/*
Copyright 2017 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package env

import (
	"bufio"
	"fmt"
	"io"
	"os"
	"regexp"
	"strings"

	"k8s.io/apimachinery/pkg/util/sets"
	"k8s.io/kubernetes/pkg/api"
)

// Env returns an environment variable or a default value if not specified.
func Env(key string, defaultValue string) string {
	val := os.Getenv(key)
	if len(val) == 0 {
		return defaultValue
	}
	return val
}

// GetEnv returns an environment value if specified
func GetEnv(key string) (string, bool) {
	val := os.Getenv(key)
	if len(val) == 0 {
		return "", false
	}
	return val, true
}

var argumentEnvironment = regexp.MustCompile("(?ms)^(.+)\\=(.*)$")
var validArgumentEnvironment = regexp.MustCompile("(?ms)^(\\w+)\\=(.*)$")

// IsEnvironmentArgument check str is env args
func IsEnvironmentArgument(s string) bool {
	return argumentEnvironment.MatchString(s)
}

// IsValidEnvironmentArgument check str is valid env
func IsValidEnvironmentArgument(s string) bool {
	return validArgumentEnvironment.MatchString(s)
}

// SplitEnvironmentFromResources returns resources and envargs
func SplitEnvironmentFromResources(args []string) (resources, envArgs []string, ok bool) {
	first := true
	for _, s := range args {
		// this method also has to understand env removal syntax, i.e. KEY-
		isEnv := IsEnvironmentArgument(s) || strings.HasSuffix(s, "-")
		switch {
		case first && isEnv:
			first = false
			fallthrough
		case !first && isEnv:
			envArgs = append(envArgs, s)
		case first && !isEnv:
			resources = append(resources, s)
		case !first && !isEnv:
			return nil, nil, false
		}
	}
	return resources, envArgs, true
}

// parseIntoEnvVar parses the list of key-value pairs into kubernetes EnvVar.
// envVarType is for making errors more specific to user intentions.
func parseIntoEnvVar(spec []string, defaultReader io.Reader, envVarType string) ([]api.EnvVar, []string, error) {
	env := []api.EnvVar{}
	exists := sets.NewString()
	var remove []string
	for _, envSpec := range spec {
		switch {
		case !IsValidEnvironmentArgument(envSpec) && !strings.HasSuffix(envSpec, "-"):
			return nil, nil, fmt.Errorf("%ss must be of the form key=value and can only contain letters, numbers, and underscores", envVarType)
		case envSpec == "-":
			if defaultReader == nil {
				return nil, nil, fmt.Errorf("when '-' is used, STDIN must be open")
			}
			fileEnv, err := readEnv(defaultReader, envVarType)
			if err != nil {
				return nil, nil, err
			}
			env = append(env, fileEnv...)
		case strings.Index(envSpec, "=") != -1:
			parts := strings.SplitN(envSpec, "=", 2)
			if len(parts) != 2 {
				return nil, nil, fmt.Errorf("invalid %s: %v", envVarType, envSpec)
			}
			exists.Insert(parts[0])
			env = append(env, api.EnvVar{
				Name:  parts[0],
				Value: parts[1],
			})
		case strings.HasSuffix(envSpec, "-"):
			remove = append(remove, envSpec[:len(envSpec)-1])
		default:
			return nil, nil, fmt.Errorf("unknown %s: %v", envVarType, envSpec)
		}
	}
	for _, removeLabel := range remove {
		if _, found := exists[removeLabel]; found {
			return nil, nil, fmt.Errorf("can not both modify and remove the same %s in the same command", envVarType)
		}
	}
	return env, remove, nil
}

// ParseEnv parse env from reader
func ParseEnv(spec []string, defaultReader io.Reader) ([]api.EnvVar, []string, error) {
	return parseIntoEnvVar(spec, defaultReader, "environment variable")
}

func readEnv(r io.Reader, envVarType string) ([]api.EnvVar, error) {
	env := []api.EnvVar{}
	scanner := bufio.NewScanner(r)
	for scanner.Scan() {
		envSpec := scanner.Text()
		if pos := strings.Index(envSpec, "#"); pos != -1 {
			envSpec = envSpec[:pos]
		}
		if strings.Index(envSpec, "=") != -1 {
			parts := strings.SplitN(envSpec, "=", 2)
			if len(parts) != 2 {
				return nil, fmt.Errorf("invalid %s: %v", envVarType, envSpec)
			}
			env = append(env, api.EnvVar{
				Name:  parts[0],
				Value: parts[1],
			})
		}
	}
	if err := scanner.Err(); err != nil && err != io.EOF {
		return nil, err
	}
	return env, nil
}