package core

import (
	"context"
	"time"

	"github.com/google/uuid"
	"lukechampine.com/blake3"
)

type Ledger struct {
	LedgerID LedgerID

	entryStore   EntryStore
	payloadStore PayloadStore

	hashChaining bool
}

func NewLedger(entryStore EntryStore, payloadStore PayloadStore) (*Ledger, error) {
	id, err := uuid.NewV7()
	if err != nil {
		return nil, err
	}

	idByes, err := id.MarshalBinary()
	if err != nil {
		return nil, err
	}

	return &Ledger{
		LedgerID:     LedgerID(idByes),
		entryStore:   entryStore,
		payloadStore: payloadStore,
	}, nil
}

func (l *Ledger) ID() LedgerID {
	return l.LedgerID
}

func (l *Ledger) Head() (Entry, error) {
	panic("unimplemented")
}

func (l *Ledger) Append(ctx context.Context, payload []byte) (EntryID, error) {
	payloadDigest := blake3.Sum256(payload)
	payloadID, err := l.payloadStore.Put(ctx, payload)
	if err != nil {
		return EntryID{}, err
	}

	entryID, err := uuid.NewV7()
	entryIDBytes, err := entryID.MarshalBinary()
	if err != nil {
		return EntryID{}, err
	}

	head, err := l.Head()
	if err != nil {
		return EntryID{}, err
	}

	entry := Entry{
		EntryID:       EntryID(entryIDBytes),
		LedgerID:      l.LedgerID,
		Seq:           head.Seq + 1,
		Timestamp:     time.Now(),
		PayloadID:     payloadID,
		PayloadDigest: payloadDigest,
	}

	entryHash := HashEntry(entry)
	entry.EntryHash = entryHash

	err = l.entryStore.Append(ctx, entry)
	if err != nil {
		return EntryID{}, err
	}

	return EntryID(entryIDBytes), nil
}

func (l *Ledger) Get(ctx context.Context, seq uint64) (Entry, []byte, error) {
	entry, err := l.entryStore.GetBySeq(ctx, l.LedgerID, seq)
	if err != nil {
		return Entry{}, nil, err
	}
	payload, err := l.payloadStore.Get(ctx, entry.PayloadID)
	if err != nil {
		return Entry{}, nil, err
	}

	return entry, payload, nil
}

func (l *Ledger) GetEntry(ctx context.Context, seq uint64) (Entry, error) {
	panic("unimplemented")
}

func (l *Ledger) GetPayload(ctx context.Context, seq uint64) ([]byte, error) {
	panic("unimplemented")
}

func (l *Ledger) Iter(ctx context.Context, startSeq uint64) (EntryIterator, error) {
	panic("unimplemented")
}