efritz/ij

package environment

import (
    "fmt"
    "os"
)

const ExpandMaxIterations = 50

func (e Environment) ExpandString(template string) (string, error) {
    return e.expandString(template, ExpandMaxIterations)
}

func (e Environment) ExpandSlice(templates []string) ([]string, error) {
    expanded := []string{}
    for _, template := range templates {
        val, err := e.ExpandString(template)
        if err != nil {
            return nil, err
        }

        expanded = append(expanded, val)
    }

    return expanded, nil
}

//
//

func (e Environment) expandString(template string, count int) (string, error) {
    if count == 0 {
        return "", fmt.Errorf(
            "failed to expand environment: current template is `%s`",
            template,
        )
    }

    if expanded := os.Expand(template, e.translate); expanded != template {
        return e.expandString(expanded, count-1)
    }

    return template, nil
}

func (e Environment) translate(name string) string {
    if name == "" {
        return "$"
    }

    if value, ok := e[name]; ok {
        return value
    }

    return fmt.Sprintf("${%s}", name)
}