package memory

import (
	"context"
	"crypto/rand"
	"sync"

	"github.com/snip/backend/internal/domain"
)

type UserRepo struct {
	mu     sync.RWMutex
	byID   map[string]*domain.User
	byKey  map[string]string // provider|subject -> id
}

func NewUserRepo() *UserRepo {
	return &UserRepo{byID: make(map[string]*domain.User), byKey: make(map[string]string)}
}

func (r *UserRepo) Upsert(_ context.Context, u *domain.User) (*domain.User, error) {
	r.mu.Lock()
	defer r.mu.Unlock()
	key := u.Provider + "|" + u.Subject
	if id, ok := r.byKey[key]; ok {
		existing := r.byID[id]
		existing.Email = u.Email
		existing.Name = u.Name
		cp := *existing
		return &cp, nil
	}
	id := randomID()
	u.ID = id
	r.byID[id] = u
	r.byKey[key] = id
	cp := *u
	return &cp, nil
}

func (r *UserRepo) GetByID(_ context.Context, id string) (*domain.User, error) {
	r.mu.RLock()
	defer r.mu.RUnlock()
	u, ok := r.byID[id]
	if !ok {
		return nil, domain.ErrNotFound
	}
	cp := *u
	return &cp, nil
}

func randomID() string {
	const hex = "0123456789abcdef"
	b := make([]byte, 16)
	_, _ = rand.Read(b)
	out := make([]byte, 16)
	for i := range out {
		out[i] = hex[int(b[i])%16]
	}
	return "u_" + string(out)
}