row] = line.slice(0, buf.col)
      buf.lines.splice(buf.row + 1, 0, rest)
      buf.row++
      buf.col = 0
    } else if (ch === '\t') {
      const line = buf.lines[buf.row]
      buf.lines[buf.row] = line.slice(0, buf.col) + '  ' + line.slice(buf.col)
      buf.col += 2
    } else {
      const line = buf.lines[buf.row]
      buf.lines[buf.row] = line.slice(0, buf.col) + ch + line.slice(buf.col)
      buf.col += ch.length
    }
  }
  buf.dirty = true
  bareEditClampCursor(buf)
}

/**
 * @param {{ lines: string[], row: number, col: number, dirty: boolean, undo: unknown[], redo: unknown[] }} buf
 */
function bareEditBackspace(buf) {
  if (buf.col > 0) {
    bareEditPushUndo(buf)
    const line = buf.lines[buf.row]
    buf.lines[buf.row] = line.slice(0, buf.col - 1) + line.slice(buf.col)
    buf.col--
    buf.dirty = true
    return
  }
  if (buf.row > 0) {
    bareEditPushUndo(buf)
    const prevLen = buf.lines[buf.row - 1].length
    buf.lines[buf.row - 1] += buf.lines[buf.row]
    buf.lines.splice(buf.row, 1)
    buf.row--
    buf.col = prevLen
    buf.dirty = true
  }
}

/**
 * @param {{ lines: string[], row: number, col: number, dirty: boolean, undo: unknown[], redo: unknown[] }} buf
 */
function bareEditDelete(buf) {
  const line = buf.lines[buf.row]
  if (buf.col < line.length) {
    bareEditPushUndo(buf)
    buf.lines[buf.row] = line.slice(0, buf.col) + line.slice(buf.col + 1)
    buf.dirty = true
    return
  }
  if (buf.row < buf.lines.length - 1) {
    bareEditPushUndo(buf)
    buf.lines[buf.row] += buf.lines[buf.row + 1]
    buf.lines.splice(buf.row + 1, 1)
    buf.dirty = true
  }
}

/**
 * @param {{ lines: string[], row: number, col: number, dirty: boolean, undo: unknown[], redo: unknown[] }} buf
 * @param {'home'|'end'|'up'|'down'|'left'|'right'} key
 */
function bareEditMoveKey(buf, key) {
  if (key === 'home') {
    buf.col = 0
    return
  }
  if (key === 'end') {
    buf.col = buf.lines[buf.row].length
    return
  }
  if (key === 'up') {
    if (buf.row > 0) {
      buf.row--
      buf.col = Math.min(buf.col, buf.lines[buf.row].length)
    }
    return
  }
  if (key === 'down') {
    if (buf.row < buf.lines.length - 1) {
      buf.row++
      buf.col = Math.min(buf.col, buf.lines[buf.row].length)
    }
    return
  }
  if (key === 'left') {
    if (buf.col > 0) buf.col--
    else if (buf.row > 0) {
      buf.row--
      buf.col = buf.lines[buf.row].length
    }
    return
  }
  if (key === 'right') {
    const line = buf.lines[buf.row]
    if (buf.col < line.length) buf.col++
    else if (buf.row < buf.lines.length - 1) {
      buf.row++
      buf.col = 0
    }
  }
}

/**
 * @param {{ lines: string[], row: number, col: number, dirty: boolean, undo: unknown[], redo: unknown[] }} buf
 */
function bareEditJoinAll(buf) {
  return buf.lines.join('\n')
}

/**
 * @param {{ lines: string[], row: number, col: number, dirty: boolean, undo: unknown[], redo: unknown[] }} buf
 * @param {string} needle
 * @param {number} fromRow
 * @param {number} fromCol
 * @returns {{ row: number, col: number } | null}
 */
function bareEditFindNext(buf, needle, fromRow, fromCol) {
  if (!needle) return null
  for (let r = fromRow; r < buf.lines.length; r++) {
    const line = buf.lines[r] || ''
    const start = r === fromRow ? fromCol : 0
    const idx = line.indexOf(needle, start)
    if (idx >= 0) return { row: r, col: idx }
  }
  for (let r = 0; r < fromRow; r++) {
    const idx = (buf.lines[r] || '').indexOf(needle)
    if (idx >= 0) return { row: r, col: idx }
  }
  const line = buf.lines[fromRow] || ''
  const idx = line.indexOf(needle, 0)
  if (idx >= 0 && idx < fromCol) return { row: fromRow, col: idx }
  return null
}

/**
 * @param {{ lines: string[], row: number, col: number }} buf
 * @param {number} targetRow 1-based
 */
function bareEditGotoLine(buf, targetRow) {
  const r = Math.max(1, Math.min(buf.lines.length, targetRow)) - 1
  buf.row = r
  buf.col = Math.min(buf.col, buf.lines[r].length)
}