package db

import (
	"context"
	"encoding/json"
	"fmt"
	"time"

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

// Item represents an item in the database.
type Item struct {
	ID              string
	PartNumber      string
	SchemaID        *string
	ItemType        string
	Description     string
	CreatedAt       time.Time
	UpdatedAt       time.Time
	ArchivedAt      *time.Time
	CurrentRevision int
	CADSyncedAt     *time.Time
	CADFilePath     *string
	CreatedBy       *string
	UpdatedBy       *string
	SourcingType    string  // "manufactured" or "purchased"
	LongDescription *string // extended description
	ThumbnailKey    *string // MinIO key for item thumbnail
}

// Revision represents a revision record.
type Revision struct {
	ID             string
	ItemID         string
	RevisionNumber int
	Properties     map[string]any
	FileKey            *string
	FileVersion        *string
	FileChecksum       *string
	FileSize           *int64
	FileStorageBackend string // "minio" or "filesystem"
	ThumbnailKey       *string
	CreatedAt      time.Time
	CreatedBy      *string
	Comment        *string
	Status         string   // draft, review, released, obsolete
	Labels         []string // arbitrary tags
}

// RevisionStatus constants
const (
	RevisionStatusDraft    = "draft"
	RevisionStatusReview   = "review"
	RevisionStatusReleased = "released"
	RevisionStatusObsolete = "obsolete"
)

// PropertyChange represents a change in a property value between revisions.
type PropertyChange struct {
	OldValue any `json:"old_value"`
	NewValue any `json:"new_value"`
}

// RevisionDiff represents the differences between two revisions.
type RevisionDiff struct {
	FromRevision int                       `json:"from_revision"`
	ToRevision   int                       `json:"to_revision"`
	FromStatus   string                    `json:"from_status"`
	ToStatus     string                    `json:"to_status"`
	FileChanged  bool                      `json:"file_changed"`
	FileSizeDiff *int64                    `json:"file_size_diff,omitempty"`
	Added        map[string]any            `json:"added,omitempty"`
	Removed      map[string]any            `json:"removed,omitempty"`
	Changed      map[string]PropertyChange `json:"changed,omitempty"`
}

// ItemRepository provides item database operations.
type ItemRepository struct {
	db *DB
}

// NewItemRepository creates a new item repository.
func NewItemRepository(db *DB) *ItemRepository {
	return &ItemRepository{db: db}
}

// Create inserts a new item and its initial revision.
func (r *ItemRepository) Create(ctx context.Context, item *Item, properties map[string]any) error {
	return r.db.Tx(ctx, func(tx pgx.Tx) error {
		// Insert item
		sourcingType := item.SourcingType
		if sourcingType == "" {
			sourcingType = "manufactured"
		}
		err := tx.QueryRow(ctx, `
			INSERT INTO items (part_number, schema_id, item_type, description, created_by,
			                   sourcing_type, long_description)
			VALUES ($1, $2, $3, $4, $5, $6, $7)
			RETURNING id, created_at, updated_at, current_revision
		`, item.PartNumber, item.SchemaID, item.ItemType, item.Description, item.CreatedBy,
			sourcingType, item.LongDescription,
		).Scan(
			&item.ID, &item.CreatedAt, &item.UpdatedAt, &item.CurrentRevision,
		)
		if err != nil {
			return fmt.Errorf("inserting item: %w", err)
		}

		// Insert initial revision
		propsJSON, err := json.Marshal(properties)
		if err != nil {
			return fmt.Errorf("marshaling properties: %w", err)
		}

		_, err = tx.Exec(ctx, `
			INSERT INTO revisions (item_id, revision_number, properties, created_by)
			VALUES ($1, 1, $2, $3)
		`, item.ID, propsJSON, item.CreatedBy)
		if err != nil {
			return fmt.Errorf("inserting revision: %w", err)
		}

