package platform

import (
	"bufio"
	"os"
	"strings"

	"gitgud.io/mike/mpv-manager/pkg/log"
)

// osReleasePaths lists the standard os-release locations, checked in order
// (/usr/lib/os-release is the fallback mandated by the os-release spec).
var osReleasePaths = []string{"/etc/os-release", "/usr/lib/os-release"}

func detectLinuxDistro() (string, string) {
	if id, idLike, _ := readOSRelease(); id != "" {
		return id, GetDistroFamily(id, idLike)
	}

	if _, err := os.Stat("/etc/redhat-release"); err == nil {
		return parseRedHatRelease()
	}

	if _, err := os.Stat("/etc/debian_version"); err == nil {
		return "debian", "debian"
	}

	log.Warn("Could not detect Linux distribution")
	return "", ""
}

// readOSRelease parses the first available os-release file and returns its
// ID, ID_LIKE, and VARIANT_ID fields (surrounding quotes stripped).
func readOSRelease() (id, idLike, variantID string) {
	for _, path := range osReleasePaths {
		file, err := os.Open(path)
		if err != nil {
			continue
		}

		scanner := bufio.NewScanner(file)
		for scanner.Scan() {
			line := scanner.Text()
			switch {
			case strings.HasPrefix(line, "ID="):
				id = strings.Trim(strings.TrimPrefix(line, "ID="), `"`)
			case strings.HasPrefix(line, "ID_LIKE="):
				idLike = strings.Trim(strings.TrimPrefix(line, "ID_LIKE="), `"`)
			case strings.HasPrefix(line, "VARIANT_ID="):
				variantID = strings.Trim(strings.TrimPrefix(line, "VARIANT_ID="), `"`)
			}
		}
		file.Close()

		return id, idLike, variantID
	}

	return "", "", ""
}

// GetLinuxDistroFamily detects the distro family by reading the system
// os-release files. Returns "" when no distribution can be identified.
func GetLinuxDistroFamily() string {
	id, idLike, _ := readOSRelease()
	if id == "" {
		return ""
	}
	return GetDistroFamily(id, idLike)
}

func parseRedHatRelease() (string, string) {
	file, err := os.ReadFile("/etc/redhat-release")
	if err != nil {
		log.Debug("Failed to read /etc/redhat-release: " + err.Error())
		return "", ""
	}
	content := string(file)
	content = strings.ToLower(content)

	switch {
	case strings.Contains(content, "fedora"):
		return "fedora", "rhel"
	case strings.Contains(content, "centos"):
		return "centos", "rhel"
	case strings.Contains(content, "red hat"):
		return "rhel", "rhel"
	default:
		return "rhel", "rhel"
	}
}

// GetDistroFamily maps an os-release ID / ID_LIKE pair to a distro family
// (debian, rhel, arch, suse). ID is matched exactly; ID_LIKE is split into
// its space-separated fields and each field is matched exactly. Unknown IDs
// are returned unchanged so callers can report them.
func GetDistroFamily(id, idLike string) string {
	id = strings.ToLower(strings.TrimSpace(id))

	debianFamily := []string{"debian", "ubuntu", "linuxmint", "mint", "pop", "elementary"}
	rhelFamily := []string{"rhel", "fedora", "centos", "redhat", "rocky", "almalinux"}
	archFamily := []string{"arch", "archlinux", "manjaro", "endeavouros", "garuda", "cachyos"}
	suseFamily := []string{"opensuse", "opensuse-leap", "opensuse-tumbleweed", "opensuse-microos", "suse", "sles"}

	matches := func(family []string) bool {
		for _, d := range family {
			if id == d {
				return true
			}
		}
		for _, like := range strings.Fields(strings.ToLower(idLike)) {
			for _, d := range family {
				if like == d {
					return true
				}
			}
		}
		return false
	}

	switch {
	case matches(debianFamily):
		return "debian"
	case matches(rhelFamily):
		return "rhel"
	case matches(archFamily):
		return "arch"
	case matches(suseFamily):
		return "suse"
	}

	return id
}