// Package models defines the data models used by the chat application.
// All model structs embed Base, which provides database access for
// relation-fetching methods directly on model instances.
package models

import (
	"context"
	"database/sql"
	"errors"
)

// DB is the interface that models use to query the database.
// This avoids a circular import with the db package.
type DB interface {
	GetDB() *sql.DB
}

// UserLookup provides user lookup by ID without circular imports.
type UserLookup interface {
	GetUserByID(ctx context.Context, id string) (*User, error)
}

// ChannelLookup provides channel lookup by ID without circular imports.
type ChannelLookup interface {
	GetChannelByID(ctx context.Context, id string) (*Channel, error)
}

// Sentinel errors for model lookup methods.
var (
	ErrUserLookupNotAvailable    = errors.New("user lookup not available")
	ErrChannelLookupNotAvailable = errors.New("channel lookup not available")
)

// Base is embedded in all model structs to provide database access.
type Base struct {
	db DB
}

// SetDB injects the database reference into a model.
func (b *Base) SetDB(d DB) {
	b.db = d
}

// GetDB returns the database interface for use in model methods.
func (b *Base) GetDB() *sql.DB {
	return b.db.GetDB()
}

// GetUserLookup returns the DB as a UserLookup if it implements the interface.
func (b *Base) GetUserLookup() UserLookup { //nolint:ireturn // interface return is intentional
	if ul, ok := b.db.(UserLookup); ok {
		return ul
	}

	return nil
}

// GetChannelLookup returns the DB as a ChannelLookup if it implements the interface.
func (b *Base) GetChannelLookup() ChannelLookup { //nolint:ireturn // interface return is intentional
	if cl, ok := b.db.(ChannelLookup); ok {
		return cl
	}

	return nil
}