Added README, Licence, and fixed issue with modules

3 files changed, 84 insertions, 58 deletions

diff --git a/snap/fs.go b/snap/fs.go
index d0dc83d..b1cf513 100644
--- a/snap/fs.go
+++ b/snap/fs.go
@@ -5,6 +5,7 @@ import (
 	"path/filepath"
 	"os"
 	"sort"
+	"io"
 )
 
 type Snapshot struct {
@@ -36,6 +37,19 @@ func getZFSRoot(reference string) string {
 	return cursor
 }
 
+func (snap * Snapshot) tryReference(reference string) {
+	if _, err := os.Stat(reference); err != nil {
+
+		if !os.IsNotExist(err) {
+			die.Fatalf("Error encountered while attempting to read reference file in snapshot:\n%v", err)
+		}
+
+		snap.Reference = ""
+	} else {
+		snap.Reference = reference
+	}
+}
+
 func getSnapshots(reference string) []*Snapshot {
 	zfsRoot := getZFSRoot(reference)
 
@@ -43,15 +57,16 @@ func getSnapshots(reference string) []*Snapshot {
 
 	files, err := os.ReadDir(snapshotDir)
 	if err != nil {
-		die.Fatalf("Could not find the snapshots directory inside %s", snapshotDir);
+		die.Fatalf("Could not find the snapshots directory inside \"%s\"", snapshotDir);
 	}
 
 	relPath, err := filepath.Rel(zfsRoot, reference)
 	if err != nil {
-		die.Fatal("Could not find relative path to reference file: %v", err)
+		die.Fatalf("Could not find relative path to reference file: %v", err)
 	}
 
-	snaps := make([]*Snapshot, len(files))
+	n_snaps := len(files) + 1
+	snaps := make([]*Snapshot, n_snaps)
 
 	for i, file := range files {
 
@@ -68,16 +83,17 @@ func getSnapshots(reference string) []*Snapshot {
 
 		pathInSnap := filepath.Join(snapshotDir, name, relPath)
 
-		if _, err := os.Stat(pathInSnap); err != nil {
-			if !os.IsNotExist(err) {
-				die.Fatalf("Error encountered while attempting to read reference file in snapshot:\n%v", err)
-			}
-		} else {
-			snaps[i].Reference = pathInSnap
-		}
+		snaps[i].tryReference(pathInSnap)
+	}
 
+	
+	snaps[n_snaps - 1] = &Snapshot {
+		ModTime: time.Now(),
+		Name: "@",
 	}
 
+	snaps[n_snaps - 1].tryReference(reference)
+
 	return snaps
 }
 
@@ -97,6 +113,18 @@ func GetTimeseries(reference string) []*Snapshot {
 	return snaps
 }
 
+func referenceMap(snapTs []*Snapshot) []int {
+	var trimmed []int
+
+	for i, snap := range snapTs {
+		if snap.Reference != "" {
+			trimmed = append(trimmed, i)
+		}
+	}
+
+	return trimmed
+}
+
 func buildNameMap(snapTs []*Snapshot) map[string] int {
 	namemap := make(map[string] int)
 
@@ -123,15 +151,25 @@ func GetOracle(reference string) *SnapshotOracle {
 	}
 }
 
-func (oracle *SnapshotOracle) ResolveRelative(ref *Relative) string {
+func (oracle *SnapshotOracle) PathTo(ref *Relative) string {
 	n_ts := len(oracle.timeseries)
-	wanted := n_ts - 1
+	nthRef := referenceMap(oracle.timeseries)
 
-	if ref.snapshot != "" {
+	if len(nthRef) == 0 {
+		die.Fatalf("The reference file is not contained in any snapshot.")
+	}
+
+	var wanted int
+	switch (ref.snapshot) {
+	case "@":
+		wanted = nthRef[len(nthRef) - 1]
+	case "%":
+		wanted = nthRef[0]
+	default:
 		id, ok := oracle.namemap[ref.snapshot]
 
 		if !ok {
-			die.Fatal("Could not find the snapshot %s", ref.snapshot)
+			die.Fatalf("Could not find the snapshot \"%s\"", ref.snapshot)
 		}
 
