package gofpdf

import (
	"strconv"
)

func unused(args ...interface{}) {
}

// RGBType holds fields for red, green and blue color components
type RGBType struct {
	R, G, B int
}

// RGBAType holds fields for red, green and blue color components and an alpha
// transparency value
type RGBAType struct {
	R, G, B int
	Alpha   float64
}

// StateType holds various commonly used drawing values for convenient
// retrieval and restore methods
type StateType struct {
	clrDraw, clrText, clrFill RGBType
	lineWd                    float64
	fontSize                  float64
	alpha                     float64
	blendStr                  string
	cellMargin                float64
}

// StateGet returns a variable that contains common state values.
func StateGet(pdf *Fpdf) (st StateType) {
	st.clrDraw.R, st.clrDraw.G, st.clrDraw.B = pdf.GetDrawColor()
	st.clrFill.R, st.clrFill.G, st.clrFill.B = pdf.GetFillColor()
	st.clrText.R, st.clrText.G, st.clrText.B = pdf.GetTextColor()
	st.lineWd = pdf.GetLineWidth()
	_, st.fontSize = pdf.GetFontSize()
	st.alpha, st.blendStr = pdf.GetAlpha()
	st.cellMargin = pdf.GetCellMargin()
	return
}

// StatePut sets the common state values contained in the state structure
// specified by st.
func (st StateType) Put(pdf *Fpdf) {
	pdf.SetDrawColor(st.clrDraw.R, st.clrDraw.G, st.clrDraw.B)
	pdf.SetFillColor(st.clrFill.R, st.clrFill.G, st.clrFill.B)
	pdf.SetTextColor(st.clrText.R, st.clrText.G, st.clrText.B)
	pdf.SetLineWidth(st.lineWd)
	pdf.SetFontUnitSize(st.fontSize)
	pdf.SetAlpha(st.alpha, st.blendStr)
	pdf.SetCellMargin(st.cellMargin)
}

// TickFormatFncType defines a callback for label drawing.
type TickFormatFncType func(val float64, precision int) string

// defaultFormatter returns the string form of val with precision decimal places.
func defaultFormatter(val float64, precision int) string {
	return strconv.FormatFloat(val, 'f', precision, 64)
}

// GridType assists with the generation of graphs. It allows the application to
// work with logical data coordinates rather than page coordinates and assists
// with the drawing of a background grid.
type GridType struct {
	// Chart coordinates in page units
	x, y, w, h float64
	// X, Y, Wd, Ht float64
	// Slopes and intercepts scale data points to graph coordinates linearly
	xm, xb, ym, yb float64
	// Tickmarks
	xTicks, yTicks []float64
	// Formatters; use nil to eliminate labels
	XTickStr, YTickStr TickFormatFncType
	// Subdivisions between tickmarks
	XDiv, YDiv int
	// Formatting precision
	xPrecision, yPrecision int
	// Line and label colors
	ClrText, ClrMain, ClrSub RGBAType
	// Line thickness
	WdMain, WdSub float64
	// Label height in points
	TextSize float64
}

// linear returns the slope and y-intercept of the straight line joining the
// two specified points. For scaling purposes, associate the arguments as
// follows: x1: observed low value, y1: desired low value, x2: observed high
// value, y2: desired high value.
func linear(x1, y1, x2, y2 float64) (slope, intercept float64) {
	if x2 != x1 {
		slope = (y2 - y1) / (x2 - x1)
		intercept = y2 - x2*slope
	}
	return
}

// linearTickmark returns the slope and intercept that will linearly map data
// values (the range of which is specified by the tickmark slice tm) to page
// values (the range of which is specified by lo and hi).
func linearTickmark(tm []float64, lo, hi float64) (slope, intercept float64) {
	ln := len(tm)
	if ln > 0 {
		slope, intercept = linear(tm[0], lo, tm[ln-1], hi)
	}
	return
}

// NewGrid returns a variable of type GridType that is initialized to draw on a
// rectangle of width w and height h with the upper left corner positioned at
// point (x, y). The coordinates are in page units, that is, the same as those
// specified in New().
//
// The returned variable is initialized with a very simple default tickmark
// layout that ranges from 0 to 1 in both axes. Prior to calling Grid(), the
// application may establish a more suitable tickmark layout by calling the
// methods TickmarksContainX() and TickmarksContainY(). These methods bound the
// data range with appropriate boundaries and divisions. Alternatively, if the
// exact extent and divisions of the tickmark layout are known, the methods
// TickmarksExtentX() and TickmarksExtentY may be called instead.
func NewGrid(x, y, w, h float64) (grid GridType) {
	grid.x = x
	grid.y = y
	grid.w = w
	grid.h = h
	grid.TextSize = 7 // Points
	grid.TickmarksExtentX(0, 1, 1)
	grid.TickmarksExtentY(0, 1, 1)
	grid.XDiv = 10
	grid.YDiv = 10
	grid.ClrText = RGBAType{R: 0, G: 0, B: 0, Alpha: 1}
	grid.ClrMain = RGBAType{R: 128, G: 160, B: 128, Alpha: 1}
	grid.ClrSub = RGBAType{R: 192, G: 224, B: 192, Alpha: 1}
	grid.WdMain = 0.1
	grid.WdSub = 0.1
	grid.YTickStr = defaultFormatter
	grid.XTickStr = defaultFormatter
	return
}

