package tmpl

import (
	"fmt"
	"gopkg.in/yaml.v2"
	"os"
	"path/filepath"
	"strings"
	"text/template"
)

type Values = map[string]interface{}

func (c *Context) createFuncMap() template.FuncMap {
	return template.FuncMap{
		"readFile":       c.ReadFile,
		"toYaml":         ToYaml,
		"fromYaml":       FromYaml,
		"setValueAtPath": SetValueAtPath,
		"requiredEnv":    RequiredEnv,
	}
}

func (c *Context) ReadFile(filename string) (string, error) {
	path := filepath.Join(c.basePath, filename)

	bytes, err := c.readFile(path)
	if err != nil {
		return "", err
	}
	return string(bytes), nil
}

func ToYaml(v interface{}) (string, error) {
	data, err := yaml.Marshal(v)
	if err != nil {
		return "", err
	}
	return string(data), nil
}

func FromYaml(str string) (Values, error) {
	m := Values{}

	if err := yaml.Unmarshal([]byte(str), &m); err != nil {
		return nil, err
	}
	return m, nil
}

func SetValueAtPath(path string, value interface{}, values Values) (Values, error) {
	var current interface{}
	current = values
	components := strings.Split(path, ".")
	pathToMap := components[:len(components)-1]
	key := components[len(components)-1]
	for _, k := range pathToMap {
		var elem interface{}

		switch typedCurrent := current.(type) {
		case map[string]interface{}:
			v, exists := typedCurrent[k]
			if !exists {
				return nil, fmt.Errorf("failed to set value at path \"%s\": value for key \"%s\" does not exist", path, k)
			}
			elem = v
		case map[interface{}]interface{}:
			v, exists := typedCurrent[k]
			if !exists {
				return nil, fmt.Errorf("failed to set value at path \"%s\": value for key \"%s\" does not exist", path, k)
			}
			elem = v
		default:
			return nil, fmt.Errorf("failed to set value at path \"%s\": value for key \"%s\" was not a map", path, k)
		}

		switch typedElem := elem.(type) {
		case map[string]interface{}, map[interface{}]interface{}:
			current = typedElem
		default:
			return nil, fmt.Errorf("failed to set value at path \"%s\": value for key \"%s\" was not a map", path, k)
		}
	}

	switch typedCurrent := current.(type) {
	case map[string]interface{}:
		typedCurrent[key] = value
	case map[interface{}]interface{}:
		typedCurrent[key] = value
	default:
		return nil, fmt.Errorf("failed to set value at path \"%s\": value for key \"%s\" was not a map", path, key)
	}
	return values, nil
}

func RequiredEnv(name string) (string, error) {
	if val, exists := os.LookupEnv(name); exists && len(val) > 0 {
		return val, nil
	}

	return "", fmt.Errorf("required env var `%s` is not set", name)
}