		return nil
	})
}

// GetByPartNumber retrieves an item by part number.
func (r *ItemRepository) GetByPartNumber(ctx context.Context, partNumber string) (*Item, error) {
	item := &Item{}
	err := r.db.pool.QueryRow(ctx, `
		SELECT id, part_number, schema_id, item_type, description,
		       created_at, updated_at, archived_at, current_revision,
		       cad_synced_at, cad_file_path,
		       sourcing_type, long_description,
		       thumbnail_key
		FROM items
		WHERE part_number = $1 AND archived_at IS NULL
	`, partNumber).Scan(
		&item.ID, &item.PartNumber, &item.SchemaID, &item.ItemType, &item.Description,
		&item.CreatedAt, &item.UpdatedAt, &item.ArchivedAt, &item.CurrentRevision,
		&item.CADSyncedAt, &item.CADFilePath,
		&item.SourcingType, &item.LongDescription,
		&item.ThumbnailKey,
	)
	if err == pgx.ErrNoRows {
		return nil, nil
	}
	if err != nil {
		return nil, fmt.Errorf("querying item: %w", err)
	}
	return item, nil
}

// GetByID retrieves an item by ID.
func (r *ItemRepository) GetByID(ctx context.Context, id string) (*Item, error) {
	item := &Item{}
	err := r.db.pool.QueryRow(ctx, `
		SELECT id, part_number, schema_id, item_type, description,
		       created_at, updated_at, archived_at, current_revision,
		       cad_synced_at, cad_file_path,
		       sourcing_type, long_description,
		       thumbnail_key
		FROM items
		WHERE id = $1
	`, id).Scan(
		&item.ID, &item.PartNumber, &item.SchemaID, &item.ItemType, &item.Description,
		&item.CreatedAt, &item.UpdatedAt, &item.ArchivedAt, &item.CurrentRevision,
		&item.CADSyncedAt, &item.CADFilePath,
		&item.SourcingType, &item.LongDescription,
		&item.ThumbnailKey,
	)
	if err == pgx.ErrNoRows {
		return nil, nil
	}
	if err != nil {
		return nil, fmt.Errorf("querying item: %w", err)
	}
	return item, nil
}

// List retrieves items with optional filtering.
func (r *ItemRepository) List(ctx context.Context, opts ListOptions) ([]*Item, error) {
	// Build query - use JOIN if filtering by project
	var query string
	args := []any{}
	argNum := 1

	if opts.Project != "" {
		// Filter by project via many-to-many relationship
		query = `
			SELECT DISTINCT i.id, i.part_number, i.schema_id, i.item_type, i.description,
			       i.created_at, i.updated_at, i.archived_at, i.current_revision,
			       i.sourcing_type, i.long_description,
			       i.thumbnail_key
			FROM items i
			JOIN item_projects ip ON ip.item_id = i.id
			JOIN projects p ON p.id = ip.project_id
			WHERE i.archived_at IS NULL AND p.code = $1
		`
		args = append(args, opts.Project)
		argNum++
	} else {
		query = `
			SELECT id, part_number, schema_id, item_type, description,
			       created_at, updated_at, archived_at, current_revision,
			       sourcing_type, long_description,
			       thumbnail_key
			FROM items
			WHERE archived_at IS NULL
		`
	}

	if opts.ItemType != "" {
		query += fmt.Sprintf(" AND item_type = $%d", argNum)
		args = append(args, opts.ItemType)
		argNum++
	}

	if opts.Search != "" {
		if opts.Project != "" {
			query += fmt.Sprintf(" AND (i.part_number ILIKE $%d OR i.description ILIKE $%d)", argNum, argNum)
		} else {
			query += fmt.Sprintf(" AND (part_number ILIKE $%d OR description ILIKE $%d)", argNum, argNum)
		}
		args = append(args, "%"+opts.Search+"%")
		argNum++
	}

	if opts.Project != "" {
		query += " ORDER BY i.part_number"
	} else {
		query += " ORDER BY part_number"
	}

	if opts.Limit > 0 {
		query += fmt.Sprintf(" LIMIT $%d", argNum)
		args = append(args, opts.Limit)
		argNum++
	}

	if opts.Offset > 0 {
		query += fmt.Sprintf(" OFFSET $%d", argNum)
		args = append(args, opts.Offset)
	}

	rows, err := r.db.pool.Query(ctx, query, args...)
	if err != nil {
		return nil, fmt.Errorf("querying items: %w", err)
	}
	defer rows.Close()

