package processor

import (
	"fmt"
	"os"
	"path/filepath"
	"strconv"
	"strings"

	"github.com/antchfx/xmlquery"
	lua "github.com/yuin/gopher-lua"
)

// XMLProcessor implements the Processor interface using XPath
type XMLProcessor struct {
	Logger Logger
}

// NewXMLProcessor creates a new XMLProcessor
func NewXMLProcessor(logger Logger) *XMLProcessor {
	return &XMLProcessor{
		Logger: logger,
	}
}

// Process implements the Processor interface for XMLProcessor
func (p *XMLProcessor) Process(filename string, pattern string, luaExpr string, originalExpr string) (int, int, error) {
	// Use pattern as XPath expression
	xpathExpr := pattern

	// Read file content
	fullPath := filepath.Join(".", filename)
	content, err := os.ReadFile(fullPath)
	if err != nil {
		return 0, 0, fmt.Errorf("error reading file: %v", err)
	}

	fileContent := string(content)
	if p.Logger != nil {
		p.Logger.Printf("File %s loaded: %d bytes", fullPath, len(content))
	}

	// Process the content
	modifiedContent, modCount, matchCount, err := p.ProcessContent(fileContent, xpathExpr, luaExpr, originalExpr)
	if err != nil {
		return 0, 0, err
	}

	// If we made modifications, save the file
	if modCount > 0 {
		err = os.WriteFile(fullPath, []byte(modifiedContent), 0644)
		if err != nil {
			return 0, 0, fmt.Errorf("error writing file: %v", err)
		}

		if p.Logger != nil {
			p.Logger.Printf("Made %d XML node modifications to %s and saved (%d bytes)",
				modCount, fullPath, len(modifiedContent))
		}
	}

	return modCount, matchCount, nil
}

// ToLua implements the Processor interface for XMLProcessor
func (p *XMLProcessor) ToLua(L *lua.LState, data interface{}) error {
	// Currently not used directly as this is handled in Process
	return nil
}

// FromLua implements the Processor interface for XMLProcessor
func (p *XMLProcessor) FromLua(L *lua.LState) (interface{}, error) {
	// Currently not used directly as this is handled in Process
	return nil, nil
}

// XMLNodeToString converts an XML node to a string representation
func (p *XMLProcessor) XMLNodeToString(node *xmlquery.Node) string {
	// Use a simple string representation for now
	var sb strings.Builder

	// Start tag with attributes
	if node.Type == xmlquery.ElementNode {
		sb.WriteString("<")
		sb.WriteString(node.Data)

		// Add attributes
		for _, attr := range node.Attr {
			sb.WriteString(" ")
			sb.WriteString(attr.Name.Local)
			sb.WriteString("=\"")
			sb.WriteString(attr.Value)
			sb.WriteString("\"")
		}

		// If self-closing
		if node.FirstChild == nil {
			sb.WriteString("/>")
			return sb.String()
		}

		sb.WriteString(">")
	} else if node.Type == xmlquery.TextNode {
		// Just write the text content
		sb.WriteString(node.Data)
		return sb.String()
	} else if node.Type == xmlquery.CommentNode {
		// Write comment
		sb.WriteString("<!--")
		sb.WriteString(node.Data)
		sb.WriteString("-->")
		return sb.String()
	}

	// Add children
	for child := node.FirstChild; child != nil; child = child.NextSibling {
		sb.WriteString(p.XMLNodeToString(child))
	}

	// End tag for elements
	if node.Type == xmlquery.ElementNode {
		sb.WriteString("</")
		sb.WriteString(node.Data)
		sb.WriteString(">")
	}

	return sb.String()
}

// NodeToLuaTable creates a Lua table from an XML node
func (p *XMLProcessor) NodeToLuaTable(L *lua.LState, node *xmlquery.Node) lua.LValue {
	nodeTable := L.NewTable()

	// Add node name
	L.SetField(nodeTable, "name", lua.LString(node.Data))

	// Add node type
	switch node.Type {
	case xmlquery.ElementNode:
		L.SetField(nodeTable, "type", lua.LString("element"))
	case xmlquery.TextNode:
		L.SetField(nodeTable, "type", lua.LString("text"))
	case xmlquery.AttributeNode:
		L.SetField(nodeTable, "type", lua.LString("attribute"))
	case xmlquery.CommentNode:
		L.SetField(nodeTable, "type", lua.LString("comment"))
	default:
		L.SetField(nodeTable, "type", lua.LString("other"))
	}

	// Add node text content if it's a text node
	if node.Type == xmlquery.TextNode {
		L.SetField(nodeTable, "content", lua.LString(node.Data))
	}

	// Add attributes if it's an element node
	if node.Type == xmlquery.ElementNode && len(node.Attr) > 0 {
		attrsTable := L.NewTable()
		for _, attr := range node.Attr {
			L.SetField(attrsTable, attr.Name.Local, lua.LString(attr.Value))
		}
		L.SetField(nodeTable, "attributes", attrsTable)
	}

