package common_calc

import (
	"errors"
	"fmt"
	"log"
	"math"
	"strconv"
	"strings"
	"unicode"
)

func CalculateFormula(formulaExpression string) float64 {
	//log.Printf("计算 %s\n", formulaExpression)
	formulaExpression = strings.Replace(formulaExpression, " ", "", -1)
	postfix, err := infix2ToPostfix(formulaExpression)
	if err != nil {
		log.Printf("计算异常[%s]=>%s", err.Error(), formulaExpression)
		return -255
	}
	return calculatePostfix(postfix)
}

func calculatePostfix(postfix []string) float64 {
	stack := Stack{}
	fixLen := len(postfix)
	for i := 0; i < fixLen; i++ {
		nextChar := postfix[i]
		// 数字：直接压栈

		if _, err := strconv.ParseFloat(nextChar, 64); err == nil {
			stack.Push(nextChar)
		} else {
			if nextChar == "π" {
				stack.Push(fmt.Sprintf("%v", math.Pi))
			} else {

				switch nextChar {
				case "sin":
					// 操作符：取出数字计算值，再将结果压栈
					num1, _ := strconv.ParseFloat(stack.Pop(), 64)
					stack.Push(fmt.Sprintf("%v", math.Sin(num1)))
				case "cos":
					// 操作符：取出数字计算值，再将结果压栈
					num1, _ := strconv.ParseFloat(stack.Pop(), 64)
					stack.Push(fmt.Sprintf("%v", math.Cos(num1)))
				case "√":
					// 操作符：取出数字计算值，再将结果压栈
					num1, _ := strconv.ParseFloat(stack.Pop(), 64)
					stack.Push(fmt.Sprintf("%v", math.Sqrt(num1)))
				case "²":
					// 操作符：取出数字计算值，再将结果压栈
					num1, _ := strconv.ParseFloat(stack.Pop(), 64)
					stack.Push(fmt.Sprintf("%v", math.Pow(num1, 2)))
				case "³":
					// 操作符：取出数字计算值，再将结果压栈
					num1, _ := strconv.ParseFloat(stack.Pop(), 64)
					stack.Push(fmt.Sprintf("%v", math.Pow(num1, 3)))
				case "+":
					// 操作符：取出两个数字计算值，再将结果压栈
					num1, _ := strconv.ParseFloat(stack.Pop(), 64)
					num2, _ := strconv.ParseFloat(stack.Pop(), 64)
					stack.Push(fmt.Sprintf("%v", num2+num1))
				case "-":
					num1, _ := strconv.ParseFloat(stack.Pop(), 64)
					num2, _ := strconv.ParseFloat(stack.Pop(), 64)
					stack.Push(fmt.Sprintf("%v", num2-num1))
				case "*":
					num1, _ := strconv.ParseFloat(stack.Pop(), 64)
					num2, _ := strconv.ParseFloat(stack.Pop(), 64)
					stack.Push(fmt.Sprintf("%v", num2*num1))
				case "/":
					num1, _ := strconv.ParseFloat(stack.Pop(), 64)
					num2, _ := strconv.ParseFloat(stack.Pop(), 64)
					stack.Push(fmt.Sprintf("%v", num2/num1))
				case "^":
					// 操作符：取出两个数字计算值，再将结果压栈
					num2, _ := strconv.ParseFloat(stack.Pop(), 64)
					num1, _ := strconv.ParseFloat(stack.Pop(), 64)
					stack.Push(fmt.Sprintf("%v", math.Pow(num1, num2)))
				}
			}
		}
	}
	result, _ := strconv.ParseFloat(stack.Top(), 64)
	return result
}

// 中缀表达式转后缀表达式
func infix2ToPostfix(expStr string) ([]string, error) {
	stack := Stack{}
	postfix := make([]string, 0)

	//-1.1-2 => 0-1.1-2
	//-1.1*2+1 => 0-1.1*2+1
	if strings.HasPrefix(expStr, "-") {
		expStr = fmt.Sprintf("0%s", expStr)
	}

	exp := []rune(expStr)
	expLen := len(exp)

