package engine

import (
	"context"
	"fmt"
	"strings"

	"github.com/insertr/insertr/internal/db"
	"golang.org/x/net/html"
)

// CollectionElement represents an insertr-add collection element found in HTML
type CollectionElement struct {
	Node *html.Node
}

// hasInsertrAddClass checks if node has class="insertr-add" (collection)
func (e *ContentEngine) hasInsertrAddClass(node *html.Node) bool {
	classes := GetClasses(node)
	return ContainsClass(classes, "insertr-add")
}

// processCollection handles collection detection, persistence and reconstruction
func (e *ContentEngine) processCollection(collectionNode *html.Node, collectionID, siteID string) error {
	// 1. Check if collection exists in database
	existingCollection, err := e.client.GetCollection(context.Background(), siteID, collectionID)
	collectionExists := (err == nil && existingCollection != nil)

	if !collectionExists {
		// 2. New collection: extract container HTML and create collection record
		containerHTML := e.extractOriginalTemplate(collectionNode)

		_, err := e.client.CreateCollection(context.Background(), siteID, collectionID, containerHTML, "system")
		if err != nil {
			return fmt.Errorf("failed to create collection %s: %w", collectionID, err)
		}

		// 3. Extract templates and store initial items from existing children
		err = e.extractAndStoreTemplatesAndItems(collectionNode, collectionID, siteID)
		if err != nil {
			return fmt.Errorf("failed to extract templates and items for collection %s: %w", collectionID, err)
		}

		fmt.Printf("✅ Created new collection: %s with templates and initial items\n", collectionID)
	} else {
		// 4. Existing collection: Always reconstruct from database (database is source of truth)
		err = e.reconstructCollectionItems(collectionNode, collectionID, siteID)
		if err != nil {
			return fmt.Errorf("failed to reconstruct collection %s: %w", collectionID, err)
		}

		// Optional: Show item count for feedback
		existingItems, _ := e.client.GetCollectionItems(context.Background(), siteID, collectionID)
		fmt.Printf("✅ Reconstructed collection: %s from database (%d items)\n", collectionID, len(existingItems))
	}

	return nil
}

// extractAndStoreTemplatesAndItems extracts templates and stores initial items from existing collection children
func (e *ContentEngine) extractAndStoreTemplatesAndItems(collectionNode *html.Node, collectionID, siteID string) error {
	var templateIDs []int
	templateCount := 0

	// Walk through direct children of the collection
	for child := collectionNode.FirstChild; child != nil; child = child.NextSibling {
		if child.Type == html.ElementNode {
			templateCount++
		}
	}

	// If no templates found, create a default template
	if templateCount == 0 {
		_, err := e.client.CreateCollectionTemplate(context.Background(), siteID, collectionID, "default", "<div>New item</div>", true)
		if err != nil {
			return fmt.Errorf("failed to create default template: %w", err)
		}
		fmt.Printf("✅ Created default template for collection %s\n", collectionID)
		return nil
	}

	// Create templates for each unique child structure
	templateIndex := 0
	for child := collectionNode.FirstChild; child != nil; child = child.NextSibling {
		if child.Type == html.ElementNode {
			templateName := fmt.Sprintf("template_%d", templateIndex+1)
			templateHTML := e.extractCleanTemplate(child)
			isDefault := templateIndex == 0

			template, err := e.client.CreateCollectionTemplate(context.Background(), siteID, collectionID, templateName, templateHTML, isDefault)
			if err != nil {
				return fmt.Errorf("failed to create template %s: %w", templateName, err)
			}
			templateIDs = append(templateIDs, template.TemplateID)
			templateIndex++
			fmt.Printf("✅ Created template '%s' for collection %s\n", templateName, collectionID)
		}
	}

	// Store original children as initial collection items (database-first approach)
	err := e.storeChildrenAsCollectionItems(collectionNode, collectionID, siteID, templateIDs)
	if err != nil {
		return fmt.Errorf("failed to store initial collection items: %w", err)
	}

