package engine

import (
	"fmt"
	"strings"

	"golang.org/x/net/html"
)

// ContentEngine is the unified content processing engine
type ContentEngine struct {
	idGenerator *IDGenerator
	client      ContentClient
}

// NewContentEngine creates a new content processing engine
func NewContentEngine(client ContentClient) *ContentEngine {
	return &ContentEngine{
		idGenerator: NewIDGenerator(),
		client:      client,
	}
}

// ProcessContent processes HTML content according to the specified mode
func (e *ContentEngine) ProcessContent(input ContentInput) (*ContentResult, error) {
	// 1. Parse HTML
	doc, err := html.Parse(strings.NewReader(string(input.HTML)))
	if err != nil {
		return nil, fmt.Errorf("parsing HTML: %w", err)
	}

	// 2. Find insertr elements
	elements := e.findInsertrElements(doc)

	// 3. Generate IDs for elements
	generatedIDs := make(map[string]string)
	processedElements := make([]ProcessedElement, len(elements))

	for i, elem := range elements {
		// Check if element already has a data-content-id
		existingID := e.getAttribute(elem.Node, "data-content-id")
		var id string
		var wasGenerated bool

		if existingID != "" {
			// Use existing ID from enhanced element
			id = existingID
			wasGenerated = false
		} else {
			// Generate new ID for unprocessed element
			id = e.idGenerator.Generate(elem.Node, input.FilePath)
			wasGenerated = true
		}

		generatedIDs[fmt.Sprintf("element_%d", i)] = id

		processedElements[i] = ProcessedElement{
			Node:      elem.Node,
			ID:        id,
			Type:      elem.Type,
			Generated: wasGenerated,
			Tag:       elem.Node.Data,
			Classes:   GetClasses(elem.Node),
		}

		// Add/update content attributes to the node
		e.addContentAttributes(elem.Node, id, elem.Type)
	}

	// 4. Inject content if required by mode
	if input.Mode == Enhancement || input.Mode == ContentInjection {
		err = e.injectContent(processedElements, input.SiteID)
		if err != nil {
			return nil, fmt.Errorf("injecting content: %w", err)
		}
	}

	// 5. Inject editor assets for enhancement mode (development)
	if input.Mode == Enhancement {
		injector := NewInjector(e.client, input.SiteID)
		injector.InjectEditorAssets(doc, true, "")
	}

	return &ContentResult{
		Document:     doc,
		Elements:     processedElements,
		GeneratedIDs: generatedIDs,
	}, nil
}

// InsertrElement represents an insertr element found in HTML
type InsertrElement struct {
	Node *html.Node
	Type string
}

// findInsertrElements finds all elements with class="insertr"
func (e *ContentEngine) findInsertrElements(doc *html.Node) []InsertrElement {
	var elements []InsertrElement
	e.walkNodes(doc, func(n *html.Node) {
		if n.Type == html.ElementNode && e.hasInsertrClass(n) {
			elementType := e.determineContentType(n)
			elements = append(elements, InsertrElement{
				Node: n,
				Type: elementType,
			})
		}
	})
	return elements
}

// walkNodes walks through all nodes in the document
func (e *ContentEngine) walkNodes(n *html.Node, fn func(*html.Node)) {
	fn(n)
	for c := n.FirstChild; c != nil; c = c.NextSibling {
		e.walkNodes(c, fn)
	}
}

// hasInsertrClass checks if node has class="insertr"
func (e *ContentEngine) hasInsertrClass(node *html.Node) bool {
	classes := GetClasses(node)
	for _, class := range classes {
		if class == "insertr" {
			return true
		}
	}
	return false
}

// determineContentType determines the content type based on element
func (e *ContentEngine) determineContentType(node *html.Node) string {
	tag := strings.ToLower(node.Data)

	switch tag {
	case "a", "button":
		return "link"
	case "h1", "h2", "h3", "h4", "h5", "h6":
		return "text"
	case "p", "div", "section", "article", "span":
		return "markdown"
	default:
		return "text"
	}
}

// addContentAttributes adds data-content-id and data-content-type attributes
func (e *ContentEngine) addContentAttributes(node *html.Node, contentID, contentType string) {
	// Add data-content-id attribute
	e.setAttribute(node, "data-content-id", contentID)
	// Add data-content-type attribute
	e.setAttribute(node, "data-content-type", contentType)
}

// getAttribute gets an attribute value from an HTML node
func (e *ContentEngine) getAttribute(node *html.Node, key string) string {
	for _, attr := range node.Attr {
		if attr.Key == key {
			return attr.Val
		}
	}
	return ""
}

// setAttribute sets an attribute on an HTML node
func (e *ContentEngine) setAttribute(node *html.Node, key, value string) {
	// Remove existing attribute if it exists
	for i, attr := range node.Attr {
		if attr.Key == key {
			node.Attr[i].Val = value
			return
		}
	}
	// Add new attribute
	node.Attr = append(node.Attr, html.Attribute{
		Key: key,
		Val: value,
	})
}

// injectContent injects content from database into elements
func (e *ContentEngine) injectContent(elements []ProcessedElement, siteID string) error {
	for i := range elements {
		elem := &elements[i]

		// Try to get content from database
		contentItem, err := e.client.GetContent(siteID, elem.ID)
		if err != nil {
			// Content not found is not an error - element just won't have injected content
			continue
		}

		if contentItem != nil {
			// Inject the content into the element
			elem.Content = contentItem.Value
			e.injectContentIntoNode(elem.Node, contentItem.Value, contentItem.Type)
		}
	}
	return nil
}

// injectContentIntoNode injects content value into an HTML node
func (e *ContentEngine) injectContentIntoNode(node *html.Node, content, contentType string) {
	// Clear existing text content
	for child := node.FirstChild; child != nil; {
		next := child.NextSibling
		if child.Type == html.TextNode {
			node.RemoveChild(child)
		}
		child = next
	}

	// Add new text content
	textNode := &html.Node{
		Type: html.TextNode,
		Data: content,
	}
	node.AppendChild(textNode)
}