Metadata keys can have multiple values

Closes #6

environment.go

@@ -101,24 +101,24 @@ func (this *Environment) parse (name string, modTime time.Time, input io.Reader)
 	// read entire file and split into front matter and body
 	buffer, err := io.ReadAll(input)
 	if err != nil { return nil, err }
-	frontMatter, body, err := SplitMeta(string(buffer))
+	meta, body, err := SplitMeta(string(buffer))
 	if err != nil { return nil, err }
 
 	// assemble the document struct
 	document := &Document {
-		Meta:        frontMatter,
+		Meta:        meta,
 		environment: this,
 		name:        name,
 		parseTime:   time.Now(),
 		template:    template.New(name),
 	}
-	if author, ok := frontMatter["author"]; ok {
+	if author := meta.Get("author"); author != "" {
 		document.Author = author
 	}
-	if title, ok := frontMatter["title"]; ok {
+	if title := meta.Get("title"); title != "" {
 		document.Title = title
 	}
-	if extends, ok := frontMatter["extends"]; ok {
+	if extends := meta.Get("extends"); extends != "" {
 		document.Extends = extends
 	}
 

error.go

@@ -5,7 +5,6 @@ type Error string; const (
 	ErrCircularInheritance Error = "circular inheritance"
 	ErrMetaMalformed       Error = "metadata is malformed"
 	ErrMetaNeverClosed     Error = "metadata is never closed"
-	ErrMetaDuplicateKey    Error = "duplicate key in front matter"
 	ErrTypeMismatch        Error = "type mismatch"
 )
 

http/handler.go

@@ -112,10 +112,10 @@ func (this *Handler) serveDocument (
 		recorder.Reset()
 		recorder.Head = res.Header().Clone()
 	}
-	if contentType, ok := document.Meta["content-type"]; ok {
+	if contentType := document.Meta.Get("content-type"); contentType != "" {
 		recorder.Header().Set("Content-Type", contentType)
 	}
-	if status, ok := document.Meta["status"]; ok {
+	if status := document.Meta.Get("status"); status != "" {
 		if status, err := strconv.Atoi(status); err == nil {
 			recorder.Status = status
 		}

meta.go

@@ -1,6 +1,7 @@
 package step
 
 import "io"
+import "slices"
 import "strconv"
 import "strings"
 
@@ -8,7 +9,7 @@ const metaRule = "---"
 
 // Meta represents optional metadata that can occur at the very start of
 // a document.
-type Meta = map[string] string
+type Meta map[string] []string
 
 // SplitMeta parses the metadata (if it exists), returning a map representing it
 // along with the rest of the input as a string. If there is no metadata, an
@@ -52,7 +53,7 @@ func ParseMeta (input string) (Meta, error) {
 		if !ok {
 			return nil, ErrMetaMalformed
 		}
-		key   = strings.ToLower(strings.TrimSpace(key))
+		key   = strings.TrimSpace(key)
 		value = strings.TrimSpace(value)
 		if strings.HasPrefix(value, "\"") || strings.HasPrefix(value, "'") {
 			unquoted, err := strconv.Unquote(value)
@@ -64,10 +65,7 @@ func ParseMeta (input string) (Meta, error) {
 		if key == "" {
 			return nil, ErrMetaMalformed
 		}
-		if _, exists := meta[key]; exists {
-			return nil, ErrMetaDuplicateKey
-		}
-		meta[key] = value
+		meta.Add(key, value)
 	}
 	return meta, nil
 }
@@ -78,3 +76,46 @@ func DecodeMeta (input io.Reader) (Meta, error) {
 	if err != nil { return nil, err }
 	return ParseMeta(string(buffer))
 }
+
+// Add adds the key/value pair to the metadata. It appends to any existing
+// values associated with the key. The key is case insensitive.
+func (meta Meta) Add (key, value string) {
+	key = canonicalMetaKey(key)
+	meta[key] = append(meta[key], value)
+}
+
+// Clone returns a deep copy of the metadata.
+func (meta Meta) Clone () Meta {
+	clone := make(Meta, len(meta))
+	for key, value := range meta {
+		clone[key] = slices.Clone(value)
+	}
+	return clone
+}
+
+// Del deletes the values associated with the key. The key is case insensitive.
+func (meta Meta) Del (key string) {
+	key = canonicalMetaKey(key)
+	delete(meta, key)
+}
+
+// Get gets the first value associated with the key. The key is case
+// insensitive.
+func (meta Meta) Get (key string) string {
+	key = canonicalMetaKey(key)
+	slice, ok := meta[key]
+	if !ok             { return "" }
+	if len(slice) == 0 { return "" }
+	return slice[0]
+}
+
+// Set replaces all values currently associated with key with the single element
+// value. The key is case insensitive.
+func (meta Meta) Set (key, value string) {
+	key = canonicalMetaKey(key)
+	meta[key] = []string { value }
+}
+
+func canonicalMetaKey (key string) string {
+	return strings.ToLower(key)
+}

