package gameserver

import (
	"encoding/json"
	"fmt"
	"sort"
	"sync"

	"gac-hkrpg-go/internal/common"
)

// Tutorial IDs come from the installed Client resource tables, not a list
// copied from an older server build. Restart after replacing these resources.
var tutorialResourceCache struct {
	sync.Once
	tutorials []uint32
	guides    []uint32
	err       error
}

func getTutorialResourceIDs() ([]uint32, []uint32, error) {
	tutorialResourceCache.Do(func() {
		var tutorialFile struct {
			Entries []struct {
				ID uint32 `json:"TutorialID"`
			} `json:"tutorial_config"`
		}
		var guideFile struct {
			Entries []struct {
				ID uint32 `json:"GroupID"`
			} `json:"tutorial_guide_config"`
		}
		load := func(name string, dst any) error {
			path := "resources/" + name
			data, err := common.ReadResourceFile(path)
			if err != nil {
				return fmt.Errorf("tutorial resource %s: %w", path, err)
			}
			if err := json.Unmarshal(data, dst); err != nil {
				return fmt.Errorf("tutorial resource %s: %w", path, err)
			}
			return nil
		}
		if err := load("TutorialData.json", &tutorialFile); err != nil {
			tutorialResourceCache.err = err
			return
		}
		if err := load("TutorialGuideGroup.json", &guideFile); err != nil {
			tutorialResourceCache.err = err
			return
		}
		collect := func(ids []uint32) []uint32 {
			sort.Slice(ids, func(i, j int) bool { return ids[i] < ids[j] })
			out := ids[:0]
			for _, id := range ids {
				if id != 0 && (len(out) == 0 || id != out[len(out)-1]) {
					out = append(out, id)
				}
			}
			return out
		}
		for _, entry := range tutorialFile.Entries {
			tutorialResourceCache.tutorials = append(tutorialResourceCache.tutorials, entry.ID)
		}
		for _, entry := range guideFile.Entries {
			tutorialResourceCache.guides = append(tutorialResourceCache.guides, entry.ID)
		}
		tutorialResourceCache.tutorials = collect(tutorialResourceCache.tutorials)
		tutorialResourceCache.guides = collect(tutorialResourceCache.guides)
		if len(tutorialResourceCache.tutorials) == 0 || len(tutorialResourceCache.guides) == 0 {
			tutorialResourceCache.err = fmt.Errorf("tutorial resource tables contain no IDs")
		}
	})
	return tutorialResourceCache.tutorials, tutorialResourceCache.guides, tutorialResourceCache.err
}