	// Clear HTML children and reconstruct from database (ensures consistency)
	err = e.reconstructCollectionItems(collectionNode, collectionID, siteID)
	if err != nil {
		return fmt.Errorf("failed to reconstruct initial collection items: %w", err)
	}

	return nil
}

// reconstructCollectionItems rebuilds collection items from database and adds them to DOM
func (e *ContentEngine) reconstructCollectionItems(collectionNode *html.Node, collectionID, siteID string) error {
	// Get all items for this collection from database
	items, err := e.client.GetCollectionItems(context.Background(), siteID, collectionID)
	if err != nil {
		return fmt.Errorf("failed to get collection items: %w", err)
	}

	// Get templates for this collection
	templates, err := e.client.GetCollectionTemplates(context.Background(), siteID, collectionID)
	if err != nil {
		return fmt.Errorf("failed to get collection templates: %w", err)
	}

	// Build template lookup for efficiency
	templateLookup := make(map[int]*db.CollectionTemplateItem)
	for _, template := range templates {
		templateLookup[template.TemplateID] = &template
	}

	// Clear existing children from the collection node
	for child := collectionNode.FirstChild; child != nil; {
		next := child.NextSibling
		collectionNode.RemoveChild(child)
		child = next
	}

	// Reconstruct items in order from database
	for _, item := range items {
		_, exists := templateLookup[item.TemplateID]
		if !exists {
			fmt.Printf("⚠️ Template %d not found for item %s, skipping\n", item.TemplateID, item.ItemID)
			continue
		}

		// Parse the stored structural template HTML
		structuralDoc, err := html.Parse(strings.NewReader(item.HTMLContent))
		if err != nil {
			fmt.Printf("⚠️ Failed to parse structural template for item %s: %v\n", item.ItemID, err)
			continue
		}

		// Find the body and extract its children (stored as complete structure)
		var structuralChild *html.Node
		e.walkNodes(structuralDoc, func(n *html.Node) {
			if n.Type == html.ElementNode && n.Data == "body" {
				// Get the first element child of body
				for child := n.FirstChild; child != nil; child = child.NextSibling {
					if child.Type == html.ElementNode {
						structuralChild = child
						break
					}
				}
			}
		})

		if structuralChild != nil {
			// Remove from its current parent before adding to collection
			if structuralChild.Parent != nil {
				structuralChild.Parent.RemoveChild(structuralChild)
			}

			// Add hydrated structural elements directly to collection (stored HTML has complete structure)
			// The structural template already contains hydrated content from database

			// Inject data-item-id attribute for collection item identification
			if structuralChild.Type == html.ElementNode {
				SetAttribute(structuralChild, "data-item-id", item.ItemID)
			}

			collectionNode.AppendChild(structuralChild)
		}
	}

	fmt.Printf("✅ Reconstructed %d items for collection %s\n", len(items), collectionID)
	return nil
}

// processChildElementsAsContent processes .insertr elements within a collection child and stores them as individual content
func (e *ContentEngine) processChildElementsAsContent(childElement *html.Node, siteID, itemID string) ([]ContentEntry, error) {
	var contentEntries []ContentEntry

	// Walk through the child element and find .insertr elements
	e.walkNodes(childElement, func(n *html.Node) {
		if n.Type == html.ElementNode && e.hasClass(n, "insertr") {
			// Generate content ID for this .insertr element
			contentID := e.idGenerator.Generate(n, "collection-item")

			// Extract the content
			htmlContent := e.extractHTMLContent(n)
			template := e.extractCleanTemplate(n)

			// Store content entry
			contentEntries = append(contentEntries, ContentEntry{
				ID:          contentID,
				SiteID:      siteID,
				HTMLContent: htmlContent,
				Template:    template,
			})

			// Set the data-content-id attribute
			SetAttribute(n, "data-content-id", contentID)