	var items []*Item
	for rows.Next() {
		item := &Item{}
		err := rows.Scan(
			&item.ID, &item.PartNumber, &item.SchemaID, &item.ItemType, &item.Description,
			&item.CreatedAt, &item.UpdatedAt, &item.ArchivedAt, &item.CurrentRevision,
			&item.SourcingType, &item.LongDescription,
			&item.ThumbnailKey,
		)
		if err != nil {
			return nil, fmt.Errorf("scanning item: %w", err)
		}
		items = append(items, item)
	}

	return items, nil
}

// ListProjects returns all project codes from the projects table.
// Deprecated: Use ProjectRepository.List() instead for full project details.
func (r *ItemRepository) ListProjects(ctx context.Context) ([]string, error) {
	rows, err := r.db.pool.Query(ctx, `
		SELECT code FROM projects ORDER BY code
	`)
	if err != nil {
		return nil, fmt.Errorf("querying projects: %w", err)
	}
	defer rows.Close()

	var projects []string
	for rows.Next() {
		var code string
		if err := rows.Scan(&code); err != nil {
			return nil, fmt.Errorf("scanning project: %w", err)
		}
		projects = append(projects, code)
	}

	return projects, nil
}

// ListOptions configures item listing.
type ListOptions struct {
	ItemType string
	Search   string
	Project  string
	Limit    int
	Offset   int
}

// CreateRevision adds a new revision for an item.
func (r *ItemRepository) CreateRevision(ctx context.Context, rev *Revision) error {
	propsJSON, err := json.Marshal(rev.Properties)
	if err != nil {
		return fmt.Errorf("marshaling properties: %w", err)
	}

	if rev.FileStorageBackend == "" {
		rev.FileStorageBackend = "minio"
	}

	err = r.db.pool.QueryRow(ctx, `
		INSERT INTO revisions (
			item_id, revision_number, properties, file_key, file_version,
			file_checksum, file_size, file_storage_backend, thumbnail_key, created_by, comment
		)
		SELECT $1, current_revision + 1, $2, $3, $4, $5, $6, $7, $8, $9, $10
		FROM items WHERE id = $1
		RETURNING id, revision_number, created_at
	`, rev.ItemID, propsJSON, rev.FileKey, rev.FileVersion,
		rev.FileChecksum, rev.FileSize, rev.FileStorageBackend, rev.ThumbnailKey, rev.CreatedBy, rev.Comment,
	).Scan(&rev.ID, &rev.RevisionNumber, &rev.CreatedAt)
	if err != nil {
		return fmt.Errorf("inserting revision: %w", err)
	}

	return nil
}

// GetRevisions retrieves all revisions for an item.
func (r *ItemRepository) GetRevisions(ctx context.Context, itemID string) ([]*Revision, error) {
	// Check if status column exists (migration 007 applied)
	var hasStatusColumn bool
	err := r.db.pool.QueryRow(ctx, `
		SELECT EXISTS (
			SELECT 1 FROM information_schema.columns
			WHERE table_name = 'revisions' AND column_name = 'status'
		)
	`).Scan(&hasStatusColumn)
	if err != nil {
		return nil, fmt.Errorf("checking schema: %w", err)
	}

	var rows pgx.Rows
	if hasStatusColumn {
		rows, err = r.db.pool.Query(ctx, `
			SELECT id, item_id, revision_number, properties, file_key, file_version,
			       file_checksum, file_size, COALESCE(file_storage_backend, 'minio'),
			       thumbnail_key, created_at, created_by, comment,
			       COALESCE(status, 'draft') as status, COALESCE(labels, ARRAY[]::TEXT[]) as labels
			FROM revisions
			WHERE item_id = $1
			ORDER BY revision_number DESC
		`, itemID)
	} else {
		rows, err = r.db.pool.Query(ctx, `
			SELECT id, item_id, revision_number, properties, file_key, file_version,
			       file_checksum, file_size, thumbnail_key, created_at, created_by, comment
			FROM revisions
			WHERE item_id = $1
			ORDER BY revision_number DESC
		`, itemID)
	}
	if err != nil {
		return nil, fmt.Errorf("querying revisions: %w", err)
	}
	defer rows.Close()

