// Copyright 2021 Google LLC
//
// 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 kubeconfig

import (
	"errors"
	"fmt"
	"io"

	"sigs.k8s.io/kustomize/kyaml/yaml"
)

type ReadWriteResetCloser interface {
	io.ReadWriteCloser

	// Reset truncates the file and seeks to the beginning of the file.
	Reset() error
}

type Loader interface {
	Load() ([]ReadWriteResetCloser, error)
}

type Kubeconfig struct {
	loader Loader

	f      ReadWriteResetCloser
	config *yaml.RNode
}

func (k *Kubeconfig) WithLoader(l Loader) *Kubeconfig {
	k.loader = l
	return k
}

func (k *Kubeconfig) Close() error {
	if k.f == nil {
		return nil
	}
	return k.f.Close()
}

func (k *Kubeconfig) Parse() error {
	files, err := k.loader.Load()
	if err != nil {
		return fmt.Errorf("failed to load: %w", err)
	}

	// TODO since we don't support multiple kubeconfig files at the moment, there's just 1 file
	f := files[0]

	k.f = f
	var v yaml.Node
	if err := yaml.NewDecoder(f).Decode(&v); err != nil {
		return fmt.Errorf("failed to decode: %w", err)
	}
	k.config = yaml.NewRNode(&v)
	if k.config.YNode().Kind != yaml.MappingNode {
		return errors.New("kubeconfig file is not a map document")
	}
	return nil
}

func (k *Kubeconfig) Bytes() ([]byte, error) {
	str, err := k.config.String()
	if err != nil {
		return nil, err
	}
	return []byte(str), nil
}

func (k *Kubeconfig) Save() error {
	if err := k.f.Reset(); err != nil {
		return fmt.Errorf("failed to reset file: %w", err)
	}
	enc := yaml.NewEncoder(k.f)
	enc.SetIndent(0)
	if err := enc.Encode(k.config.YNode()); err != nil {
		return err
	}
	return enc.Close()
}