package main

import (
	"context"
	"encoding/hex"
	"errors"
	"fmt"
	"sort"

	"git.michelsen.id/chron/core"
)

type InProcEntryStore struct {
	entries map[core.EntryID]core.Entry
}

func (e *InProcEntryStore) Store(ctx context.Context, entry core.Entry) error {
	if _, ok := e.entries[entry.EntryID]; ok {
		return errors.New("entry already exists")
	}
	e.entries[entry.EntryID] = entry
	return nil
}

func (e *InProcEntryStore) Load(ctx context.Context, id core.EntryID) (core.Entry, error) {
	entry, ok := e.entries[id]
	if !ok {
		return core.Entry{}, errors.New("entry does not exist")
	}
	return entry, nil
}

func (e *InProcEntryStore) Exists(ctx context.Context, id core.EntryID) (bool, error) {
	_, ok := e.entries[id]
	return ok, nil
}

func (e *InProcEntryStore) Delete(ctx context.Context, id core.EntryID) error {
	if _, ok := e.entries[id]; !ok {
		return errors.New("entry does not exist")
	}
	delete(e.entries, id)
	return nil
}

type InProcReferenceStore struct {
	references map[string]core.EntryID
}

func (r *InProcReferenceStore) Set(ctx context.Context, name string, entryID core.EntryID) error {
	r.references[name] = entryID
	return nil
}

func (r *InProcReferenceStore) Get(ctx context.Context, name string) (core.EntryID, bool, error) {
	entryID, ok := r.references[name]
	if !ok {
		return core.EntryID{}, false, nil
	}
	return entryID, true, nil
}

func (r *InProcReferenceStore) Delete(ctx context.Context, name string) error {
	if _, ok := r.references[name]; !ok {
		return errors.New("reference does not exist")
	}
	delete(r.references, name)
	return nil
}

func main() {
	ctx := context.TODO()

	entryStore := InProcEntryStore{
		entries: make(map[core.EntryID]core.Entry),
	}
	referenceStore := InProcReferenceStore{
		references: make(map[string]core.EntryID),
	}

	ledger, err := core.NewLedger(&entryStore, &referenceStore)
	if err != nil {
		fmt.Println(err)
		return
	}

	for i := range 1000000 {
		data := fmt.Sprintf("test%d", i)

		err = ledger.Append(ctx, []byte(data))
		if err != nil {
			fmt.Println(err)
			return
		}
	}

	entries := make([]core.Entry, 0, len(entryStore.entries))
	for _, e := range entryStore.entries {
		entries = append(entries, e)
	}

	sort.Slice(entries, func(i, j int) bool {
		if entries[i].Timestamp.Equal(entries[j].Timestamp) {
			return hex.EncodeToString(entries[i].EntryID[:]) <
				hex.EncodeToString(entries[j].EntryID[:])
		}
		return entries[i].Timestamp.Before(entries[j].Timestamp)
	})

	headID, ok, err := referenceStore.Get(ctx, "HEAD")
	if err != nil {
		fmt.Println("get HEAD:", err)
		return
	}
	if !ok {
		fmt.Println("HEAD reference not set")
		return
	}

	isZero32 := func(b [32]byte) bool {
		for _, v := range b {
			if v != 0 {
				return false
			}
		}
		return true
	}

	curID := headID
	for {
		ent, err := entryStore.Load(ctx, curID)
		if err != nil {
			return
		}

		if isZero32(ent.Parents) {
			break
		}

		// Follow the linked list backwards
		curID = core.EntryID(ent.Parents)
	}
}