	var revisions []*Revision
	for rows.Next() {
		rev := &Revision{}
		var propsJSON []byte
		if hasStatusColumn {
			err = rows.Scan(
				&rev.ID, &rev.ItemID, &rev.RevisionNumber, &propsJSON, &rev.FileKey, &rev.FileVersion,
				&rev.FileChecksum, &rev.FileSize, &rev.FileStorageBackend,
				&rev.ThumbnailKey, &rev.CreatedAt, &rev.CreatedBy, &rev.Comment,
				&rev.Status, &rev.Labels,
			)
		} else {
			err = rows.Scan(
				&rev.ID, &rev.ItemID, &rev.RevisionNumber, &propsJSON, &rev.FileKey, &rev.FileVersion,
				&rev.FileChecksum, &rev.FileSize, &rev.ThumbnailKey, &rev.CreatedAt, &rev.CreatedBy, &rev.Comment,
			)
			rev.Status = "draft"
			rev.Labels = []string{}
			rev.FileStorageBackend = "minio"
		}
		if err != nil {
			return nil, fmt.Errorf("scanning revision: %w", err)
		}
		if err := json.Unmarshal(propsJSON, &rev.Properties); err != nil {
			return nil, fmt.Errorf("unmarshaling properties: %w", err)
		}
		revisions = append(revisions, rev)
	}

	return revisions, nil
}

// GetRevision retrieves a specific revision by item ID and revision number.
func (r *ItemRepository) GetRevision(ctx context.Context, itemID string, revisionNumber int) (*Revision, error) {
	// Check if status column exists (migration 007 applied)
	var hasStatusColumn bool
	err := r.db.pool.QueryRow(ctx, `
		SELECT EXISTS (
			SELECT 1 FROM information_schema.columns
			WHERE table_name = 'revisions' AND column_name = 'status'
		)
	`).Scan(&hasStatusColumn)
	if err != nil {
		return nil, fmt.Errorf("checking schema: %w", err)
	}

	rev := &Revision{}
	var propsJSON []byte

	if hasStatusColumn {
		err = r.db.pool.QueryRow(ctx, `
			SELECT id, item_id, revision_number, properties, file_key, file_version,
			       file_checksum, file_size, COALESCE(file_storage_backend, 'minio'),
			       thumbnail_key, created_at, created_by, comment,
			       COALESCE(status, 'draft') as status, COALESCE(labels, ARRAY[]::TEXT[]) as labels
			FROM revisions
			WHERE item_id = $1 AND revision_number = $2
		`, itemID, revisionNumber).Scan(
			&rev.ID, &rev.ItemID, &rev.RevisionNumber, &propsJSON, &rev.FileKey, &rev.FileVersion,
			&rev.FileChecksum, &rev.FileSize, &rev.FileStorageBackend,
			&rev.ThumbnailKey, &rev.CreatedAt, &rev.CreatedBy, &rev.Comment,
			&rev.Status, &rev.Labels,
		)
	} else {
		err = r.db.pool.QueryRow(ctx, `
			SELECT id, item_id, revision_number, properties, file_key, file_version,
			       file_checksum, file_size, thumbnail_key, created_at, created_by, comment
			FROM revisions
			WHERE item_id = $1 AND revision_number = $2
		`, itemID, revisionNumber).Scan(
			&rev.ID, &rev.ItemID, &rev.RevisionNumber, &propsJSON, &rev.FileKey, &rev.FileVersion,
			&rev.FileChecksum, &rev.FileSize, &rev.ThumbnailKey, &rev.CreatedAt, &rev.CreatedBy, &rev.Comment,
		)
		rev.Status = "draft"
		rev.Labels = []string{}
		rev.FileStorageBackend = "minio"
	}

	if err == pgx.ErrNoRows {
		return nil, nil
	}
	if err != nil {
		return nil, fmt.Errorf("querying revision: %w", err)
	}
	if err := json.Unmarshal(propsJSON, &rev.Properties); err != nil {
		return nil, fmt.Errorf("unmarshaling properties: %w", err)
	}
	return rev, nil
}

// UpdateRevisionStatus updates the status and/or labels of a revision.
func (r *ItemRepository) UpdateRevisionStatus(ctx context.Context, itemID string, revisionNumber int, status *string, labels []string) error {
	if status == nil && labels == nil {
		return nil // Nothing to update
	}

	if status != nil {
		// Validate status
		switch *status {
		case RevisionStatusDraft, RevisionStatusReview, RevisionStatusReleased, RevisionStatusObsolete:
			// Valid
		default:
			return fmt.Errorf("invalid status: %s", *status)
		}
	}