// Wd converts dataWd, specified in logical data units, to the unit of measure
// specified in New().
func (g GridType) Wd(dataWd float64) float64 {
	return g.xm * dataWd
}

// X converts dataX, specified in logical data units, to the X position on the
// current page.
func (g GridType) X(dataX float64) float64 {
	return g.xm*dataX + g.xb
}

// Ht converts dataHt, specified in logical data units, to the unit of measure
// specified in New().
func (g GridType) Ht(dataHt float64) float64 {
	return g.ym * dataHt
}

// Y converts dataY, specified in logical data units, to the Y position on the
// current page.
func (g GridType) Y(dataY float64) float64 {
	return g.ym*dataY + g.yb
}

// TickmarksContainX sets the tickmarks to be shown by Grid() in the horizontal
// dimension. The argument min and max specify the minimum and maximum values
// to be contained within the grid. The tickmark values that are generated are
// suitable for general purpose graphs.
//
// See TickmarkExtentX() for an alternative to this method to be used when the
// exact values of the tickmarks are to be set by the application.
func (g *GridType) TickmarksContainX(min, max float64) {
	g.xTicks, g.xPrecision = Tickmarks(min, max)
	g.xm, g.xb = linearTickmark(g.xTicks, g.x, g.x+g.w)
}

// TickmarksContainY sets the tickmarks to be shown by Grid() in the vertical
// dimension. The argument min and max specify the minimum and maximum values
// to be contained within the grid. The tickmark values that are generated are
// suitable for general purpose graphs.
//
// See TickmarkExtentY() for an alternative to this method to be used when the
// exact values of the tickmarks are to be set by the application.
func (g *GridType) TickmarksContainY(min, max float64) {
	g.yTicks, g.yPrecision = Tickmarks(min, max)
	g.ym, g.yb = linearTickmark(g.yTicks, g.y+g.h, g.y)
}

func extent(min, div float64, count int) (tm []float64, precision int) {
	tm = make([]float64, count+1)
	for j := 0; j <= count; j++ {
		tm[j] = min
		min += div
	}
	precision = TickmarkPrecision(div)
	return
}

// TickmarksExtentX sets the tickmarks to be shown by Grid() in the horizontal
// dimension. count specifies number of major tickmark subdivisions to be
// graphed. min specifies the leftmost data value. div specifies, in data
// units, the extent of each major tickmark subdivision.
//
// See TickmarkContainX() for an alternative to this method to be used when
// viewer-friendly tickmarks are to be determined automatically.
func (g *GridType) TickmarksExtentX(min, div float64, count int) {
	g.xTicks, g.xPrecision = extent(min, div, count)
	g.xm, g.xb = linearTickmark(g.xTicks, g.x, g.x+g.w)
}

// TickmarksExtentY sets the tickmarks to be shown by Grid() in the vertical
// dimension. count specifies number of major tickmark subdivisions to be
// graphed. min specifies the bottommost data value. div specifies, in data
// units, the extent of each major tickmark subdivision.
//
// See TickmarkContainY() for an alternative to this method to be used when
// viewer-friendly tickmarks are to be determined automatically.
func (g *GridType) TickmarksExtentY(min, div float64, count int) {
	g.yTicks, g.yPrecision = extent(min, div, count)
	g.ym, g.yb = linearTickmark(g.yTicks, g.y+g.h, g.y)
}

// func (g *GridType) SetXExtent(dataLf, paperLf, dataRt, paperRt float64) {
// 	g.xm, g.xb = linear(dataLf, paperLf, dataRt, paperRt)
// }

// func (g *GridType) SetYExtent(dataTp, paperTp, dataBt, paperBt float64) {
// 	g.ym, g.yb = linear(dataTp, paperTp, dataBt, paperBt)
// }

func lineAttr(pdf *Fpdf, clr RGBAType, lineWd float64) {
	pdf.SetLineWidth(lineWd)
	pdf.SetAlpha(clr.Alpha, "Normal")
	pdf.SetDrawColor(clr.R, clr.G, clr.B)
}

