//go:build linux || freebsd
// +build linux freebsd

package metalink

import (
	"encoding/xml"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"sort"
	"strings"
)

// Metalink represents a metalink file (RFC 5854)
type Metalink struct {
	XMLName xml.Name `xml:"metalink"`
	XMLNS   string   `xml:"xmlns,attr"`
	Version string   `xml:"version,attr,omitempty"`

	// Original URL of the metalink
	OriginURL string `xml:"-"`

	// Files to download
	Files []File `xml:"file"`
}

// File represents a single file in a metalink
type File struct {
	Name string `xml:"name,attr"`
	Size int64  `xml:"size,attr,omitempty"`

	// Identifiers
	MetaURL MetaURL `xml:"metaurl,omitempty"`
	URLs    []URL   `xml:"url"`

	// Hashes for verification
	Hashes []Hash `xml:"hash"`

	// Language preferences
	Lang string `xml:"lang,attr,omitempty"`

	// Localized names
	LocalName []LocalName `xml:"localname,omitempty"`

	// Description
	Desc string `xml:"desc,omitempty"`

	// Patches and signatures
	Patches    []Patch     `xml:"patch,omitempty"`
	Signatures []Signature `xml:"signature,omitempty"`
}

// MetaURL links to another metalink (for mirror selection)
type MetaURL struct {
	URL      string `xml:",chardata"`
	Mediator string `xml:"mediator,attr,omitempty"`
	Priority int    `xml:"priority,attr,omitempty"`
	Location string `xml:"location,attr,omitempty"`
	Type     string `xml:"type,attr"`
}

// URL represents a single source for download
type URL struct {
	URL      string `xml:",chardata"`
	Location string `xml:"location,attr,omitempty"` // Geographic location
	Priority int    `xml:"priority,attr,omitempty"` // 1-100, lower = higher priority
	MaxConn  int    `xml:"max-connections,attr,omitempty"`
	Type     string `xml:"type,attr,omitempty"`
}

// Hash represents a checksum for verification
type Hash struct {
	Value string `xml:",chardata"`
	Type  string `xml:"type,attr"` // sha-256, sha-512, md5, etc.
}

// LocalName localized name of the file
type LocalName struct {
	Name string `xml:",chardata"`
	Lang string `xml:"xml:lang,attr"`
}

// Patch information for updating
type Patch struct {
	URL     string `xml:"url,attr"`
	MetaURL string `xml:"metaurl,attr,omitempty"`
	Size    int64  `xml:"size,attr"`
	Hash    Hash   `xml:"hash,omitempty"`
}

// Signature PGP/GPG signature
type Signature struct {
	Value string `xml:",chardata"`
	Type  string `xml:"type,attr"` // pgp, smime, etc.
}

// Parse parses a metalink file
func Parse(r io.Reader) (*Metalink, error) {
	var ml Metalink
	decoder := xml.NewDecoder(r)
	if err := decoder.Decode(&ml); err != nil {
		return nil, fmt.Errorf("failed to parse metalink: %w", err)
	}
	return &ml, nil
}

// ParseFile parses a metalink from a file
func ParseFile(path string) (*Metalink, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, fmt.Errorf("failed to open metalink file: %w", err)
	}
	defer f.Close()

	ml, err := Parse(f)
	if err != nil {
		return nil, err
	}

	ml.OriginURL = path
	return ml, nil
}

// ParseURL fetches and parses a metalink from a URL
func ParseURL(urlStr string) (*Metalink, error) {
	resp, err := http.Get(urlStr)
	if err != nil {
		return nil, fmt.Errorf("failed to fetch metalink url: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("metalink url returned status %s", resp.Status)
	}

	ml, err := Parse(resp.Body)
	if err != nil {
		return nil, err
	}

	ml.OriginURL = urlStr
	return ml, nil
}

// GetFiles returns all files from the metalink
func (m *Metalink) GetFiles() []File {
	return m.Files
}

// GetFileByName finds a file by name
func (m *Metalink) GetFileByName(name string) *File {
	for i := range m.Files {
		if m.Files[i].Name == name {
			return &m.Files[i]
		}
	}
	return nil
}

// GetURLs returns all URLs for the file sorted by priority
func (f *File) GetURLs() []URL {
	// Sort by priority (lower = higher priority)
	sorted := make([]URL, len(f.URLs))
	copy(sorted, f.URLs)

	sort.Slice(sorted, func(i, j int) bool {
		if sorted[i].Priority == 0 {
			sorted[i].Priority = 50 // Default priority
		}
		if sorted[j].Priority == 0 {
			sorted[j].Priority = 50
		}
		return sorted[i].Priority < sorted[j].Priority
	})

	return sorted
}

// GetBestURL returns the URL with the highest priority
func (f *File) GetBestURL() *URL {
	urls := f.GetURLs()
	if len(urls) == 0 {
		return nil
	}
	return &urls[0]
}

// GetHash gets a hash of the given type
func (f *File) GetHash(hashType string) string {
	for _, h := range f.Hashes {
		if strings.EqualFold(h.Type, hashType) {
			return h.Value
		}
	}
	return ""
}

// GetSHA256 returns the SHA-256 hash
func (f *File) GetSHA256() string {
	return f.GetHash("sha-256")
}

// GetSHA512 returns the SHA-512 hash
func (f *File) GetSHA512() string {
	return f.GetHash("sha-512")
}

// GetMD5 returns the MD5 hash
func (f *File) GetMD5() string {
	return f.GetHash("md5")
}