	// Add children if any
	if node.FirstChild != nil {
		childrenTable := L.NewTable()
		i := 1
		for child := node.FirstChild; child != nil; child = child.NextSibling {
			// Skip empty text nodes (whitespace)
			if child.Type == xmlquery.TextNode && strings.TrimSpace(child.Data) == "" {
				continue
			}

			childTable := p.NodeToLuaTable(L, child)
			childrenTable.RawSetInt(i, childTable)
			i++
		}
		L.SetField(nodeTable, "children", childrenTable)
	}

	return nodeTable
}

// GetModifiedNode retrieves a modified node from Lua
func (p *XMLProcessor) GetModifiedNode(L *lua.LState, originalNode *xmlquery.Node) (*xmlquery.Node, bool) {
	// Check if we have a node global with changes
	nodeTable := L.GetGlobal("node")
	if nodeTable == lua.LNil || nodeTable.Type() != lua.LTTable {
		return originalNode, false
	}

	// Clone the node since we don't want to modify the original
	clonedNode := *originalNode

	// For text nodes, check if content was changed
	if originalNode.Type == xmlquery.TextNode {
		contentField := L.GetField(nodeTable.(*lua.LTable), "content")
		if contentField != lua.LNil {
			if strContent, ok := contentField.(lua.LString); ok {
				if string(strContent) != originalNode.Data {
					clonedNode.Data = string(strContent)
					return &clonedNode, true
				}
			}
		}
		return originalNode, false
	}

	// For element nodes, attributes might have been changed
	if originalNode.Type == xmlquery.ElementNode {
		attrsField := L.GetField(nodeTable.(*lua.LTable), "attributes")
		if attrsField != lua.LNil && attrsField.Type() == lua.LTTable {
			attrsTable := attrsField.(*lua.LTable)

			// Check if any attributes changed
			changed := false
			for _, attr := range originalNode.Attr {
				newValue := L.GetField(attrsTable, attr.Name.Local)
				if newValue != lua.LNil {
					if strValue, ok := newValue.(lua.LString); ok {
						if string(strValue) != attr.Value {
							// Create a new attribute with the changed value
							for i, a := range clonedNode.Attr {
								if a.Name.Local == attr.Name.Local {
									clonedNode.Attr[i].Value = string(strValue)
									changed = true
								}
							}
						}
					}
				}
			}

			if changed {
				return &clonedNode, true
			}
		}
	}

	// No changes detected
	return originalNode, false
}

// SetupXMLHelpers adds XML-specific helper functions to Lua
func (p *XMLProcessor) SetupXMLHelpers(L *lua.LState) {
	// Helper function to create a new XML node
	L.SetGlobal("new_node", L.NewFunction(func(L *lua.LState) int {
		nodeName := L.CheckString(1)
		nodeTable := L.NewTable()
		L.SetField(nodeTable, "name", lua.LString(nodeName))
		L.SetField(nodeTable, "type", lua.LString("element"))
		L.SetField(nodeTable, "attributes", L.NewTable())
		L.SetField(nodeTable, "children", L.NewTable())
		L.Push(nodeTable)
		return 1
	}))

	// Helper function to set an attribute
	L.SetGlobal("set_attr", L.NewFunction(func(L *lua.LState) int {
		nodeTable := L.CheckTable(1)
		attrName := L.CheckString(2)
		attrValue := L.CheckString(3)

		attrsTable := L.GetField(nodeTable, "attributes")
		if attrsTable == lua.LNil {
			attrsTable = L.NewTable()
			L.SetField(nodeTable, "attributes", attrsTable)
		}

		L.SetField(attrsTable.(*lua.LTable), attrName, lua.LString(attrValue))
		return 0
	}))

	// Helper function to add a child node
	L.SetGlobal("add_child", L.NewFunction(func(L *lua.LState) int {
		parentTable := L.CheckTable(1)
		childTable := L.CheckTable(2)

		childrenTable := L.GetField(parentTable, "children")
		if childrenTable == lua.LNil {
			childrenTable = L.NewTable()
			L.SetField(parentTable, "children", childrenTable)
		}

		childrenTbl := childrenTable.(*lua.LTable)
		childrenTbl.RawSetInt(childrenTbl.Len()+1, childTable)
		return 0
	}))
}

// ProcessContent implements the Processor interface for XMLProcessor
// It processes XML content directly without file I/O
func (p *XMLProcessor) ProcessContent(content string, pattern string, luaExpr string, originalExpr string) (string, int, int, error) {
	// Parse the XML document
	doc, err := xmlquery.Parse(strings.NewReader(content))
	if err != nil {
		return "", 0, 0, fmt.Errorf("error parsing XML: %v", err)
	}

