package osbuild

import (

	"encoding/json"

	"fmt"

)

// A Stage transforms a filesystem tree.

type Stage struct {

	// Well-known name in reverse domain-name notation, uniquely identifying

	// the stage type.

	Name string `json:"name"`

	// Stage-type specific options fully determining the operations of the

	// stage.

	Options StageOptions `json:"options"`

}

// StageOptions specify the operations of a given stage-type.

type StageOptions interface {

	isStageOptions()

}

type rawStage struct {

	Name    string          `json:"name"`

	Options json.RawMessage `json:"options"`

}

// UnmarshalJSON unmarshals JSON into a Stage object. Each type of stage has

// a custom unmarshaller for its options, selected based on the stage name.

func (stage *Stage) UnmarshalJSON(data []byte) error {

	var rawStage rawStage

	err := json.Unmarshal(data, &rawStage)

	if err != nil {

		return err

	}

	var options StageOptions

	switch rawStage.Name {

	case "org.osbuild.fix-bls":

		// TODO: verify that we can unmarshall this also if "options" is omitted

		options = new(FixBLSStageOptions)

	case "org.osbuild.fstab":

		options = new(FSTabStageOptions)

	case "org.osbuild.grub2":

		options = new(GRUB2StageOptions)

	case "org.osbuild.locale":

		options = new(LocaleStageOptions)

	case "org.osbuild.selinux":

		options = new(SELinuxStageOptions)

	case "org.osbuild.hostname":

		options = new(HostnameStageOptions)

	case "org.osbuild.users":

		options = new(UsersStageOptions)

	case "org.osbuild.groups":

		options = new(GroupsStageOptions)

	case "org.osbuild.timezone":

		options = new(TimezoneStageOptions)

	case "org.osbuild.chrony":

		options = new(ChronyStageOptions)

	case "org.osbuild.keymap":

		options = new(KeymapStageOptions)

	case "org.osbuild.firewall":

		options = new(FirewallStageOptions)

	case "org.osbuild.rhsm":

		options = new(RHSMStageOptions)

	case "org.osbuild.rpm":

		options = new(RPMStageOptions)

	case "org.osbuild.rpm-ostree":

		options = new(RPMOSTreeStageOptions)

	case "org.osbuild.systemd":

		options = new(SystemdStageOptions)

	case "org.osbuild.script":

		options = new(ScriptStageOptions)

	default:

		return fmt.Errorf("unexpected stage name: %s", rawStage.Name)

	}

	err = json.Unmarshal(rawStage.Options, options)

	if err != nil {

		return err

	}

	stage.Name = rawStage.Name

	stage.Options = options

	return nil

}