import transaction from beancount file

pkg/converters/beancount/beancount_amount_expression_evaluator.go

@@ -0,0 +1,197 @@
+package beancount
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/mayswind/ezbookkeeping/pkg/core"
+	"github.com/mayswind/ezbookkeeping/pkg/errs"
+	"github.com/mayswind/ezbookkeeping/pkg/log"
+)
+
+var operatorPriority = map[rune]int{
+	'+': 1,
+	'-': 1,
+	'*': 2,
+	'/': 2,
+}
+
+func toPostfixExprTokens(ctx core.Context, expr string) ([]string, error) {
+	finalTokens := make([]string, 0)
+	operatorStack := make([]rune, 0)
+	currentNumberBuilder := strings.Builder{}
+	isLastTokenOperator := true
+
+	expr = strings.ReplaceAll(expr, " ", "")
+
+	for i := 0; i < len(expr); i++ {
+		ch := rune(expr[i])
+
+		// number
+		if '0' <= ch && ch <= '9' || ch == '.' {
+			currentNumberBuilder.WriteRune(ch)
+			continue
+		} else if ch == '-' && i+1 < len(expr) && '0' <= expr[i+1] && expr[i+1] <= '9' && currentNumberBuilder.Len() == 0 && isLastTokenOperator {
+			currentNumberBuilder.WriteRune(ch)
+			continue
+		}
+
+		// operator or parenthesis
+		if currentNumberBuilder.Len() > 0 {
+			finalTokens = append(finalTokens, currentNumberBuilder.String())
+			currentNumberBuilder.Reset()
+			isLastTokenOperator = false
+		}
+
+		switch ch {
+		case '+', '-', '*', '/':
+			if ch == '-' && isLastTokenOperator {
+				currentNumberBuilder.WriteRune(ch)
+				continue
+			}
+
+			for len(operatorStack) > 0 {
+				topOperator := operatorStack[len(operatorStack)-1]
+
+				if topOperator == '(' {
+					break
+				}
+
+				if operatorPriority[topOperator] >= operatorPriority[ch] {
+					finalTokens = append(finalTokens, string(topOperator))
+					operatorStack = operatorStack[:len(operatorStack)-1]
+				} else {
+					break
+				}
+			}
+
+			operatorStack = append(operatorStack, ch)
+			isLastTokenOperator = true
+		case '(':
+			operatorStack = append(operatorStack, ch)
+			isLastTokenOperator = true
+		case ')':
+			hasLeftParenthesis := false
+
+			for len(operatorStack) > 0 {
+				topOperator := operatorStack[len(operatorStack)-1]
+				operatorStack = operatorStack[:len(operatorStack)-1]
+
+				if topOperator == '(' {
+					hasLeftParenthesis = true
+					break
+				}
+
+				finalTokens = append(finalTokens, string(topOperator))
+			}
+
+			if !hasLeftParenthesis {
+				log.Warnf(ctx, "[beancount_amount_expression_evaluator.toPostfixExprTokens] cannot parse expression \"%s\", because missing left parenthesis", expr)
+				return nil, errs.ErrInvalidAmountExpression
+			}
+
+			isLastTokenOperator = false
+		default:
+			log.Warnf(ctx, "[beancount_amount_expression_evaluator.toPostfixExprTokens] cannot parse expression \"%s\", because containing unknown token \"%c\"", expr, ch)
+			return nil, errs.ErrInvalidAmountExpression
+		}
+	}
+
+	if currentNumberBuilder.Len() > 0 {
+		finalTokens = append(finalTokens, currentNumberBuilder.String())
+	}
+
+	for len(operatorStack) > 0 {
+		topOperator := operatorStack[len(operatorStack)-1]
+		operatorStack = operatorStack[:len(operatorStack)-1]
+
+		if topOperator == '(' {
+			log.Warnf(ctx, "[beancount_amount_expression_evaluator.toPostfixExprTokens] cannot parse expression \"%s\", because missing right parenthesis", expr)
+			return nil, errs.ErrInvalidAmountExpression
+		}
+
+		finalTokens = append(finalTokens, string(topOperator))
+	}
+
+	return finalTokens, nil
+}
+
+func evaluatePostfixExpr(ctx core.Context, tokens []string) (float64, error) {
+	stack := make([]float64, 0)
+
+	for i := 0; i < len(tokens); i++ {
+		token := tokens[i]
+
+		switch token {
+		case "+", "-", "*", "/": // operators
+			if len(stack) < 2 {
+				log.Warnf(ctx, "[beancount_amount_expression_evaluator.evaluatePostfixExpr] cannot evaluate expression \"%s\", because not enough operands", strings.Join(tokens, " "))
+				return 0, errs.ErrInvalidAmountExpression
+			}
+
+			// pop the top two operands
+			b := stack[len(stack)-1]
+			stack = stack[:len(stack)-1]
+
+			a := stack[len(stack)-1]
+			stack = stack[:len(stack)-1]
+
+			// evaluate the operation
+			var result float64
+			switch token {
+			case "+":
+				result = a + b
+			case "-":
+				result = a - b
+			case "*":
+				result = a * b
+			case "/":
+				if b == 0 {
+					log.Warnf(ctx, "[beancount_amount_expression_evaluator.evaluatePostfixExpr] cannot evaluate expression \"%s\", because division by zero", strings.Join(tokens, " "))
+					return 0, errs.ErrInvalidAmountExpression
+				}
+				result = a / b
+			}
+
+			// push the result back to the stack
+			stack = append(stack, result)
+		default: // operands
+			num, err := strconv.ParseFloat(token, 64)
+
+			if err != nil {
+				log.Warnf(ctx, "[beancount_amount_expression_evaluator.evaluatePostfixExpr] cannot evaluate expression \"%s\", because containing invalid number", strings.Join(tokens, " "))
+				return 0, errs.ErrInvalidAmountExpression
+			}
+
+			stack = append(stack, num)
+		}
+	}
+
+	if len(stack) != 1 {
+		log.Warnf(ctx, "[beancount_amount_expression_evaluator.evaluatePostfixExpr] cannot evaluate expression \"%s\", because missing operator", strings.Join(tokens, " "))
+		return 0, errs.ErrInvalidAmountExpression
+	}
+
+	return stack[0], nil
+}
+
+func evaluateBeancountAmountExpression(ctx core.Context, expr string) (string, error) {
+	if expr == "" {
+		return "", nil
+	}
+
+	postfixExprTokens, err := toPostfixExprTokens(ctx, expr)
+
+	if err != nil {
+		return "", err
+	}
+
+	result, err := evaluatePostfixExpr(ctx, postfixExprTokens)
+
+	if err != nil {
+		return "", err
+	}
+
+	return fmt.Sprintf("%.2f", result), nil
+}