 		wanted = id
@@ -144,4 +182,18 @@ func (oracle *SnapshotOracle) ResolveRelative(ref *Relative) string {
 	}
 
 	return oracle.timeseries[wanted].Reference
-}
\ No newline at end of file
+}
+
+func (oracle *SnapshotOracle) ReadAll(ref *Relative) string {
+	path := oracle.PathTo(ref)
+
+	file, err := os.Open(path)
+
+	data, err := io.ReadAll(file)
+
+	if err != nil {
+		die.Fatalf("Can't read snapshot.\n%v", err)
+	}
+
+	return string(data)
+}
diff --git a/snap/parsing.go b/snap/parsing.go
index fcacec9..0d1f09f 100644
--- a/snap/parsing.go
+++ b/snap/parsing.go
@@ -18,11 +18,6 @@ func parseEscaped(snapish string) *Relative {
 	if isEscaped(snapish) {
 		snapshot := strings.Trim(snapish, `"`);
 
-		if(snapshot == "") {
-			die.Fatal("Snapshot cannot be empty \"\"")
-		
-		}
-
 		return &Relative {
 			snapshot: snapshot,
 		}
@@ -69,7 +64,7 @@ func parseRelativeSyntax(snapish, directionToken string) *Relative {
 	}
 }
 
-func ToRelative(snapish string) * Relative {
+func toRelative(snapish string) * Relative {
 	if ref := parseEscaped(snapish); ref != nil {
 		return ref;
 	}
@@ -78,7 +73,7 @@ func ToRelative(snapish string) * Relative {
 		return ref;
 	}
 
-	if ref := parseRelativeSyntax(snapish, "^"); ref != nil {
+	if ref := parseRelativeSyntax(snapish, "-"); ref != nil {
 		ref.offset = -ref.offset;
 		return ref;
 	}
@@ -88,16 +83,26 @@ func ToRelative(snapish string) * Relative {
 	};
 }
 
-func ParseDiff(snapdiff string) (fromRel, toRel *Relative) {
-	snapishes := strings.Split(snapdiff, "..")
+func ToRelative(snapish string) * Relative {
+	rel := toRelative(snapish)
+
+	if rel.snapshot == "" {
+		die.Fatal("Please provide a snapshot. You can use @ for the current filesystem and $ for the last snapshot.")
+	}
+
+	return rel
+}
+
+func ParseDiff(snapishdiff string) (fromRel, toRel *Relative) {
+	snapishes := strings.Split(snapishdiff, "..")
 
-	if(len(snapishes) > 2) {
+	if len(snapishes) > 2 {
 		die.Fatal("Cannot diff more than two snapshots");
 	}
 
 	fromRel = ToRelative(snapishes[0])
-	toRel = &Relative{}
-	if(len(snapishes) == 2) {	
+	toRel = &Relative{snapshot: "@"}
+	if len(snapishes) == 2 {
 		toRel = ToRelative(snapishes[1])
 	}
 
diff --git a/snap/parsing_test.go b/snap/parsing_test.go
deleted file mode 100644
index 4aa232e..0000000
--- a/snap/parsing_test.go
+++ /dev/null
@@ -1,31 +0,0 @@
-package snap
-
-import "testing"
-
-func TestRelativeParsing(t * testing.T) {
-	cases := []struct {
-		snapish string
-		snapshot string
-		offset int
-	} {
-		{"snapshot", "snapshot", 0},
-		{"testing~~", "testing", -2},
-		{"%SNAPSHOT%^+++", "%SNAPSHOT%^", 3},
-		{"~~prefixed", "~~prefixed", 0},
-		{"+++", "", 3},
-		{"~~~", "", -3},
-		{"+5", "", 5},
-		{"~3", "", -3},
-		{"+", "", 1},
-		{"~", "", -1},
-		{`"~"`, "~", 0},
-	}
-
-	for _, c := range cases {
-		got := ToRelative(c.snapish)
-
-		if got.offset != c.offset || got.snapshot != c.snapshot {
-			t.Errorf("ToRelative(%s) == %+v, wanted %+v", c.snapish, got, c)
-		}
-	}
-}
\ No newline at end of file