			// Clear content - this will be hydrated during reconstruction
			for child := n.FirstChild; child != nil; {
				next := child.NextSibling
				n.RemoveChild(child)
				child = next
			}
		}
	})

	return contentEntries, nil
}

// generateStructuralTemplateFromChild creates a structural template with placeholders for content
func (e *ContentEngine) generateStructuralTemplateFromChild(childElement *html.Node, contentEntries []ContentEntry) (string, error) {
	// Clone the child to avoid modifying the original
	clonedChild := e.cloneNode(childElement)

	// Walk through and replace .insertr content with data-content-id attributes
	entryIndex := 0
	e.walkNodes(clonedChild, func(n *html.Node) {
		if n.Type == html.ElementNode && e.hasClass(n, "insertr") {
			if entryIndex < len(contentEntries) {
				// Set the data-content-id attribute
				SetAttribute(n, "data-content-id", contentEntries[entryIndex].ID)

				// Clear content - this will be hydrated during reconstruction
				for child := n.FirstChild; child != nil; {
					next := child.NextSibling
					n.RemoveChild(child)
					child = next
				}

				entryIndex++
			}
		}
	})

	// Generate HTML for the structural template
	var buf strings.Builder
	if err := html.Render(&buf, clonedChild); err != nil {
		return "", fmt.Errorf("failed to render structural template: %w", err)
	}

	return buf.String(), nil
}

// createVirtualElementFromTemplate creates a virtual DOM element from template HTML
func (e *ContentEngine) createVirtualElementFromTemplate(templateHTML string) (*html.Node, error) {
	// Parse template HTML into a virtual DOM
	templateDoc, err := html.Parse(strings.NewReader(templateHTML))
	if err != nil {
		return nil, fmt.Errorf("failed to parse template HTML: %w", err)
	}

	// Find the first element in the body
	var templateElement *html.Node
	e.walkNodes(templateDoc, func(n *html.Node) {
		if templateElement == nil && n.Type == html.ElementNode && n.Data != "html" && n.Data != "head" && n.Data != "body" {
			templateElement = n
		}
	})

	if templateElement == nil {
		return nil, fmt.Errorf("no valid element found in template HTML")
	}

	return templateElement, nil
}

// CreateCollectionItemFromTemplate creates a collection item using the unified engine approach
func (e *ContentEngine) CreateCollectionItemFromTemplate(
	siteID, collectionID string,
	templateID int,
	templateHTML string,
	lastEditedBy string,
) (*db.CollectionItemWithTemplate, error) {
	// Create virtual element from template for ID generation
	virtualElement, err := e.createVirtualElementFromTemplate(templateHTML)
	if err != nil {
		return nil, fmt.Errorf("failed to create virtual element: %w", err)
	}

	// Generate unique item ID using unified generator with collection context
	itemID := e.idGenerator.Generate(virtualElement, "collection-item")

	// Process any .insertr elements within the template and store as content
	contentEntries, err := e.processChildElementsAsContent(virtualElement, siteID, itemID)
	if err != nil {
		return nil, fmt.Errorf("failed to process child elements: %w", err)
	}

	// Store individual content entries in content table
	for _, entry := range contentEntries {
		_, err := e.client.CreateContent(context.Background(), entry.SiteID, entry.ID, entry.HTMLContent, entry.Template, lastEditedBy)
		if err != nil {
			return nil, fmt.Errorf("failed to create content entry %s: %w", entry.ID, err)
		}
	}

	// Generate structural template for the collection item
	structuralTemplate, err := e.generateStructuralTemplateFromChild(virtualElement, contentEntries)
	if err != nil {
		return nil, fmt.Errorf("failed to generate structural template: %w", err)
	}

	// Create collection item with structural template
	collectionItem, err := e.client.CreateCollectionItem(context.Background(),
		siteID, collectionID, itemID, templateID, structuralTemplate, 0, lastEditedBy,
	)
	if err != nil {
		return nil, fmt.Errorf("failed to create collection item: %w", err)
	}

	return collectionItem, nil
}

// storeChildrenAsCollectionItems stores HTML children as collection items in database
func (e *ContentEngine) storeChildrenAsCollectionItems(collectionNode *html.Node, collectionID, siteID string, templateIDs []int) error {
	var childElements []*html.Node

