package structs

import (
	"fmt"
	"path/filepath"
	"sync"
)

// ConfigReader provides a compatible interface to the C++ ConfigReader
// It manages packet struct definitions and creates instances for specific versions
type ConfigReader struct {
	parser   *Parser
	structs  map[string][]*PacketVersion // Maps packet name to versions
	mu       sync.RWMutex
	basePath string
}

// NewConfigReader creates a new config reader
func NewConfigReader(basePath string) *ConfigReader {
	return &ConfigReader{
		parser:   NewParser(basePath),
		structs:  make(map[string][]*PacketVersion),
		basePath: basePath,
	}
}

// LoadStructs loads all packet structures from XML files
func (cr *ConfigReader) LoadStructs() error {
	// Use the structs/xml subdirectory
	xmlPath := filepath.Join(cr.basePath, "structs")
	cr.parser = NewParser(xmlPath)
	
	// Try to load all, but don't fail if directory doesn't exist
	cr.parser.LoadAll()
	
	return cr.buildVersionMap()
}

// LoadFiles loads specific XML files
func (cr *ConfigReader) LoadFiles(files []string) error {
	for _, file := range files {
		if err := cr.parser.LoadFile(file); err != nil {
			return err
		}
	}
	
	return cr.buildVersionMap()
}

// buildVersionMap builds the internal version map from loaded packets
func (cr *ConfigReader) buildVersionMap() error {
	cr.mu.Lock()
	defer cr.mu.Unlock()
	
	// Build version map
	cr.structs = make(map[string][]*PacketVersion)
	
	for _, name := range cr.parser.ListPackets() {
		def, _ := cr.parser.GetPacket(name)
		versions := make([]*PacketVersion, len(def.Versions))
		for i := range def.Versions {
			versions[i] = &def.Versions[i]
		}
		cr.structs[name] = versions
	}
	
	return nil
}

// ReloadStructs reloads all packet structures
func (cr *ConfigReader) ReloadStructs() error {
	return cr.LoadStructs()
}

// GetStruct returns a packet struct for the best matching version
// This matches the C++ ConfigReader::getStruct behavior
func (cr *ConfigReader) GetStruct(name string, version uint16) (*PacketStruct, error) {
	cr.mu.RLock()
	defer cr.mu.RUnlock()
	
	versions, exists := cr.structs[name]
	if !exists {
		return nil, fmt.Errorf("struct %s not found", name)
	}
	
	// Find the best matching version (highest version <= requested)
	var bestVersion *PacketVersion
	for _, v := range versions {
		if v.Version <= version {
			if bestVersion == nil || v.Version > bestVersion.Version {
				bestVersion = v
			}
		}
	}
	
	if bestVersion == nil {
		return nil, fmt.Errorf("no suitable version found for struct %s version %d", name, version)
	}
	
	return NewPacketStruct(bestVersion), nil
}

// GetStructByVersion returns a packet struct for an exact version match
// This matches the C++ ConfigReader::getStructByVersion behavior
func (cr *ConfigReader) GetStructByVersion(name string, version uint16) (*PacketStruct, error) {
	cr.mu.RLock()
	defer cr.mu.RUnlock()
	
	versions, exists := cr.structs[name]
	if !exists {
		return nil, fmt.Errorf("struct %s not found", name)
	}
	
	// Find exact version match
	for _, v := range versions {
		if v.Version == version {
			return NewPacketStruct(v), nil
		}
	}
	
	return nil, fmt.Errorf("struct %s with exact version %d not found", name, version)
}

// GetStructVersion returns the best matching version number for a struct
func (cr *ConfigReader) GetStructVersion(name string, version uint16) (uint16, error) {
	cr.mu.RLock()
	defer cr.mu.RUnlock()
	
	versions, exists := cr.structs[name]
	if !exists {
		return 0, fmt.Errorf("struct %s not found", name)
	}
	
	// Find the best matching version
	var bestVersion uint16
	for _, v := range versions {
		if v.Version <= version && v.Version > bestVersion {
			bestVersion = v.Version
		}
	}
	
	if bestVersion == 0 {
		return 0, fmt.Errorf("no suitable version found for struct %s version %d", name, version)
	}
	
	return bestVersion, nil
}

// ListStructs returns a list of all loaded struct names
func (cr *ConfigReader) ListStructs() []string {
	cr.mu.RLock()
	defer cr.mu.RUnlock()
	
	names := make([]string, 0, len(cr.structs))
	for name := range cr.structs {
		names = append(names, name)
	}
	return names
}

// GetVersions returns all available versions for a struct
func (cr *ConfigReader) GetVersions(name string) ([]uint16, error) {
	cr.mu.RLock()
	defer cr.mu.RUnlock()
	
	versions, exists := cr.structs[name]
	if !exists {
		return nil, fmt.Errorf("struct %s not found", name)
	}
	
	result := make([]uint16, len(versions))
	for i, v := range versions {
		result[i] = v.Version
	}
	
	return result, nil
}