	// Build dynamic update query
	query := "UPDATE revisions SET "
	args := []any{}
	argNum := 1
	updates := []string{}

	if status != nil {
		updates = append(updates, fmt.Sprintf("status = $%d", argNum))
		args = append(args, *status)
		argNum++
	}

	if labels != nil {
		updates = append(updates, fmt.Sprintf("labels = $%d", argNum))
		args = append(args, labels)
		argNum++
	}

	query += updates[0]
	for i := 1; i < len(updates); i++ {
		query += ", " + updates[i]
	}

	query += fmt.Sprintf(" WHERE item_id = $%d AND revision_number = $%d", argNum, argNum+1)
	args = append(args, itemID, revisionNumber)

	result, err := r.db.pool.Exec(ctx, query, args...)
	if err != nil {
		return fmt.Errorf("updating revision: %w", err)
	}

	if result.RowsAffected() == 0 {
		return fmt.Errorf("revision not found")
	}

	return nil
}

// CompareRevisions computes the differences between two revisions.
func (r *ItemRepository) CompareRevisions(ctx context.Context, itemID string, fromRev, toRev int) (*RevisionDiff, error) {
	// Get both revisions
	from, err := r.GetRevision(ctx, itemID, fromRev)
	if err != nil {
		return nil, fmt.Errorf("getting from revision: %w", err)
	}
	if from == nil {
		return nil, fmt.Errorf("revision %d not found", fromRev)
	}

	to, err := r.GetRevision(ctx, itemID, toRev)
	if err != nil {
		return nil, fmt.Errorf("getting to revision: %w", err)
	}
	if to == nil {
		return nil, fmt.Errorf("revision %d not found", toRev)
	}

	diff := &RevisionDiff{
		FromRevision: fromRev,
		ToRevision:   toRev,
		FromStatus:   from.Status,
		ToStatus:     to.Status,
		Added:        make(map[string]any),
		Removed:      make(map[string]any),
		Changed:      make(map[string]PropertyChange),
	}

	// Check file changes
	fromChecksum := ""
	toChecksum := ""
	if from.FileChecksum != nil {
		fromChecksum = *from.FileChecksum
	}
	if to.FileChecksum != nil {
		toChecksum = *to.FileChecksum
	}
	diff.FileChanged = fromChecksum != toChecksum

	// Calculate file size difference
	if from.FileSize != nil && to.FileSize != nil {
		sizeDiff := *to.FileSize - *from.FileSize
		diff.FileSizeDiff = &sizeDiff
	}

	// Compare properties
	// Find added and changed properties
	for key, toVal := range to.Properties {
		fromVal, exists := from.Properties[key]
		if !exists {
			diff.Added[key] = toVal
		} else if !equalValues(fromVal, toVal) {
			diff.Changed[key] = PropertyChange{
				OldValue: fromVal,
				NewValue: toVal,
			}
		}
	}

	// Find removed properties
	for key, fromVal := range from.Properties {
		if _, exists := to.Properties[key]; !exists {
			diff.Removed[key] = fromVal
		}
	}

	// Clean up empty maps for cleaner JSON
	if len(diff.Added) == 0 {
		diff.Added = nil
	}
	if len(diff.Removed) == 0 {
		diff.Removed = nil
	}
	if len(diff.Changed) == 0 {
		diff.Changed = nil
	}

	return diff, nil
}

// equalValues compares two property values for equality.
func equalValues(a, b any) bool {
	// Use JSON encoding for deep comparison
	aJSON, err1 := json.Marshal(a)
	bJSON, err2 := json.Marshal(b)
	if err1 != nil || err2 != nil {
		return false
	}
	return string(aJSON) == string(bJSON)
}

// CreateRevisionFromExisting creates a new revision by copying from an existing one (rollback).
func (r *ItemRepository) CreateRevisionFromExisting(ctx context.Context, itemID string, sourceRevNumber int, comment string, createdBy *string) (*Revision, error) {
	// Get the source revision
	source, err := r.GetRevision(ctx, itemID, sourceRevNumber)
	if err != nil {
		return nil, fmt.Errorf("getting source revision: %w", err)
	}
	if source == nil {
		return nil, fmt.Errorf("source revision %d not found", sourceRevNumber)
	}

