package db

import (
	"context"
	"fmt"
	"time"

	"github.com/jackc/pgx/v5"
)

// ItemDependency represents a row in the item_dependencies table.
type ItemDependency struct {
	ID              string
	ParentItemID    string
	ChildUUID       string
	ChildPartNumber *string
	ChildRevision   *int
	Quantity        *float64
	Label           *string
	Relationship    string
	RevisionNumber  int
	CreatedAt       time.Time
}

// ResolvedDependency extends ItemDependency with resolution info from a LEFT JOIN.
type ResolvedDependency struct {
	ItemDependency
	ResolvedPartNumber *string
	ResolvedRevision   *int
	Resolved           bool
}

// ItemDependencyRepository provides item_dependencies database operations.
type ItemDependencyRepository struct {
	db *DB
}

// NewItemDependencyRepository creates a new item dependency repository.
func NewItemDependencyRepository(db *DB) *ItemDependencyRepository {
	return &ItemDependencyRepository{db: db}
}

// ReplaceForRevision atomically replaces all dependencies for an item's revision.
// Deletes existing rows for the parent item and inserts the new set.
func (r *ItemDependencyRepository) ReplaceForRevision(ctx context.Context, parentItemID string, revisionNumber int, deps []*ItemDependency) error {
	return r.db.Tx(ctx, func(tx pgx.Tx) error {
		_, err := tx.Exec(ctx, `DELETE FROM item_dependencies WHERE parent_item_id = $1`, parentItemID)
		if err != nil {
			return fmt.Errorf("deleting old dependencies: %w", err)
		}

		for _, d := range deps {
			_, err := tx.Exec(ctx, `
				INSERT INTO item_dependencies
					(parent_item_id, child_uuid, child_part_number, child_revision,
					 quantity, label, relationship, revision_number)
				VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
			`, parentItemID, d.ChildUUID, d.ChildPartNumber, d.ChildRevision,
				d.Quantity, d.Label, d.Relationship, revisionNumber)
			if err != nil {
				return fmt.Errorf("inserting dependency: %w", err)
			}
		}
		return nil
	})
}

// ListByItem returns all dependencies for an item.
func (r *ItemDependencyRepository) ListByItem(ctx context.Context, parentItemID string) ([]*ItemDependency, error) {
	rows, err := r.db.pool.Query(ctx, `
		SELECT id, parent_item_id, child_uuid, child_part_number, child_revision,
		       quantity, label, relationship, revision_number, created_at
		FROM item_dependencies
		WHERE parent_item_id = $1
		ORDER BY label NULLS LAST
	`, parentItemID)
	if err != nil {
		return nil, fmt.Errorf("listing dependencies: %w", err)
	}
	defer rows.Close()

	var deps []*ItemDependency
	for rows.Next() {
		d := &ItemDependency{}
		if err := rows.Scan(
			&d.ID, &d.ParentItemID, &d.ChildUUID, &d.ChildPartNumber, &d.ChildRevision,
			&d.Quantity, &d.Label, &d.Relationship, &d.RevisionNumber, &d.CreatedAt,
		); err != nil {
			return nil, fmt.Errorf("scanning dependency: %w", err)
		}
		deps = append(deps, d)
	}
	return deps, nil
}

// Resolve returns dependencies with child UUIDs resolved against the items table.
// Unresolvable UUIDs (external or deleted items) have Resolved=false.
func (r *ItemDependencyRepository) Resolve(ctx context.Context, parentItemID string) ([]*ResolvedDependency, error) {
	rows, err := r.db.pool.Query(ctx, `
		SELECT d.id, d.parent_item_id, d.child_uuid, d.child_part_number, d.child_revision,
		       d.quantity, d.label, d.relationship, d.revision_number, d.created_at,
		       i.part_number, i.current_revision
		FROM item_dependencies d
		LEFT JOIN items i ON i.id = d.child_uuid AND i.archived_at IS NULL
		WHERE d.parent_item_id = $1
		ORDER BY d.label NULLS LAST
	`, parentItemID)
	if err != nil {
		return nil, fmt.Errorf("resolving dependencies: %w", err)
	}
	defer rows.Close()

	var deps []*ResolvedDependency
	for rows.Next() {
		d := &ResolvedDependency{}
		if err := rows.Scan(
			&d.ID, &d.ParentItemID, &d.ChildUUID, &d.ChildPartNumber, &d.ChildRevision,
			&d.Quantity, &d.Label, &d.Relationship, &d.RevisionNumber, &d.CreatedAt,
			&d.ResolvedPartNumber, &d.ResolvedRevision,
		); err != nil {
			return nil, fmt.Errorf("scanning resolved dependency: %w", err)
		}
		d.Resolved = d.ResolvedPartNumber != nil
		deps = append(deps, d)
	}
	return deps, nil
}