	// Walk through direct children of the collection
	for child := collectionNode.FirstChild; child != nil; child = child.NextSibling {
		if child.Type == html.ElementNode {
			childElements = append(childElements, child)
		}
	}

	if len(childElements) == 0 {
		fmt.Printf("ℹ️ No children found to store as collection items for %s\n", collectionID)
		return nil
	}

	// Store each child as a collection item
	for i, childElement := range childElements {
		// Use corresponding template ID, or default to first template
		templateID := templateIDs[0] // Default to first template
		if i < len(templateIDs) {
			templateID = templateIDs[i]
		}

		// Generate item ID using unified generator with collection context
		itemID := e.idGenerator.Generate(childElement, "collection-item")

		// Process any .insertr elements within this child and store as content
		contentEntries, err := e.processChildElementsAsContent(childElement, siteID, itemID)
		if err != nil {
			return fmt.Errorf("failed to process child elements: %w", err)
		}

		// Store individual content entries in content table
		for _, entry := range contentEntries {
			_, err := e.client.CreateContent(context.Background(), entry.SiteID, entry.ID, entry.HTMLContent, entry.Template, "system")
			if err != nil {
				return fmt.Errorf("failed to create content entry %s: %w", entry.ID, err)
			}
		}

		// Generate structural template for this collection item
		structuralTemplate, err := e.generateStructuralTemplateFromChild(childElement, contentEntries)
		if err != nil {
			return fmt.Errorf("failed to generate structural template: %w", err)
		}

		// Store structural template in collection_items (content lives in content table)
		_, err = e.client.CreateCollectionItem(context.Background(), siteID, collectionID, itemID, templateID, structuralTemplate, i+1, "system")
		if err != nil {
			return fmt.Errorf("failed to create collection item %s: %w", itemID, err)
		}

		fmt.Printf("✅ Stored initial collection item: %s (template %d) with %d content entries\n", itemID, templateID, len(contentEntries))
	}

	return nil
}

// collectionProcessor handles collection-specific processing logic
type collectionProcessor struct {
	engine *ContentEngine
}

// newCollectionProcessor creates a collection processor
func (e *ContentEngine) newCollectionProcessor() *collectionProcessor {
	return &collectionProcessor{engine: e}
}

// process handles the full collection processing workflow
func (cp *collectionProcessor) process(collectionNode *html.Node, collectionID, siteID string) error {
	return cp.engine.processCollection(collectionNode, collectionID, siteID)
}

// extractAndStoreTemplatesAndItems delegates to engine method
func (cp *collectionProcessor) extractAndStoreTemplatesAndItems(collectionNode *html.Node, collectionID, siteID string) error {
	return cp.engine.extractAndStoreTemplatesAndItems(collectionNode, collectionID, siteID)
}

// reconstructItems delegates to engine method
func (cp *collectionProcessor) reconstructItems(collectionNode *html.Node, collectionID, siteID string) error {
	return cp.engine.reconstructCollectionItems(collectionNode, collectionID, siteID)
}

// cloneNode creates a deep copy of an HTML node
func (e *ContentEngine) cloneNode(node *html.Node) *html.Node {
	cloned := &html.Node{
		Type:      node.Type,
		Data:      node.Data,
		DataAtom:  node.DataAtom,
		Namespace: node.Namespace,
	}

	// Clone attributes
	for _, attr := range node.Attr {
		cloned.Attr = append(cloned.Attr, html.Attribute{
			Namespace: attr.Namespace,
			Key:       attr.Key,
			Val:       attr.Val,
		})
	}

	// Clone children recursively
	for child := node.FirstChild; child != nil; child = child.NextSibling {
		clonedChild := e.cloneNode(child)
		cloned.AppendChild(clonedChild)
	}

	return cloned
}