package util

import (
	"bytes"
	"encoding/json"
	"errors"
	"log"
	"os"
	"path"
	"slices"

	"gitlab.hamburg.ccc.de/ccchh/spaceapid/types"
)

const savedStateJSONPath = "/var/lib/spaceapid/spaceapid-state.json"

// ParseTemplate parses the given file and
func ParseTemplate(file string) (resp types.SpaceAPIResponseV14) {

	// Read template file
	template, err := os.ReadFile(file)
	if err != nil {
		log.Fatalln("Failed reading file:", err)
	}

	// Parse JSON
	dec := json.NewDecoder(bytes.NewReader(template))
	dec.DisallowUnknownFields()
	err = dec.Decode(&resp)
	if err != nil {
		log.Fatalln("Could not parse SpaceAPI response template:", err)
	}

	// Check if compatible with v14
	if !slices.Contains(resp.APICompatibility, "14") {
		log.Fatalln("Provided template doesn't specify compatibility with API version 14")
	}

	return
}

// MergeOldState merges a given SpaceAPIResponse with the state saved at the time of last program exit and then deletes
// the file containing the old state.
func MergeOldState(response *types.SpaceAPIResponseV14) {
	var (
		err      error
		oldState []byte
	)

	// Check if state.json is present
	_, err = os.Stat(savedStateJSONPath)
	if err != nil {
		log.Println("Old state json not accessible at", savedStateJSONPath, ", skipping merge... error:", err)
		if errors.Is(err, os.ErrNotExist) {
			return
		}
		goto removeOld
	}

	// Read file and merge
	oldState, err = os.ReadFile(savedStateJSONPath)
	if err != nil {
		log.Println("Error reading old state from", savedStateJSONPath, ", skipping merge... error:", err)
		goto removeOld
	}
	err = json.Unmarshal(oldState, response)
	if err != nil {
		log.Println(savedStateJSONPath, "doesn't seem to contain valid data... error:", err)
		goto removeOld
	}

	// Delete old state json
removeOld:
	err = os.RemoveAll(savedStateJSONPath)
	if err != nil {
		log.Println("Failed to remove", savedStateJSONPath, ", continuing... error:", err)
	}
}

func SaveCurrentState(response types.SpaceAPIResponseV14) {
	// Create state directory if not present
	err := os.MkdirAll(path.Dir(savedStateJSONPath), 0750)
	if err != nil {
		log.Fatalln("Failed creating", savedStateJSONPath, ", aborting... error:", err)
	}

	// Open persistent state file for reading
	file, err := os.OpenFile(savedStateJSONPath, os.O_RDWR|os.O_CREATE, 0644)
	if err != nil {
		log.Fatalln("Failed opening", savedStateJSONPath, "while trying to save current state... error:", err)
	}
	defer func(file *os.File) {
		_ = file.Close()
	}(file)

	// Create persistent state
	persistentStateV14 := types.PersistentStateV14{
		State: struct {
			Open       bool  `json:"open"`
			LastChange int64 `json:"lastchange"`
		}{Open: response.State.Open, LastChange: response.State.LastChange},
	}

	// Serialize persistent state
	marshal, err := json.MarshalIndent(persistentStateV14, "", "\t")
	if err != nil {
		log.Fatalln("Failed serializing persistent state... error:", err)
	}

	// Write to file
	_, err = file.Write(marshal)
	if err != nil {
		log.Fatalln("Failed writing persistent state to file", file.Name(), "... error:", err)
	}
}