Change the comment ID to use both bug and comment ID references.

Add comment edit command
This commit adds the comment edit command, which provides a CLI tool that allows a user to edit a comment.

1 files changed, 46 insertions, 0 deletions

diff --git a/bug/comment.go b/bug/comment.go
index 4c9d118e..1a9ca05a 100644
--- a/bug/comment.go
+++ b/bug/comment.go
@@ -1,6 +1,8 @@
 package bug
 
 import (
+	"strings"
+
 	"github.com/dustin/go-humanize"
 
 	"github.com/MichaelMure/git-bug/entity"
@@ -31,6 +33,50 @@ func (c Comment) Id() entity.Id {
 	return c.id
 }
 
+const compiledCommentIdFormat = "BCBCBCBBBCBBBBCBBBBCBBBBCBBBBCBBBBCBBBBC"
+
+// DeriveCommentId compute a merged Id for a comment holding information from
+// both the Bug's Id and the Comment's Id. This allow to later find efficiently
+// a Comment because we can access the bug directly instead of searching for a
+// Bug that has a Comment matching the Id.
+//
+// To allow the use of an arbitrary length prefix of this merged Id, Ids from Bug
+// and Comment are interleaved with this irregular pattern to give the best chance
+// to find the Comment even with a 7 character prefix.
+//
+// A complete merged Id hold 30 characters for the Bug and 10 for the Comment,
+// which give a key space of 36^30 for the Bug (~5 * 10^46) and 36^10 for the
+// Comment (~3 * 10^15). This asymmetry assume a reasonable number of Comment
+// within a Bug, while still allowing for a vast key space for Bug (that is, a
+// globally merged bug database) with a low risk of collision.
+func DeriveCommentId(bugId entity.Id, commentId entity.Id) entity.Id {
+	var id strings.Builder
+	for _, char := range compiledCommentIdFormat {
+		if char == 'B' {
+			id.WriteByte(bugId[0])
+			bugId = bugId[1:]
+		} else {
+			id.WriteByte(commentId[0])
+			commentId = commentId[1:]
+		}
+	}
+	return entity.Id(id.String())
+}
+
+func SplitCommentId(prefix string) (bugPrefix string, commentPrefix string) {
+	var bugIdPrefix strings.Builder
+	var commentIdPrefix strings.Builder
+
+	for i, char := range prefix {
+		if compiledCommentIdFormat[i] == 'B' {
+			bugIdPrefix.WriteRune(char)
+		} else {
+			commentIdPrefix.WriteRune(char)
+		}
+	}
+	return bugIdPrefix.String(), commentIdPrefix.String()
+}
+
 // FormatTimeRel format the UnixTime of the comment for human consumption
 func (c Comment) FormatTimeRel() string {
 	return humanize.Time(c.UnixTime.Time())