// Grid generates a graph-paperlike set of grid lines on the current page.
func (g GridType) Grid(pdf *Fpdf) {
	var st StateType
	// const textSz = 8
	// var halfTextSz = g.TextSize / 2
	var yLen, xLen int
	var textSz, halfTextSz, yMin, yMax, xMin, xMax, yDiv, xDiv float64
	var str string
	var strOfs, strWd, tp, bt, lf, rt, drawX, drawY float64

	textSz = pdf.PointToUnitConvert(g.TextSize)
	halfTextSz = textSz / 2
	strOfs = pdf.GetStringWidth("I")
	unused(strOfs)

	xLen = len(g.xTicks)
	yLen = len(g.yTicks)
	if xLen > 1 && yLen > 1 {

		st = StateGet(pdf)

		line := func(x1, y1, x2, y2 float64, heavy bool) {
			if heavy {
				lineAttr(pdf, g.ClrMain, g.WdMain)
			} else {
				lineAttr(pdf, g.ClrSub, g.WdSub)
			}
			pdf.Line(x1, y1, x2, y2)
		}

		pdf.SetAutoPageBreak(false, 0)
		pdf.SetFontUnitSize(textSz)
		pdf.SetFillColor(255, 255, 255)
		pdf.SetCellMargin(0)

		xMin = g.xTicks[0]
		xMax = g.xTicks[xLen-1]

		yMin = g.yTicks[0]
		yMax = g.yTicks[yLen-1]

		lf = g.X(xMin)
		rt = g.X(xMax)
		bt = g.Y(yMin)
		tp = g.Y(yMax)

		// Verticals along X axis
		xDiv = g.xTicks[1] - g.xTicks[0]
		if g.XDiv > 0 {
			xDiv = xDiv / float64(g.XDiv)
		}
		xDiv = g.Wd(xDiv)
		for j, x := range g.xTicks {
			drawX = g.X(x)
			line(drawX, tp, drawX, bt, true)
			if j < xLen-1 {
				for k := 1; k < g.XDiv; k++ {
					drawX += xDiv
					line(drawX, tp, drawX, bt, false)
				}
			}
		}

		// Horizontals along Y axis
		yDiv = g.yTicks[1] - g.yTicks[0]
		if g.YDiv > 0 {
			yDiv = yDiv / float64(g.YDiv)
		}
		yDiv = g.Ht(yDiv)
		for j, y := range g.yTicks {
			drawY = g.Y(y)
			line(lf, drawY, rt, drawY, true)
			if j < yLen-1 {
				for k := 1; k < g.YDiv; k++ {
					drawY += yDiv
					line(lf, drawY, rt, drawY, false)
				}
			}
		}

		// X labels
		if g.XTickStr != nil {
			drawY = bt // g.Y(yMin)
			for _, x := range g.xTicks {
				str = g.XTickStr(x, g.xPrecision) // strconv.FormatFloat(x, 'f', g.xPrecision, 64)
				strWd = pdf.GetStringWidth(str)
				drawX = g.X(x)
				pdf.TransformBegin()
				pdf.TransformRotate(90, drawX, drawY)
				pdf.SetXY(drawX+strOfs, drawY-halfTextSz)
				pdf.CellFormat(strWd, textSz, str, "", 0, "L", true, 0, "")
				pdf.TransformEnd()
			}
		}

		// Y labels
		if g.YTickStr != nil {
			drawX = lf + strOfs // g.X(xMin) + strOfs
			for _, y := range g.yTicks {
				// str = strconv.FormatFloat(y, 'f', g.yPrecision, 64)
				str = g.YTickStr(y, g.yPrecision)
				strWd = pdf.GetStringWidth(str)
				pdf.SetXY(drawX, g.Y(y)-halfTextSz)
				pdf.CellFormat(strWd, textSz, str, "", 0, "L", true, 0, "")
			}
		}

		// Restore drawing attributes
		st.Put(pdf)

	}

}

// Plot plots a series of count line segments from xMin to xMax. It repeatedly
// calls fnc(x) to retrieve the y value associate with x. The currently
// selected line drawing attributes are used.
func (g GridType) Plot(pdf *Fpdf, xMin, xMax float64, count int, fnc func(x float64) (y float64)) {
	if count > 0 {
		var x, delta, drawX0, drawY0, drawX1, drawY1 float64
		delta = (xMax - xMin) / float64(count)
		x = xMin
		for j := 0; j <= count; j++ {
			if j == 0 {
				drawX1 = g.X(x)
				drawY1 = g.Y(fnc(x))
			} else {
				pdf.Line(drawX0, drawY0, drawX1, drawY1)
			}
			x += delta
			drawX0 = drawX1
			drawY0 = drawY1
			drawX1 = g.X(x)
			drawY1 = g.Y(fnc(x))
		}
	}
}