acedoc/delta.go

package acedoc

import (
	"fmt"
	"strings"
)

/* ***** BEGIN LICENSE BLOCK *****
*
* Original license for JS algorithm, which has been rewritten in Go:
*
* Distributed under the BSD license:
*
* Copyright (c) 2010, Ajax.org B.V.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*     * Redistributions of source code must retain the above copyright
*       notice, this list of conditions and the following disclaimer.
*     * Redistributions in binary form must reproduce the above copyright
*       notice, this list of conditions and the following disclaimer in the
*       documentation and/or other materials provided with the distribution.
*     * Neither the name of Ajax.org B.V. nor the
*       names of its contributors may be used to endorse or promote products
*       derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL AJAX.ORG B.V. BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* ***** END LICENSE BLOCK ***** */

type DeltaAction bool

const (
	DeltaInsert DeltaAction = true
	DeltaRemove DeltaAction = false
)

type Delta struct {
	Action     DeltaAction
	Lines      []string
	Start, End Position
}

func Remove(row, col uint, str string) Delta {
	lines := strings.Split(str, "\n")
	nlines := len(lines) - 1
	return Delta{
		Action: DeltaRemove,
		Lines:  lines,
		Start:  Position{row, col},
		End:    Position{row + uint(nlines), uint(len(lines[nlines]))},
	}
}

func Insert(row, col uint, str string) Delta {
	lines := strings.Split(str, "\n")
	nlines := uint(len(lines) - 1)
	return Delta{
		Action: DeltaInsert,
		Lines:  lines,
		Start:  Position{row, col},
		End:    Position{row + nlines, uint(len(lines[nlines]))},
	}
}

func (d *Document) applyInsert(dl Delta) error {

	row := dl.Start.Row
	col := dl.Start.Column
	line := d.Lines[row]

	if dl.NLines() == 1 {
		d.Lines[row] = line[:col] + dl.Line(0) + line[col:]
	} else {
		newlines := []string{}
		if row != 0 {
			newlines = append(newlines, d.Lines[:row-1]...) // old content
		}
		newlines = append(newlines, d.Lines[row][:col]+dl.Lines[0])
		newlines = append(newlines, dl.Lines[1:]...) // new content
		newlines[len(newlines)-1] += d.Lines[row][col:]
		if uint(len(d.Lines)) > row {
			newlines = append(newlines, d.Lines[row+1:]...) // old content
		}
		d.Lines = newlines
	}

	return nil
}

func (d *Document) applyRemove(dl Delta) error {
	row := dl.Start.Row
	col := dl.Start.Column
	line := d.Lines[row]
	endCol := dl.End.Column
	endRow := dl.End.Row

	if row == endRow {
		d.Lines[row] = line[:col] + line[endCol:]
	} else {
		d.Lines[endRow] = d.Lines[row][:col] + d.Lines[endRow][endCol:]
		newlines := []string{}
		newlines = append(newlines, d.Lines[:row]...)
		newlines = append(newlines, d.Lines[endRow:]...)
		d.Lines = newlines
	}

	return nil
}

func (d *Document) Apply(dl Delta) error {
	d.mtx.Lock()
	defer d.mtx.Unlock()

	err := d.validate(dl)
	if err != nil {
		return fmt.Errorf("delta does not apply to document: %v", err)
	}

	switch dl.Action {
	case DeltaInsert:
		return d.applyInsert(dl)
	case DeltaRemove:
		return d.applyRemove(dl)
	}

	return nil
}

func (d *Document) validate(dl Delta) error {
	if !d.InDocument(dl.Start) {
		return fmt.Errorf("start is not in document")
	}

	if dl.Action == DeltaRemove && !d.InDocument(dl.End) {
		return fmt.Errorf("end is not in document for remove")
	}

	if dl.NLines() != dl.NRows() {
		return fmt.Errorf("delta has %d lines, but positions show range of %d lines", dl.NLines(), dl.NRows())
	}

	lastDlLine := dl.Line(dl.NRows() - 1)

	if uint(len(lastDlLine)) != dl.Cols() {
		return fmt.Errorf("delta has %d chars on the final line, but positions show range of %d chars", len(lastDlLine), dl.Cols())
	}

	return nil
}