	// 遍历整个表达式
	itemStr := ""
	for i := 0; i < expLen; i++ {

		char := string(exp[i])
		itemStr += char

		switch itemStr {
		case " ":
			continue
		case "[":
			// 左括号直接入栈
			stack.Push("[")
		case "]":
			// 右括号则弹出元素直到遇到左括号
			for !stack.IsEmpty() {
				preChar := stack.Top()
				if preChar == "[" {
					stack.Pop() // 弹出 "("
					break
				}
				postfix = append(postfix, preChar)
				stack.Pop()
			}

		case "(":
			// 左括号直接入栈
			stack.Push("(")
		case ")":
			// 右括号则弹出元素直到遇到左括号
			for !stack.IsEmpty() {
				preChar := stack.Top()
				if preChar == "(" {
					stack.Pop() // 弹出 "("
					break
				}
				postfix = append(postfix, preChar)
				stack.Pop()
			}
		case "π":
			postfix = append(postfix, "π")
			// 数字则直接输出
		case "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", ".":
			j := i
			digit := ""
			for ; j < expLen && (unicode.IsDigit(exp[j]) || "." == string(exp[j])); j++ {
				digit += string(exp[j])
			}

			postfix = append(postfix, digit)

			//支持 如2π这种写法
			if j < expLen && "π" == string(exp[j]) {
				postfix = append(postfix, "π", "*")
				j++
			}

			i = j - 1 // i 向前跨越一个整数，由于执行了一步多余的 j++，需要减 1

		default:
			//非操作符继续 拼接  用以支持多字符操作符如sin , cos
			if isOp := isOperator(itemStr); !isOp {
				if i+1 == expLen || len(itemStr) > 5 {
					return postfix, errors.New(fmt.Sprintf("不支持的无效的公式片段 %s", itemStr))
				}

				if unicode.IsDigit(exp[i+1]) {
					return postfix, errors.New(fmt.Sprintf("不支持的操作符 %s", itemStr))
				}

				continue
			}
			// 操作符：遇到高优先级的运算符，不断弹出，直到遇见更低优先级运算符
			for !stack.IsEmpty() {
				top := stack.Top()
				if (top == "(" || top == "[") || isLower(top, itemStr) {
					break
				}
				postfix = append(postfix, top)
				stack.Pop()
			}
			// 低优先级的运算符入栈
			stack.Push(itemStr)
		}
		itemStr = ""
	}

	// 栈不空则全部输出
	for !stack.IsEmpty() {
		postfix = append(postfix, stack.Pop())
	}

	return postfix, nil
}

// (12.3+0.1)*2.0+2
// 12.30.1+2.0*2+
// 后缀式计算
var operatorMap = []string{"√", "²", "³", "+", "-", "*", "/", "sin", "cos", "^"}

// 优先级定义
var operatorPriority = map[string]uint16{
	"+":   0,
	"-":   0,
	"*":   1,
	"/":   1,
	"√":   2,
	"^":   6,
	"sin": 7,
	"cos": 7,
	"²":   8,
	"³":   8,
	"[":   9,
	"(":   10,
}

func isOperator(op string) bool {
	for _, s := range operatorMap {
		if op == s {
			return true
		}
	}
	return false
}

// 比较运算符栈栈顶 top 和新运算符 newTop 的优先级高低
func isLower(top string, newTop string) bool {
	// 注意 a + b + c 的后缀表达式是 ab + c +，不是 abc + +

	Priority := operatorPriority[newTop] > operatorPriority[top]

	return Priority

	//switch top {
	//case "+", "-":
	//	if newTop == "*" || newTop == "/" {
	//		return true
	//	}
	//case "(":
	//	return true
	//}
	//return false
}

type Stack struct {
	data [100]string
	top  int
}

func (s *Stack) Push(d string) {
	s.data[s.top] = d
	s.top++
}

func (s *Stack) Pop() (d string) {
	if s.top == 0 {
		//err = fmt.Errorf("stack is empty")
	}
	s.top--
	d = s.data[s.top]
	return
}

func (s *Stack) Top() (d string) {
	if s.top == 0 {
		//err = fmt.Errorf("stack is empty")
	}
	d = s.data[s.top-1]
	return
}

func (s *Stack) IsEmpty() bool {
	return s.top == 0
}