package store

import (
	"context"
	"errors"
)

// ErrLastAdmin is returned when demoting the only remaining admin.
var ErrLastAdmin = errors.New("cannot demote the last admin")

// Role is a user privilege level stored in users.role.
type Role string

const (
	RoleUser  Role = "user"
	RoleAdmin Role = "admin"
)

// NewUser is the input for CreateUser.
type NewUser struct {
	Username     string
	PasswordHash string
	Role         Role
}

// DB is the persistence API used by the web layer.
// Named DB to avoid colliding with scs.Store.
type DB interface {
	CreateUser(ctx context.Context, user NewUser) (*User, error)
	UserByID(ctx context.Context, id string) (*User, error)
	UserByUsername(ctx context.Context, username string) (*User, error)
	CountAdmins(ctx context.Context) (int, error)
	ListUsers(ctx context.Context) ([]User, error)
	SetRole(ctx context.Context, userID string, role Role) error
	CreateQuestion(ctx context.Context, authorID, title, body, city string) (*RankedQuestion, error)
	ListHunt(ctx context.Context, huntDate, viewerID string) ([]RankedQuestion, error)
	GetQuestion(ctx context.Context, id, viewerID string) (*RankedQuestion, error)
	Vote(ctx context.Context, userID, questionID string, value int) error
	GetAnswer(ctx context.Context, questionID string) (*Answer, error)
	UpsertAnswer(ctx context.Context, questionID, authorID, body string) error
	HideQuestion(ctx context.Context, id string) error
	UpdateProfile(ctx context.Context, userID, state, avatarURL string) error
	ListQuestionsByAuthor(ctx context.Context, authorID string) ([]RankedQuestion, error)
	ListQuestionsAnsweredBy(ctx context.Context, adminID string) ([]RankedQuestion, error)
}

// Compile-time check: *Store implements DB.
var _ DB = (*Store)(nil)