// Copyright (C) The Arvados Authors. All rights reserved.
//
// SPDX-License-Identifier: AGPL-3.0

package config

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"os"

	"git.curoverse.com/arvados.git/sdk/go/arvados"
	"github.com/ghodss/yaml"
	"github.com/imdario/mergo"
)

type logger interface {
	Warnf(string, ...interface{})
}

func LoadFile(path string, log logger) (*arvados.Config, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer f.Close()
	return Load(f, log)
}

func Load(rdr io.Reader, log logger) (*arvados.Config, error) {
	buf, err := ioutil.ReadAll(rdr)
	if err != nil {
		return nil, err
	}

	// Load the config into a dummy map to get the cluster ID
	// keys, discarding the values; then set up defaults for each
	// cluster ID; then load the real config on top of the
	// defaults.
	var dummy struct {
		Clusters map[string]struct{}
	}
	err = yaml.Unmarshal(buf, &dummy)
	if err != nil {
		return nil, err
	}
	if len(dummy.Clusters) == 0 {
		return nil, errors.New("config does not define any clusters")
	}

	// We can't merge deep structs here; instead, we unmarshal the
	// default & loaded config files into generic maps, merge
	// those, and then json-encode+decode the result into the
	// config struct type.
	var merged map[string]interface{}
	for id := range dummy.Clusters {
		var src map[string]interface{}
		err = yaml.Unmarshal(bytes.Replace(DefaultYAML, []byte(" xxxxx:"), []byte(" "+id+":"), -1), &src)
		if err != nil {
			return nil, fmt.Errorf("loading defaults for %s: %s", id, err)
		}
		err = mergo.Merge(&merged, src, mergo.WithOverride)
		if err != nil {
			return nil, fmt.Errorf("merging defaults for %s: %s", id, err)
		}
	}
	var src map[string]interface{}
	err = yaml.Unmarshal(buf, &src)
	if err != nil {
		return nil, fmt.Errorf("loading config data: %s", err)
	}
	err = mergo.Merge(&merged, src, mergo.WithOverride)
	if err != nil {
		return nil, fmt.Errorf("merging config data: %s", err)
	}

	// map[string]interface{} => json => arvados.Config
	var cfg arvados.Config
	var errEnc error
	pr, pw := io.Pipe()
	go func() {
		errEnc = json.NewEncoder(pw).Encode(merged)
		pw.Close()
	}()
	err = json.NewDecoder(pr).Decode(&cfg)
	if errEnc != nil {
		err = errEnc
	}
	if err != nil {
		return nil, fmt.Errorf("transcoding config data: %s", err)
	}

	err = applyDeprecatedConfig(&cfg, buf, log)
	if err != nil {
		return nil, err
	}
	return &cfg, nil
}