// Package items is the reference vertical slice: model, repository
// interface, Bun implementation, and service. To add a new resource, copy
// this package's shape and register its routes in internal/api.
package items

import (
	"context"
	"errors"
	"time"

	"github.com/uptrace/bun"
)

// Status is the lifecycle state of an item, stored as text.
type Status string

const (
	StatusActive   Status = "active"
	StatusArchived Status = "archived"
)

// Valid reports whether s is a known status value.
func (s Status) Valid() bool {
	return s == StatusActive || s == StatusArchived
}

// Item is the persisted model. Struct tags are Bun's mapping; json tags
// define the wire format (camelCase, matching the frontend).
type Item struct {
	bun.BaseModel `bun:"table:items,alias:i"`

	ID          int64     `bun:"id,pk,autoincrement"            json:"id"`
	Title       string    `bun:"title,notnull"                  json:"title"`
	Description string    `bun:"description,nullzero"           json:"description"`
	Status      Status    `bun:"status,notnull,default:'active'" json:"status"`
	CreatedAt   time.Time `bun:"created_at,notnull,default:current_timestamp" json:"createdAt"`
	UpdatedAt   time.Time `bun:"updated_at,notnull,default:current_timestamp" json:"updatedAt"`
}

// BeforeAppendModel stamps timestamps on INSERT and UPDATE queries.
// Postgres stores microsecond UTC; truncate + UTC so values set in Go
// (PATCH responses) match what round-trips through the database.
func (i *Item) BeforeAppendModel(_ context.Context, query bun.Query) error {
	now := time.Now().UTC().Truncate(time.Microsecond)
	switch query.(type) {
	case *bun.InsertQuery:
		i.CreatedAt, i.UpdatedAt = now, now
	case *bun.UpdateQuery:
		i.UpdatedAt = now
	}
	return nil
}

// Filter narrows and pages List queries. Apply normalizeFilter (via the
// service) before handing one to a repository.
type Filter struct {
	Status Status
	Limit  int
	Offset int
}

// List result paging defaults, applied by normalizeFilter.
const (
	DefaultLimit = 50
	MaxLimit     = 100
)

// Repository is the persistence contract for items. The service depends on
// this interface — not on Bun — so tests use in-memory fakes and other
// backends remain possible.
type Repository interface {
	List(ctx context.Context, f Filter) ([]Item, error)
	Get(ctx context.Context, id int64) (Item, error)
	Create(ctx context.Context, item *Item) error
	Update(ctx context.Context, item *Item) error
	Delete(ctx context.Context, id int64) error
}

// ErrNotFound is returned by repositories and services when an item does
// not exist. Handlers map it to 404.
var ErrNotFound = errors.New("item not found")

// ValidationError reports an invalid field value. Handlers map it to 400.
type ValidationError struct {
	Field  string
	Reason string
}

func (e *ValidationError) Error() string { return e.Field + ": " + e.Reason }