	// Find nodes matching XPath expression
	nodes, err := xmlquery.QueryAll(doc, pattern)
	if err != nil {
		return "", 0, 0, fmt.Errorf("invalid XPath expression: %v", err)
	}

	// Log what we found
	if p.Logger != nil {
		p.Logger.Printf("XML mode selected with XPath expression: %s (found %d matching nodes)",
			pattern, len(nodes))
	}

	if len(nodes) == 0 {
		if p.Logger != nil {
			p.Logger.Printf("No XML nodes matched XPath expression: %s", pattern)
		}
		return content, 0, 0, nil
	}

	// Initialize Lua state
	L := lua.NewState()
	defer L.Close()

	// Setup Lua helper functions
	if err := InitLuaHelpers(L); err != nil {
		return "", 0, 0, err
	}

	// Register XML-specific helper functions
	p.SetupXMLHelpers(L)

	// Track modifications
	matchCount := len(nodes)
	modificationCount := 0
	modifiedContent := content
	modifications := []ModificationRecord{}

	// Process each matching node
	for i, node := range nodes {
		// Get the original text representation of this node
		originalNodeText := p.XMLNodeToString(node)
		if p.Logger != nil {
			p.Logger.Printf("Found node #%d: %s", i+1, LimitString(originalNodeText, 100))
		}

		// For text nodes, we'll handle them directly
		if node.Type == xmlquery.TextNode && node.Parent != nil {
			// If this is a text node, we'll use its value directly
			// Get the node's text content
			textContent := node.Data

			// Set up Lua environment
			L.SetGlobal("v1", lua.LNumber(0)) // Default to 0 if not numeric
			L.SetGlobal("s1", lua.LString(textContent))

			// Try to convert to number if possible
			if floatVal, err := strconv.ParseFloat(textContent, 64); err == nil {
				L.SetGlobal("v1", lua.LNumber(floatVal))
			}

			// Execute user's Lua script
			if err := L.DoString(luaExpr); err != nil {
				if p.Logger != nil {
					p.Logger.Printf("Lua execution failed for node #%d: %v", i+1, err)
				}
				continue // Skip this node on error
			}

			// Check for modifications
			modVal := L.GetGlobal("v1")
			if v, ok := modVal.(lua.LNumber); ok {
				// If we have a numeric result, convert it to string
				newValue := strconv.FormatFloat(float64(v), 'f', -1, 64)
				if newValue != textContent {
					// Replace the node content in the document
					parentStr := p.XMLNodeToString(node.Parent)
					newParentStr := strings.Replace(parentStr, textContent, newValue, 1)
					modifiedContent = strings.Replace(modifiedContent, parentStr, newParentStr, 1)
					modificationCount++

					// Record the modification
					modifications = append(modifications, ModificationRecord{
						File:      "",
						OldValue:  textContent,
						NewValue:  newValue,
						Operation: originalExpr,
						Context:   fmt.Sprintf("(XPath: %s)", pattern),
					})

					if p.Logger != nil {
						p.Logger.Printf("Modified text node #%d: '%s' -> '%s'",
							i+1, LimitString(textContent, 30), LimitString(newValue, 30))
					}
				}
			}
			continue // Move to next node
		}

		// Convert the node to a Lua table
		nodeTable := p.NodeToLuaTable(L, node)

		// Set the node in Lua global variable for user script
		L.SetGlobal("node", nodeTable)

		// Execute user's Lua script
		if err := L.DoString(luaExpr); err != nil {
			if p.Logger != nil {
				p.Logger.Printf("Lua execution failed for node #%d: %v", i+1, err)
			}
			continue // Skip this node on error
		}

		// Get modified node from Lua
		modifiedNode, changed := p.GetModifiedNode(L, node)
		if !changed {
			if p.Logger != nil {
				p.Logger.Printf("Node #%d was not modified by script", i+1)
			}
			continue
		}

		// Render the modified node back to XML
		modifiedNodeText := p.XMLNodeToString(modifiedNode)

		// Replace just this node in the document
		if originalNodeText != modifiedNodeText {
			modifiedContent = strings.Replace(
				modifiedContent,
				originalNodeText,
				modifiedNodeText,
				1)
			modificationCount++

			// Record the modification for reporting
			modifications = append(modifications, ModificationRecord{
				File:      "",
				OldValue:  LimitString(originalNodeText, 30),
				NewValue:  LimitString(modifiedNodeText, 30),
				Operation: originalExpr,
				Context:   fmt.Sprintf("(XPath: %s)", pattern),
			})

			if p.Logger != nil {
				p.Logger.Printf("Modified node #%d", i+1)
			}
		}
	}

	if p.Logger != nil && modificationCount > 0 {
		p.Logger.Printf("Made %d XML node modifications", modificationCount)
	}

	return modifiedContent, modificationCount, matchCount, nil
}