// Copyright 2020 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package axes

// label.go contains code that calculates the positions of labels on the axes.

import (
	"errors"
	"image"
)

// Label is one text label on an axis.
type Label struct {
	// Label content.
	Text string

	// Position of the label within the canvas.
	Pos image.Point
}

// yLabels returns labels that should be placed next to the cells.
// The labelWidth is the width of the area from the left-most side of the
// canvas until the Y axis (not including the Y axis). This is the area where
// the labels will be placed and aligned.
// Labels are returned with Y coordinates in ascending order.
// Y coordinates grow down.
func yLabels(graphHeight, labelWidth int, stringLabels []string) ([]*Label, error) {
	return nil, errors.New("not implemented")
}

// rowLabel returns one label for the specified row.
// The row is the Y coordinate of the row, Y coordinates grow down.
func rowLabel(row int, label string, labelWidth int) (*Label, error) {
	return nil, errors.New("not implemented")
}

// xLabels returns labels that should be placed under the cells.
// Labels are returned with X coordinates in ascending order.
// X coordinates grow right.
func xLabels(yEnd image.Point, graphWidth int, stringLabels []string, cellWidth int) ([]*Label, error) {
	return nil, errors.New("not implemented")
}

// paddedLabelLength calculates the length of the padded X label and
// the column index corresponding to the label.
// For example, the longest X label's length is 5, like '12:34', and the cell's width is 3.
// So in order to better display, every three columns of cells will display a X label,
// the X label belongs to the middle column of the three columns,
// and the padded length is 3*3 (cellWidth multiplies the number of columns), which is 9.
func paddedLabelLength(graphWidth, longest, cellWidth int) (l, index int) {
	return
}