// Package env is adapted from go-kratos/kratos config/env.
//
// Upstream: https://github.com/go-kratos/kratos/tree/v2.9.2/config/env
// License: MIT, see ../LICENSE.kratos.
package env

import (
	"os"
	"strings"

	"github.com/geo-platform/tenant-api/internal/shared/config/runtime"
)

type env struct {
	prefixes []string
}

func NewSource(prefixes ...string) runtime.Source {
	return &env{prefixes: prefixes}
}

func (e *env) Load() ([]*runtime.KeyValue, error) {
	return e.load(os.Environ()), nil
}

func (e *env) load(envs []string) []*runtime.KeyValue {
	kvs := make([]*runtime.KeyValue, 0, len(envs))
	for _, item := range envs {
		key, value, _ := strings.Cut(item, "=")
		if key == "" {
			continue
		}
		if len(e.prefixes) > 0 {
			prefix, ok := matchPrefix(e.prefixes, key)
			if !ok || key == prefix {
				continue
			}
			key = strings.TrimPrefix(key, prefix)
			key = strings.TrimPrefix(key, "_")
		}
		if key != "" {
			kvs = append(kvs, &runtime.KeyValue{
				Key:   key,
				Value: []byte(value),
			})
		}
	}
	return kvs
}

func (e *env) Watch() (runtime.Watcher, error) {
	return NewWatcher()
}

func matchPrefix(prefixes []string, s string) (string, bool) {
	for _, p := range prefixes {
		if strings.HasPrefix(s, p) {
			return p, true
		}
	}
	return "", false
}