// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
//
// 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 ofdgo

import (
	"fmt"
	"math"
	"slices"
	"strconv"
	"strings"
)

// Box 矩形区域
type Box struct {
	X, Y, W, H float64
}

// Point 平面坐标点
type Point struct {
	X, Y float64
}

// ParseBox 解析Box字符串
// 入参: s 字符串
// 返回: Box 矩形对象, error 错误信息
func ParseBox(s string) (Box, error) {
	var values [4]float64
	i := 0
	for part := range strings.FieldsSeq(s) {
		if i == len(values) {
			return Box{}, fmt.Errorf("invalid box: %s", s)
		}
		value, err := strconv.ParseFloat(part, 64)
		if err != nil {
			return Box{}, fmt.Errorf("invalid box: %s", s)
		}
		values[i] = value
		i++
	}
	if i != len(values) {
		return Box{}, fmt.Errorf("invalid box: %s", s)
	}
	return Box{X: values[0], Y: values[1], W: values[2], H: values[3]}, nil
}

// Matrix 2D仿射变换矩阵
type Matrix struct {
	a, b, c, d, e, f float64
}

// IdentityMatrix 单位矩阵
var IdentityMatrix = Matrix{1, 0, 0, 1, 0, 0}

// NewMatrix 解析CTM字符串
// 入参: s 字符串
// 返回: Matrix 矩阵对象
func NewMatrix(s string) Matrix {
	floats := parseFloats(s)
	if len(floats) != 6 {
		return IdentityMatrix
	}
	return Matrix{
		a: floats[0], b: floats[1],
		c: floats[2], d: floats[3],
		e: floats[4], f: floats[5],
	}
}

// Multiply 矩阵乘法 (m * o)
// 入参: o 右侧矩阵
// 返回: Matrix 结果矩阵
func (m Matrix) Multiply(o Matrix) Matrix {
	return Matrix{
		a: m.a*o.a + m.c*o.b,
		b: m.b*o.a + m.d*o.b,
		c: m.a*o.c + m.c*o.d,
		d: m.b*o.c + m.d*o.d,
		e: m.a*o.e + m.c*o.f + m.e,
		f: m.b*o.e + m.d*o.f + m.f,
	}
}

// Transform 应用变换矩阵
// 入参: x X坐标, y Y坐标
// 返回: float64 变换后X, float64 变换后Y
func (m Matrix) Transform(x, y float64) (float64, float64) {
	nx := m.a*x + m.c*y + m.e
	ny := m.b*x + m.d*y + m.f
	return nx, ny
}

// TransformBox 获取矩形经仿射变换后的轴对齐边界
// 入参: box 原始矩形范围
// 返回: Box 变换后的轴对齐边界
func (m Matrix) TransformBox(box Box) Box {
	x, y := m.Transform(box.X, box.Y)
	left, top, right, bottom := x, y, x, y
	for _, point := range [][2]float64{{box.X + box.W, box.Y}, {box.X, box.Y + box.H}, {box.X + box.W, box.Y + box.H}} {
		x, y := m.Transform(point[0], point[1])
		left, top, right, bottom = math.Min(left, x), math.Min(top, y), math.Max(right, x), math.Max(bottom, y)
	}
	return Box{X: left, Y: top, W: right - left, H: bottom - top}
}

// String 返回标准CTM属性值
// 返回: string 六个空格分隔的矩阵分量
func (m Matrix) String() string {
	return fmt.Sprintf("%s %s %s %s %s %s", ofdNumber(m.a), ofdNumber(m.b), ofdNumber(m.c), ofdNumber(m.d), ofdNumber(m.e), ofdNumber(m.f))
}

// axisAlignedMatrix 判断变换是否保持坐标轴平行，含直角旋转与镜像
// 入参: m 仿射变换矩阵
// 返回: bool 是否为非退化的轴对齐变换
func axisAlignedMatrix(m Matrix) bool {
	return m.b == 0 && m.c == 0 && m.a != 0 && m.d != 0 || m.a == 0 && m.d == 0 && m.b != 0 && m.c != 0
}

// matrixVector 变换位移，不包含平移分量
// 入参: m 仿射变换矩阵, x、y 原始位移
// 返回: float64 变换后的X位移, float64 变换后的Y位移
func matrixVector(m Matrix, x, y float64) (float64, float64) {
	return m.a*x + m.c*y, m.b*x + m.d*y
}

// Invert 求逆矩阵
// 返回: Matrix 逆矩阵, bool 是否可逆
func (m Matrix) Invert() (Matrix, bool) {
	det := m.a*m.d - m.b*m.c
	if math.Abs(det) < 1e-9 {
		return IdentityMatrix, false
	}
	return Matrix{
		a: m.d / det,
		b: -m.b / det,
		c: -m.c / det,
		d: m.a / det,
		e: (m.c*m.f - m.d*m.e) / det,
		f: (m.b*m.e - m.a*m.f) / det,
	}, true
}

// TranslationMatrix 构造平移矩阵
// 入参: x X轴偏移, y Y轴偏移
// 返回: Matrix 平移矩阵
func TranslationMatrix(x, y float64) Matrix {
	return Matrix{a: 1, d: 1, e: x, f: y}
}

// YScale 获取Y轴缩放比例
// 返回: float64 缩放比例
func (m Matrix) YScale() float64 {
	return math.Sqrt(m.c*m.c + m.d*m.d)
}

// parseFloats 解析浮点数数组
// 入参: s 字符串
// 返回: []float64 浮点数数组
func parseFloats(s string) []float64 {
	if s == "" {
		return nil
	}
	if strings.Contains(s, "g") {
		return parseFloatsWithG(s)
	}
	s = strings.ReplaceAll(s, ",", " ")
	parts := strings.Fields(s)
	result := make([]float64, 0, len(parts))
	for _, p := range parts {
		if v, err := strconv.ParseFloat(p, 64); err == nil {
			result = append(result, v)
		}
	}
	return result
}

// parseFloatsWithG 解析带g的压缩浮点数数组
// 入参: s 字符串
// 返回: []float64 浮点数数组
func parseFloatsWithG(s string) []float64 {
	var result []float64
	gFlag := false
	gCount := 0
	for p := range strings.FieldsSeq(s) {
		if p == "g" {
			gFlag = true
			continue
		}
		if gFlag {
			var err error
			gCount, err = strconv.Atoi(p)
			if err != nil {
				gCount = 0
			}
			gFlag = false
			continue
		}
		if gCount > 0 {
			v, _ := strconv.ParseFloat(p, 64)
			result = slices.Grow(result, gCount)
			for j := 0; j < gCount; j++ {
				result = append(result, v)
			}
			gCount = 0
		} else {
			if v, err := strconv.ParseFloat(p, 64); err == nil {
				result = append(result, v)
			}
		}
	}
	return result
}

// parseInts 解析整数数组
// 入参: s 字符串
// 返回: []int 整数数组
func parseInts(s string) []int {
	if s == "" {
		return nil
	}
	s = strings.ReplaceAll(s, ",", " ")
	parts := strings.Fields(s)
	result := make([]int, 0, len(parts))
	for _, p := range parts {
		if v, err := strconv.Atoi(p); err == nil {
			result = append(result, v)
		}
	}
	return result
}