eval.go

// Copyright (c) 2021 Terminus, Inc.
//
// This program is free software: you can use, redistribute, and/or modify
// it under the terms of the GNU Affero General Public License, version 3
// or later ("AGPL"), as published by the Free Software Foundation.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.

package pexpr

import (
	"fmt"
	"strings"

	"gopkg.in/Knetic/govaluate.v3"

	"github.com/erda-project/erda/pkg/strutil"
)

// Eval 递归渲染统一表达式语法里的占位符，再计算表达式结果
// exprStr: 表达式
// placeholderParams: 占位符参数
func Eval(exprStr string, placeholderParams map[string]string) (interface{}, error) {
	// 校验表达式
	invalidPhs := FindInvalidPlaceholders(exprStr)
	if len(invalidPhs) > 0 {
		return nil, fmt.Errorf("invalid expression, found invalid placeholders: %s (must match: %s)", strings.Join(invalidPhs, ", "), PhRe.String())
	}

	// 递归渲染表达式中的占位符
	// 直到渲染完毕或找到不存在的占位符
	for {
		var notFoundPlaceholders []string
		exprStr = strutil.ReplaceAllStringSubmatchFunc(PhRe, exprStr, func(subs []string) string {
			ph := subs[0]    // ${{ configs.key }}
			inner := subs[1] // configs.key

			v, ok := placeholderParams[inner]
			if ok {
				return v
			}
			notFoundPlaceholders = append(notFoundPlaceholders, ph)
			return exprStr
		})
		if len(notFoundPlaceholders) > 0 {
			return nil, fmt.Errorf("invalid expression, not found placeholders: %s", strings.Join(notFoundPlaceholders, ", "))
		}
		// 没有需要替换的占位符，则退出渲染
		if !PhRe.MatchString(exprStr) {
			break
		}
	}

	// 计算表达式
	expr, err := govaluate.NewEvaluableExpression(exprStr)
	if err != nil {
		return nil, fmt.Errorf("invalid expression: %s, err: %v", exprStr, err)
	}
	strParams := make(map[string]interface{}, len(placeholderParams))
	for k, v := range placeholderParams {
		strParams[k] = v
	}
	result, err := expr.Evaluate(strParams)
	if err != nil {
		return nil, fmt.Errorf("failed to evaluate expr, expr: %s, err: %v", exprStr, err)
	}

	return result, nil
}