package gofpdf

import (
	"fmt"
	"math"
)

// Routines in this file are translated from the work of Moritz Wagner and
// Andreas Würmser.

// The matrix used for generalized transformations of text, drawings and images.
type TransformMatrix struct {
	A, B, C, D, E, F float64
}

// Set up a transformation context for subsequent text, drawings and images.
// The typical usage is to immediately follow a call to this method with a call
// to one or more of the transformation methods such as TransformScale(),
// TransformSkew(), etc. This is followed by text, drawing or image output and
// finally a call to TransformEnd(). All transformation contexts must be
// properly ended prior to outputting the document.
//
// See tutorial 17 for transformation examples.
func (f *Fpdf) TransformBegin() {
	f.transformNest++
	f.out("q")
}

// Scale the width of the following text, drawings and images. scaleWd is the
// percentage scaling factor. (x, y) is center of scaling.
func (f *Fpdf) TransformScaleX(scaleWd, x, y float64) {
	f.TransformScale(scaleWd, 100, x, y)
}

// Scale the height of the following text, drawings and images. scaleHt is the
// percentage scaling factor. (x, y) is center of scaling.
func (f *Fpdf) TransformScaleY(scaleHt, x, y float64) {
	f.TransformScale(100, scaleHt, x, y)
}

// Uniformly scale the width and height of the following text, drawings and
// images. s is the percentage scaling factor for both width and height. (x, y)
// is center of scaling.
func (f *Fpdf) TransformScaleXY(s, x, y float64) {
	f.TransformScale(s, s, x, y)
}

// Generally scale the following text, drawings and images. scaleWd and scaleHt
// are the percentage scaling factors for width and height. (x, y) is center of
// scaling.
func (f *Fpdf) TransformScale(scaleWd, scaleHt, x, y float64) {
	if scaleWd == 0 || scaleHt == 0 {
		f.err = fmt.Errorf("Scale factor cannot be zero")
		return
	}
	y = (f.h - y) * f.k
	x *= f.k
	scaleWd /= 100
	scaleHt /= 100
	f.Transform(TransformMatrix{scaleWd, 0, 0,
		scaleHt, x * (1 - scaleWd), y * (1 - scaleHt)})
}

// Horizontally mirror the following text, drawings and images. x is the axis
// of reflection.
func (f *Fpdf) TransformMirrorHorizontal(x float64) {
	f.TransformScale(-100, 100, x, f.y)
}

// Vertically mirror the following text, drawings and images. y is the axis
// of reflection.
func (f *Fpdf) TransformMirrorVertical(y float64) {
	f.TransformScale(100, -100, f.x, y)
}

// Symmetrically mirror the following text, drawings and images on the point
// specified by (x, y).
func (f *Fpdf) TransformMirrorPoint(x, y float64) {
	f.TransformScale(-100, -100, x, y)
}

// Symmetrically mirror the following text, drawings and images on the line
// defined by angle and the point (x, y). angles is specified in degrees and
// measured counter-clockwise from the 3 o'clock position.
func (f *Fpdf) TransformMirrorLine(angle, x, y float64) {
	f.TransformScale(-100, 100, x, y)
	f.TransformRotate(-2*(angle-90), x, y)
}

// Move the following text, drawings and images horizontally by the amount
// specified by tx.
func (f *Fpdf) TransformTranslateX(tx float64) {
	f.TransformTranslate(tx, 0)
}

// Move the following text, drawings and images vertically by the amount
// specified by ty.
func (f *Fpdf) TransformTranslateY(ty float64) {
	f.TransformTranslate(0, ty)
}

// Move the following text, drawings and images horizontally and vertically by
// the amounts specified by tx and ty.
func (f *Fpdf) TransformTranslate(tx, ty float64) {
	f.Transform(TransformMatrix{1, 0, 0, 1, tx * f.k, -ty * f.k})
}

// Rotate the following text, drawings and images around the center point (x,
// y). angle is specified in degrees and measured counter-clockwise from the 3
// o'clock position.
func (f *Fpdf) TransformRotate(angle, x, y float64) {
	y = (f.h - y) * f.k
	x *= f.k
	angle = angle * math.Pi / 180
	var tm TransformMatrix
	tm.A = math.Cos(angle)
	tm.B = math.Sin(angle)
	tm.C = -tm.B
	tm.D = tm.A
	tm.E = x + tm.B*y - tm.A*x
	tm.F = y - tm.A*y - tm.B*x
	f.Transform(tm)
}

// Horizontally skew the following text, drawings and images keeping the point
// (x, y) stationary. angleX ranges from -90 degrees (skew to the left) to 90
// degrees (skew to the right).
func (f *Fpdf) TransformSkewX(angleX, x, y float64) {
	f.TransformSkew(angleX, 0, x, y)
}

// Vertically skew the following text, drawings and images keeping the point
// (x, y) stationary. angleY ranges from -90 degrees (skew to the bottom) to 90
// degrees (skew to the top).
func (f *Fpdf) TransformSkewY(angleY, x, y float64) {
	f.TransformSkew(0, angleY, x, y)
}

// Generally skew the following text, drawings and images keeping the point (x,
// y) stationary. angleX ranges from -90 degrees (skew to the left) to 90
// degrees (skew to the right). angleY ranges from -90 degrees (skew to the
// bottom) to 90 degrees (skew to the top).
func (f *Fpdf) TransformSkew(angleX, angleY, x, y float64) {
	if angleX <= -90 || angleX >= 90 || angleY <= -90 || angleY >= 90 {
		f.err = fmt.Errorf("Skew values must be between -90° and 90°")
		return
	}
	x *= f.k
	y = (f.h - y) * f.k
	var tm TransformMatrix
	tm.A = 1
	tm.B = math.Tan(angleY * math.Pi / 180)
	tm.C = math.Tan(angleX * math.Pi / 180)
	tm.D = 1
	tm.E = -tm.C * y
	tm.F = -tm.B * x
	f.Transform(tm)
}

// Generally transform the following text, drawings and images according to the
// specified matrix. It is typically easier to use the various methods such as
// TransformRotate() and TransformMirrorVertical() instead.
func (f *Fpdf) Transform(tm TransformMatrix) {
	if f.transformNest > 0 {
		f.outf("%.5f %.5f %.5f %.5f %.5f %.5f cm",
			tm.A, tm.B, tm.C, tm.D, tm.E, tm.F)
	} else if f.err == nil {
		f.err = fmt.Errorf("Transformation context is not active")
	}
}

// Apply a transformation that was begun with a call to TransformBegin().
func (f *Fpdf) TransformEnd() {
	if f.transformNest > 0 {
		f.transformNest--
		f.out("Q")
	} else {
		f.err = fmt.Errorf("Error attempting to end transformation operation out of sequence")
	}
}