package release

import (
	"github.com/carlosframework/platform/internal/rootstate"
	"os"
	"path/filepath"
	"strings"
)

func GenerationFileProof(path string, before, after rootstate.FileIdentity) bool {
	if before.Same(after) {
		return true
	}
	source := func(id rootstate.FileIdentity) (string, bool) {
		root, e1 := generationProofUnescape(id.MountRoot)
		point, e2 := generationProofUnescape(id.MountPoint)
		if e1 != nil || e2 != nil || !filepath.IsAbs(root) || !filepath.IsAbs(point) || filepath.Clean(root) != root || filepath.Clean(point) != point {
			return "", false
		}
		rel, err := filepath.Rel(point, path)
		if err != nil || !filepath.IsLocal(rel) {
			return "", false
		}
		return filepath.Join(root, rel), true
	}
	if before.SameMountNamespace(after) || before.MountLineage == "" || after.MountLineage == "" || before.MountLineage == after.MountLineage || !strings.HasSuffix(before.MountLineage, "\n"+after.MountLineage) {
		return false
	}
	beforePoint, e1 := generationProofUnescape(before.MountPoint)
	afterPoint, e2 := generationProofUnescape(after.MountPoint)
	rel, err := filepath.Rel(afterPoint, beforePoint)
	if e1 != nil || e2 != nil || err != nil || rel == "." || !filepath.IsLocal(rel) {
		return false
	}
	a, ok1 := source(before)
	b, ok2 := source(after)
	if !ok1 || !ok2 || a != b {
		return false
	}
	after.MountRoot, after.MountPoint, after.MountLineage = before.MountRoot, before.MountPoint, before.MountLineage
	return before.Same(after)
}

func generationProofUnescape(s string) (string, error) {
	var out strings.Builder
	for i := 0; i < len(s); i++ {
		if s[i] != '\\' {
			out.WriteByte(s[i])
			continue
		}
		if i+3 >= len(s) {
			return "", os.ErrPermission
		}
		switch s[i : i+4] {
		case "\\040":
			out.WriteByte(' ')
		case "\\011":
			out.WriteByte('\t')
		case "\\012":
			out.WriteByte('\n')
		case "\\134":
			out.WriteByte('\\')
		default:
			return "", os.ErrPermission
		}
		i += 3
	}
	return out.String(), nil
}