package secret

import (
	"bufio"
	"io"
	"os"
	"strings"
	"syscall"
)

type environment map[string][]byte

// Environment provides environment variables as secrets.
func Environment() Provider {
	return EnvironmentPrefix("")
}

// EnvironmentPrefix provides environment variables with a prefix as secrets.
//
// The prefix is stripped from the final secret key name.
func EnvironmentPrefix(prefix string) Provider {
	env := make(environment)
	for _, line := range syscall.Environ() {
		if !strings.HasPrefix(line, prefix) {
			continue
		}
		kv := strings.SplitN(line[len(prefix):], "=", 2)
		if len(kv) == 2 {
			env[kv[0]] = []byte(strings.TrimSpace(kv[1]))
		}
	}
	return env
}

// EnvironmentFile reads a file containing key-value pairs.
//
// Line starting with `#` or `//` are ignored.
//
// Example:
//
//	key=value
//	# This comment is ignored
func EnvironmentFile(name string) (Provider, error) {
	f, err := os.Open(name)
	if err != nil {
		return nil, err
	}
	defer func() { _ = f.Close() }()
	return EnvironmentReader(f)
}

// EnvironmentReader reads key-value pairs separated by newlines.
//
// Line starting with `#` or `//` are ignored.
//
// Example:
//
//	key=value
//	# This comment is ignored
func EnvironmentReader(r io.Reader) (Provider, error) {
	s := bufio.NewScanner(r)
	s.Split(bufio.ScanLines)

	env := make(environment)
	for s.Scan() {
		if err := s.Err(); err != nil {
			if err == io.EOF {
				break
			}
			return nil, err
		}

		line := strings.TrimSpace(s.Text())
		if strings.HasPrefix(line, "#") || strings.HasPrefix(line, "//") {
			continue
		}

		kv := strings.SplitN(line, "=", 2)
		if len(kv) == 2 {
			env[strings.TrimSpace(kv[0])] = []byte(strings.TrimSpace(kv[1]))
		}
	}

	return env, nil
}

func (env environment) GetSecret(key string) (value []byte, err error) {
	var ok bool
	if value, ok = env[key]; ok {
		return
	}
	return nil, NotFound{key}
}