// Copyright 2016 - 2019 The excelize Authors. All rights reserved. Use of
// this source code is governed by a BSD-style license that can be found in
// the LICENSE file.
//
// Package excelize providing a set of functions that allow you to write to
// and read from XLSX files. Support reads and writes XLSX file generated by
// Microsoft Excel™ 2007 and later. Support save file without losing original
// charts of XLSX. This library needs Go version 1.10 or later.

package excelize

import "strings"

// GetMergeCells provides a function to get all merged cells from a worksheet
// currently.
func (f *File) GetMergeCells(sheet string) ([]MergeCell, error) {
	var mergeCells []MergeCell
	xlsx, err := f.workSheetReader(sheet)
	if err != nil {
		return mergeCells, err
	}
	if xlsx.MergeCells != nil {
		mergeCells = make([]MergeCell, 0, len(xlsx.MergeCells.Cells))

		for i := range xlsx.MergeCells.Cells {
			ref := xlsx.MergeCells.Cells[i].Ref
			axis := strings.Split(ref, ":")[0]
			val, _ := f.GetCellValue(sheet, axis)
			mergeCells = append(mergeCells, []string{ref, val})
		}
	}

	return mergeCells, err
}

// UnmergeCell provides a function to unmerge a given coordinate area.
// For example unmerge area D3:E9 on Sheet1:
//
//    err := f.UnmergeCell("Sheet1", "D3", "E9")
//
// Attention: overlapped areas will also be unmerged.
func (f *File) UnmergeCell(sheet string, hcell, vcell string) error {
	xlsx, err := f.workSheetReader(sheet)
	if err != nil {
		return err
	}
	coordinates, err := f.areaRefToCoordinates(hcell + ":" + vcell)
	if err != nil {
		return err
	}
	x1, y1, x2, y2 := coordinates[0], coordinates[1], coordinates[2], coordinates[3]

	if x2 < x1 {
		x1, x2 = x2, x1
	}
	if y2 < y1 {
		y1, y2 = y2, y1
	}
	hcell, _ = CoordinatesToCellName(x1, y1)
	vcell, _ = CoordinatesToCellName(x2, y2)

	// return nil since no MergeCells in the sheet
	if xlsx.MergeCells == nil {
		return nil
	}

	ref := hcell + ":" + vcell
	i := 0
	for _, cellData := range xlsx.MergeCells.Cells {
		cc := strings.Split(cellData.Ref, ":")
		c1, _ := checkCellInArea(hcell, cellData.Ref)
		c2, _ := checkCellInArea(vcell, cellData.Ref)
		c3, _ := checkCellInArea(cc[0], ref)
		c4, _ := checkCellInArea(cc[1], ref)
		// skip the overlapped mergecell
		if c1 || c2 || c3 || c4 {
			continue
		}
		xlsx.MergeCells.Cells[i] = cellData
		i++
	}
	xlsx.MergeCells.Cells = xlsx.MergeCells.Cells[:i]
	return nil
}

// MergeCell define a merged cell data.
// It consists of the following structure.
// example: []string{"D4:E10", "cell value"}
type MergeCell []string

// GetCellValue returns merged cell value.
func (m *MergeCell) GetCellValue() string {
	return (*m)[1]
}

// GetStartAxis returns the merge start axis.
// example: "C2"
func (m *MergeCell) GetStartAxis() string {
	axis := strings.Split((*m)[0], ":")
	return axis[0]
}

// GetEndAxis returns the merge end axis.
// example: "D4"
func (m *MergeCell) GetEndAxis() string {
	axis := strings.Split((*m)[0], ":")
	return axis[1]
}