	// Create new revision with copied properties (and optionally file reference)
	newRev := &Revision{
		ItemID:             itemID,
		Properties:         source.Properties,
		FileKey:            source.FileKey,
		FileVersion:        source.FileVersion,
		FileChecksum:       source.FileChecksum,
		FileSize:           source.FileSize,
		FileStorageBackend: source.FileStorageBackend,
		ThumbnailKey:       source.ThumbnailKey,
		CreatedBy:          createdBy,
		Comment:            &comment,
	}

	// Insert the new revision
	propsJSON, err := json.Marshal(newRev.Properties)
	if err != nil {
		return nil, fmt.Errorf("marshaling properties: %w", err)
	}

	err = r.db.pool.QueryRow(ctx, `
		INSERT INTO revisions (
			item_id, revision_number, properties, file_key, file_version,
			file_checksum, file_size, file_storage_backend, thumbnail_key, created_by, comment, status
		)
		SELECT $1, current_revision + 1, $2, $3, $4, $5, $6, $7, $8, $9, $10, 'draft'
		FROM items WHERE id = $1
		RETURNING id, revision_number, created_at
	`, newRev.ItemID, propsJSON, newRev.FileKey, newRev.FileVersion,
		newRev.FileChecksum, newRev.FileSize, newRev.FileStorageBackend, newRev.ThumbnailKey, newRev.CreatedBy, newRev.Comment,
	).Scan(&newRev.ID, &newRev.RevisionNumber, &newRev.CreatedAt)
	if err != nil {
		return nil, fmt.Errorf("inserting revision: %w", err)
	}

	newRev.Status = RevisionStatusDraft
	return newRev, nil
}

// Archive soft-deletes an item.
func (r *ItemRepository) Archive(ctx context.Context, id string) error {
	_, err := r.db.pool.Exec(ctx, `
		UPDATE items SET archived_at = now() WHERE id = $1
	`, id)
	return err
}

// UpdateItemFields holds the fields that can be updated on an item.
type UpdateItemFields struct {
	PartNumber      string
	ItemType        string
	Description     string
	UpdatedBy       *string
	SourcingType    *string
	LongDescription *string
}

// Update modifies an item's fields. The UUID remains stable.
func (r *ItemRepository) Update(ctx context.Context, id string, fields UpdateItemFields) error {
	_, err := r.db.pool.Exec(ctx, `
		UPDATE items
		SET part_number = $2, item_type = $3, description = $4, updated_by = $5,
		    sourcing_type = COALESCE($6, sourcing_type),
		    long_description = CASE WHEN $7::boolean THEN $8 ELSE long_description END,
		    updated_at = now()
		WHERE id = $1 AND archived_at IS NULL
	`, id, fields.PartNumber, fields.ItemType, fields.Description, fields.UpdatedBy,
		fields.SourcingType,
		fields.LongDescription != nil, fields.LongDescription,
	)
	if err != nil {
		return fmt.Errorf("updating item: %w", err)
	}
	return nil
}

// SetThumbnailKey updates the thumbnail_key on an item.
func (r *ItemRepository) SetThumbnailKey(ctx context.Context, itemID string, key string) error {
	_, err := r.db.pool.Exec(ctx,
		`UPDATE items SET thumbnail_key = $1, updated_at = now() WHERE id = $2`,
		key, itemID,
	)
	if err != nil {
		return fmt.Errorf("setting thumbnail key: %w", err)
	}
	return nil
}

// Delete permanently removes an item and all its revisions.
func (r *ItemRepository) Delete(ctx context.Context, id string) error {
	_, err := r.db.pool.Exec(ctx, `
		DELETE FROM items WHERE id = $1
	`, id)
	if err != nil {
		return fmt.Errorf("deleting item: %w", err)
	}
	return nil
}

// Unarchive restores a soft-deleted item.
func (r *ItemRepository) Unarchive(ctx context.Context, id string) error {
	_, err := r.db.pool.Exec(ctx, `
		UPDATE items SET archived_at = NULL, updated_at = now() WHERE id = $1
	`, id)
	return err
}