From 2b0bd61baca0d83b31dbea7a8e1a670d30a94a22 Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@lukeshu.com>
Date: Thu, 16 Nov 2017 17:06:26 -0500
Subject: frontend: implement tag

---
 frontend.go        | 33 ++++++++++++++++++++++++++++++++-
 textproto/types.go | 42 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 74 insertions(+), 1 deletion(-)

diff --git a/frontend.go b/frontend.go
index 3319eee..c08e1b8 100644
--- a/frontend.go
+++ b/frontend.go
@@ -215,7 +215,38 @@ func (f *Frontend) parse() error {
 			// 'from' SP <commit-ish> LF
 			// 'tagger' (SP <name>)? SP LT <email> GT SP <when> LF
 			// data
-			// TODO
+			c := CmdTag{RefName: trimLinePrefix(line, "tag ")}
+
+			line, err = f.nextLine()
+			if err != nil {
+				return err
+			}
+			if !strings.HasPrefix(line, "from ") {
+				return fmt.Errorf("tag: expected from command: %v", line)
+			}
+			c.CommitIsh = trimLinePrefix(line, "from ")
+
+			line, err = f.nextLine()
+			if err != nil {
+				return err
+			}
+			if !strings.HasPrefix(line, "tagger ") {
+				return fmt.Errorf("tag: expected tagger command: %v", line)
+			}
+			c.Tagger, err = textproto.ParseUserTime(trimLinePrefix(line, "tagger "))
+			if err != nil {
+				return err
+			}
+
+			line, err = f.nextLine()
+			if err != nil {
+				return err
+			}
+			c.Data, err = parse_data(line)
+			if err != nil {
+				return err
+			}
+			f.cmd <- c
 		default:
 			return UnsupportedCommand(line)
 		}
diff --git a/textproto/types.go b/textproto/types.go
index 2109517..9a1731b 100644
--- a/textproto/types.go
+++ b/textproto/types.go
@@ -2,10 +2,13 @@ package textproto
 
 import (
 	"fmt"
+	"strconv"
 	"strings"
 	"time"
 )
 
+// BUG(lukeshu): Only supports the "raw" date format (not "rfc2822" or
+// "now")
 type UserTime struct {
 	Name  string
 	Email string
@@ -28,6 +31,45 @@ func (ut UserTime) String() string {
 	}
 }
 
+func ParseUserTime(str string) (UserTime, error) {
+	ret := UserTime{}
+	lt := strings.IndexAny(str, "<>")
+	if lt < 0 || str[lt] != '<' {
+		return ret, fmt.Errorf("Missing < in ident string: %v", str)
+	}
+	if lt > 0 {
+		if str[lt-1] != ' ' {
+			return ret, fmt.Errorf("Missing space before < in ident string: %v", str)
+		}
+		ret.Name = str[:lt-1]
+	}
+	gt := lt + 1 + strings.IndexAny(str[lt+1:], "<>")
+	if gt < lt+1 || str[gt] != '>' {
+		return ret, fmt.Errorf("Missing > in ident string: %v", str)
+	}
+	if str[gt+1] != ' ' {
+		return ret, fmt.Errorf("Missing space after > in ident string: %v", str)
+	}
+	ret.Email = str[lt+1 : gt]
+
+	strWhen := str[gt+2:]
+	sp := strings.IndexByte(strWhen, ' ')
+	if sp < 0 {
+		return ret, fmt.Errorf("missing time zone in when: %v", str)
+	}
+	sec, err := strconv.ParseInt(strWhen[:sp], 10, 64)
+	if err != nil {
+		return ret, err
+	}
+	tzt, err := time.Parse("-0700", strWhen[sp+1:])
+	if err != nil {
+		return ret, err
+	}
+	ret.Time = time.Unix(sec, 0).In(tzt.Location())
+
+	return ret, nil
+}
+
 type Mode uint32 // 18 bits
 
 var (
-- 
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