meta_test.go

@@ -13,7 +13,7 @@ theres another hr that shouldnt
 break anything
 break: anything
 `
-	frontMatter, body, err := SplitMeta(
+	meta, body, err := SplitMeta(
 `---
 FOO: baR
    fOoo: Bar
@@ -34,27 +34,27 @@ Sentence: ` + quickBrownFox + `
 	}
 	
 	test.Log("META:")
-	test.Log(frontMatter)
-	value0, ok := frontMatter["foo"]
-	if !ok { test.Fatal("missing key") }
-	value1, ok := frontMatter["fooo"]
-	if !ok { test.Fatal("missing key") }
-	value2, ok := frontMatter["shouldn't break anything"]
-	if !ok { test.Fatal("missing key") }
-	value3, ok := frontMatter["this"]
-	if !ok { test.Fatal("missing key") }
-	value4, ok := frontMatter["sentence"]
-	if !ok { test.Fatal("missing key") }
-	if value0 != "baR"         { test.Fatal("value is not correct") }
-	if value1 != "Bar"         { test.Fatal("value is not correct") }
-	if value2 != "---"         { test.Fatal("value is not correct") }
-	if value3 != "that"        { test.Fatal("value is not correct") }
-	if value4 != quickBrownFox { test.Fatal("value is not correct") }
+	test.Log(meta)
+	if meta.Get("foo") != "baR" {
+		test.Fatal("value is not correct")
+	}
+	if meta.Get("fooo") != "Bar" {
+		test.Fatal("value is not correct")
+	}
+	if meta.Get("shouldn't break anything") != "---" {
+		test.Fatal("value is not correct")
+	}
+	if meta.Get("this") != "that" {
+		test.Fatal("value is not correct")
+	}
+	if meta.Get("sentence") != quickBrownFox {
+		test.Fatal("value is not correct")
+	}
 }
 
 func TestSplitMetaCRLF (test *testing.T) {
 	correctBody := "this is some sample text\r\n---\r\ntheres another hr that shouldnt\r\nbreak anything\r\nbreak: anything\r\n"
-	frontMatter, body, err := SplitMeta(
+	meta, body, err := SplitMeta(
 "---\r\nFOO: baR\r\n   fOoo: Bar\r\nShouldn't break anything: ---\r\n\r\nthis :  that\r\nSentence: " + quickBrownFox + "\r\n---\r\n" + correctBody)
 	if err != nil {
 		test.Fatal(err)
@@ -68,22 +68,22 @@ func TestSplitMetaCRLF (test *testing.T) {
 	}
 	
 	test.Log("META:")
-	test.Log(frontMatter)
-	value0, ok := frontMatter["foo"]
-	if !ok { test.Fatal("missing key") }
-	value1, ok := frontMatter["fooo"]
-	if !ok { test.Fatal("missing key") }
-	value2, ok := frontMatter["shouldn't break anything"]
-	if !ok { test.Fatal("missing key") }
-	value3, ok := frontMatter["this"]
-	if !ok { test.Fatal("missing key") }
-	value4, ok := frontMatter["sentence"]
-	if !ok { test.Fatal("missing key") }
-	if value0 != "baR"         { test.Fatal("value is not correct") }
-	if value1 != "Bar"         { test.Fatal("value is not correct") }
-	if value2 != "---"         { test.Fatal("value is not correct") }
-	if value3 != "that"        { test.Fatal("value is not correct") }
-	if value4 != quickBrownFox { test.Fatal("value is not correct") }
+	test.Log(meta)
+	if meta.Get("foo") != "baR" {
+		test.Fatal("value is not correct")
+	}
+	if meta.Get("fooo") != "Bar" {
+		test.Fatal("value is not correct")
+	}
+	if meta.Get("shouldn't break anything") != "---" {
+		test.Fatal("value is not correct")
+	}
+	if meta.Get("this") != "that" {
+		test.Fatal("value is not correct")
+	}
+	if meta.Get("sentence") != quickBrownFox {
+		test.Fatal("value is not correct")
+	}
 }
 
 func TestParseMeta (test *testing.T) {
@@ -99,13 +99,13 @@ number: 3849
 	
 	test.Log("META:")
 	test.Log(meta)
-	value0, ok := meta["thing"]
-	if !ok { test.Fatal("missing key") }
-	value1, ok := meta["other-thing"]
-	if !ok { test.Fatal("missing key") }
-	value2, ok := meta["number"]
-	if !ok { test.Fatal("missing key") }
-	if value0 != "\tQuoted string!!!!!m   " { test.Fatal("value is not correct") }
-	if value1 != "askdjlksajd"              { test.Fatal("value is not correct") }
-	if value2 != "3849"                     { test.Fatal("value is not correct") }
+	if meta.Get("thing") != "\tQuoted string!!!!!   " {
+		test.Fatal("value is not correct")
+	}
+	if meta.Get("other-thing") != "askdjlksajd" {
+		test.Fatal("value is not correct")
+	}
+	if meta.Get("number") != "3849" {
+		test.Fatal("value is not correct")
+	}
 }