package platform

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

	"git.casaderoll.de/michael/urbm/internal/model"
)

var arrayDiskName = regexp.MustCompile(`^disk[1-9][0-9]*$`)

func isArrayDiskPath(path string) bool {
	parts := strings.Split(strings.TrimPrefix(filepath.Clean(path), "/"), "/")
	return len(parts) >= 2 && parts[0] == "mnt" && arrayDiskName.MatchString(parts[1])
}

func mountedPaths() ([]string, error) {
	data, err := os.ReadFile("/proc/self/mountinfo")
	if err != nil {
		return nil, err
	}
	return parseMountPaths(string(data)), nil
}

func parseMountPaths(data string) []string {
	var paths []string
	unescape := strings.NewReplacer(`\040`, " ", `\011`, "\t", `\012`, "\n", `\134`, `\`)
	for _, line := range strings.Split(data, "\n") {
		fields := strings.Fields(line)
		if len(fields) >= 10 {
			paths = append(paths, unescape.Replace(fields[4]))
		}
	}
	return paths
}

func storageBrowseRoots(mounts []string) []string {
	roots := append([]string{}, browseRoots...)
	seen := make(map[string]bool)
	for _, mount := range mounts {
		if filepath.Dir(mount) == "/mnt" && isArrayDiskPath(mount) && !seen[mount] {
			roots = append(roots, mount)
			seen[mount] = true
		}
	}
	return roots
}

func pathUnder(path, root string) bool {
	return path == root || strings.HasPrefix(path, root+string(os.PathSeparator))
}

// Require an actual mount for removable disks and array sources. An empty
// directory left behind by an unmount must never become a backup destination.
func validateRsyncMounts(job model.Job, mounts []string) error {
	paths := []string{job.Rsync.Target}
	for _, source := range job.Sources {
		paths = append(paths, source.Path)
	}
	for _, path := range paths {
		clean := filepath.Clean(path)
		if !isArrayDiskPath(clean) && !pathUnder(clean, "/mnt/disks") {
			continue
		}
		resolved, err := filepath.EvalSymlinks(clean)
		if err != nil {
			return fmt.Errorf("environment: rsync disk unavailable: %s: %w", clean, err)
		}
		if !diskPathMounted(resolved, mounts) {
			return fmt.Errorf("environment: rsync disk is not mounted: %s", clean)
		}
	}
	return nil
}

func diskPathMounted(resolved string, mounts []string) bool {
	for _, mount := range mounts {
		if ((isArrayDiskPath(mount) && filepath.Dir(mount) == "/mnt") || strings.HasPrefix(mount, "/mnt/disks/")) && pathUnder(resolved, mount) {
			return true
		}
	}
	return false
}