// HasHash checks if file has a hash of given type
func (f *File) HasHash(hashType string) bool {
	return f.GetHash(hashType) != ""
}

// GetSize returns the size of the file
func (f *File) GetSize() int64 {
	return f.Size
}

// IsValid checks whether the file has at least one URL
func (f *File) IsValid() bool {
	return len(f.URLs) > 0 || f.MetaURL.URL != ""
}

// GetURLsByLocation returns URLs filtered by location
func (f *File) GetURLsByLocation(location string) []URL {
	var result []URL
	for _, u := range f.URLs {
		if u.Location == "" || strings.EqualFold(u.Location, location) {
			result = append(result, u)
		}
	}
	return result
}

// GetURLsByType returns URLs of the given type (http, https, ftp, etc.)
func (f *File) GetURLsByType(urlType string) []URL {
	var result []URL
	for _, u := range f.URLs {
		if u.Type == "" || strings.EqualFold(u.Type, urlType) {
			result = append(result, u)
		}
	}
	return result
}

// GetAllURLs returns all URLs from all files
func (m *Metalink) GetAllURLs() []DownloadSource {
	var sources []DownloadSource

	for _, file := range m.Files {
		for _, u := range file.URLs {
			sources = append(sources, DownloadSource{
				FileName: file.Name,
				URL:      u.URL,
				Priority: u.Priority,
				Size:     file.Size,
				Hashes:   file.Hashes,
			})
		}
	}

	return sources
}

// DownloadSource represents a single source for download
type DownloadSource struct {
	FileName string
	URL      string
	Priority int
	Size     int64
	Hashes   []Hash
}

// GetUniqueURLs returns unique URLs across all files
func (m *Metalink) GetUniqueURLs() []string {
	seen := make(map[string]bool)
	var result []string

	for _, file := range m.Files {
		for _, u := range file.URLs {
			if !seen[u.URL] {
				seen[u.URL] = true
				result = append(result, u.URL)
			}
		}
	}

	return result
}

// Validate checks the validity of the metalink
func (m *Metalink) Validate() error {
	if len(m.Files) == 0 {
		return fmt.Errorf("metalink contains no files")
	}

	for i, file := range m.Files {
		if file.Name == "" {
			return fmt.Errorf("file %d has no name", i)
		}
		if !file.IsValid() {
			return fmt.Errorf("file %s has no valid urls", file.Name)
		}
	}

	return nil
}

// GetTotalSize calculates the total size of all files
func (m *Metalink) GetTotalSize() int64 {
	var total int64
	for _, f := range m.Files {
		total += f.Size
	}
	return total
}

// SelectMirrors selects the best mirrors for download
func (m *Metalink) SelectMirrors(maxMirrors int, preferredLocation string) []URL {
	var allURLs []URL

	for _, file := range m.Files {
		allURLs = append(allURLs, file.GetURLs()...)
	}

	// Sort by priority
	sort.Slice(allURLs, func(i, j int) bool {
		pi := allURLs[i].Priority
		pj := allURLs[j].Priority
		if pi == 0 {
			pi = 50
		}
		if pj == 0 {
			pj = 50
		}

		// Prefer URLs matching preferred location
		if preferredLocation != "" {
			iMatch := strings.EqualFold(allURLs[i].Location, preferredLocation)
			jMatch := strings.EqualFold(allURLs[j].Location, preferredLocation)
			if iMatch && !jMatch {
				return true
			}
			if !iMatch && jMatch {
				return false
			}
		}

		return pi < pj
	})

	// Return unique URLs up to maxMirrors
	seen := make(map[string]bool)
	var result []URL

	for _, u := range allURLs {
		if !seen[u.URL] {
			seen[u.URL] = true
			result = append(result, u)
			if len(result) >= maxMirrors {
				break
			}
		}
	}

	return result
}

// IsMetalinkFile detects whether a file is a metalink by its extension
func IsMetalinkFile(path string) bool {
	lower := strings.ToLower(path)
	return strings.HasSuffix(lower, ".metalink") ||
		strings.HasSuffix(lower, ".meta4") ||
		strings.HasSuffix(lower, ".metalink4")
}

// IsMetalinkContentType detects a metalink by its Content-Type header
func IsMetalinkContentType(contentType string) bool {
	ct := strings.ToLower(contentType)
	return strings.Contains(ct, "application/metalink+xml") ||
		strings.Contains(ct, "application/metalink4+xml")
}

// ParseURLs parses a metalink from a string (for inline metalinks)
func ParseURLs(metalinkXML string) (*Metalink, error) {
	return Parse(strings.NewReader(metalinkXML))
}

// GetPreferredProtocol returns the preferred protocol from URLs
func GetPreferredProtocol(urls []URL) string {
	// Prefer HTTPS > HTTP > FTP
	protocolPriority := map[string]int{
		"https": 1,
		"http":  2,
		"ftp":   3,
		"ftps":  2,
	}

	bestProtocol := ""
	bestPriority := 999

	for _, u := range urls {
		parsed, err := url.Parse(u.URL)
		if err != nil {
			continue
		}

		prio := protocolPriority[parsed.Scheme]
		if prio == 0 {
			prio = 50 // Unknown protocol
		}

		if prio < bestPriority {
			bestPriority = prio
			bestProtocol = parsed.Scheme
		}
	}

	if bestProtocol == "" {
		return "https"
	}

	return bestProtocol
}