foldermap: make folder-map syntax more expressive

Improve the folder mapping syntax so that prefixes can be removed
completely. The following line in the folder-map file

* = INBOX/*

will strip the INBOX/ prefix from all subfolders of INBOX, e.g. map
"INBOX/Project1" to "Project1".

To prevent a key collision with multiple "*" keys (the folder mapping is
stored as a map internally), a group of "*" will be condensed to one "*",
e.g.

** = INBOX/*

has the same meaning as above.

Also, adjust name translation for folder creation and add tests.

Fixes: https://todo.sr.ht/~rjarry/aerc/176
Signed-off-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>
Tested-by: Bence Ferdinandy <bence@ferdinandy.com>

3 files changed, 142 insertions, 11 deletions

diff --git a/doc/aerc-accounts.5.scd b/doc/aerc-accounts.5.scd
index 0cf7071b..6fe558cd 100644
--- a/doc/aerc-accounts.5.scd
+++ b/doc/aerc-accounts.5.scd
@@ -105,6 +105,11 @@ Note that many of these configuration options are written for you, such as
 	G = [Gmail]\*
 	```
 
+	Remove a prefix for all subfolders:
+	```
+	* = [Gmail]/\*
+	```
+
 	Remap all subfolders and avoid a folder collision:
 	```
 	Archive/existing = Archive\*
diff --git a/worker/middleware/foldermapper.go b/worker/middleware/foldermapper.go
index c78833a2..ee57b9c8 100644
--- a/worker/middleware/foldermapper.go
+++ b/worker/middleware/foldermapper.go
@@ -1,6 +1,7 @@
 package middleware
 
 import (
+	"fmt"
 	"strings"
 	"sync"
 
@@ -28,7 +29,10 @@ func NewFolderMapper(base types.WorkerInteractor, mapping map[string]string,
 func (f *folderMapper) incoming(msg types.WorkerMessage, dir string) string {
 	f.Lock()
 	defer f.Unlock()
-	mapped := f.table[dir]
+	mapped, ok := f.table[dir]
+	if !ok {
+		return dir
+	}
 	return mapped
 }
 
@@ -52,13 +56,16 @@ func (f *folderMapper) store(s string) {
 	f.Tracef("store display folder '%s' to '%s'", display, s)
 }
 
-func (f *folderMapper) create(s string) string {
+func (f *folderMapper) create(s string) (string, error) {
 	f.Lock()
 	defer f.Unlock()
-	backend := f.fm.Create(s)
+	backend := createFolder(f.table, s)
+	if _, exists := f.table[s]; exists {
+		return s, fmt.Errorf("folder already exists: %s", s)
+	}
 	f.table[s] = backend
 	f.Tracef("create display folder '%s' as '%s'", s, backend)
-	return backend
+	return backend, nil
 }
 
 func (f *folderMapper) ProcessAction(msg types.WorkerMessage) types.WorkerMessage {
@@ -74,7 +81,11 @@ func (f *folderMapper) ProcessAction(msg types.WorkerMessage) types.WorkerMessag
 	case *types.MoveMessages:
 		msg.Destination = f.incoming(msg, msg.Destination)
 	case *types.CreateDirectory:
-		msg.Directory = f.create(msg.Directory)
+		var err error
+		msg.Directory, err = f.create(msg.Directory)
+		if err != nil {
+			f.Errorf("error creating new directory: %v", err)
+		}
 	case *types.RemoveDirectory:
 		msg.Directory = f.incoming(msg, msg.Directory)
 	case *types.OpenDirectory:
@@ -105,6 +116,10 @@ func (f *folderMapper) PostMessage(msg types.WorkerMessage, cb func(m types.Work
 		case *types.OpenDirectory:
 			msg.Directory = f.outgoing(msg, msg.Directory)
 		}
+	case *types.CheckMailDirectories:
+		for i := range msg.Directories {
+			msg.Directories[i] = f.outgoing(msg, msg.Directories[i])
+		}
 	case *types.Directory:
 		f.store(msg.Dir.Name)
 		msg.Dir.Name = f.outgoing(msg, msg.Dir.Name)
@@ -130,23 +145,31 @@ func (f *folderMap) Apply(s string) string {
 			strict = false
 		}
 		if (strings.HasPrefix(s, v) && !strict) || (s == v && strict) {
-			s = k + strings.TrimPrefix(s, v)
+			term := strings.TrimPrefix(s, v)
+			if strings.Contains(k, "*") && !strict {
+				prefix := k
+				for strings.Contains(prefix, "**") {
+					prefix = strings.ReplaceAll(prefix, "**", "*")
+				}
+				s = strings.Replace(prefix, "*", term, 1)
+			} else {
+				s = k + term
+			}
 		}
 	}
 	return s
 }
 
-// Create reverses the mapping of a new folder name
-func (f *folderMap) Create(s string) string {
+// createFolder reverses the mapping of a new folder name
+func createFolder(table map[string]string, s string) string {
 	max, key := 0, ""
-	for k := range f.mapping {
+	for k := range table {
 		if strings.HasPrefix(s, k) && len(k) > max {
 			max, key = len(k), k
 		}
 	}
 	if max > 0 && key != "" {
-		s = strings.TrimSuffix(f.mapping[key], "*") +
-			strings.TrimPrefix(s, key)
+		s = table[key] + strings.TrimPrefix(s, key)
 	}
 	return s
 }
diff --git a/worker/middleware/foldermapper_test.go b/worker/middleware/foldermapper_test.go
new file mode 100644
index 00000000..0b4f6dba
--- /dev/null
+++ b/worker/middleware/foldermapper_test.go
@@ -0,0 +1,103 @@
+package middleware
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestFolderMap_Apply(t *testing.T) {
+	tests := []struct {
+		name    string
+		mapping map[string]string
+		order   []string
+		input   []string
+		want    []string
+	}{
+		{
+			name:    "strict single folder mapping",
+			mapping: map[string]string{"Drafts": "INBOX/Drafts"},
+			order:   []string{"Drafts"},
+			input:   []string{"INBOX/Drafts"},
+			want:    []string{"Drafts"},
+		},
+		{
+			name:    "prefix mapping with * suffix",
+			mapping: map[string]string{"Prefix/": "INBOX/*"},
+			order:   []string{"Prefix/"},
+			input:   []string{"INBOX", "INBOX/Test1", "INBOX/Test2", "Archive"},
+			want:    []string{"INBOX", "Prefix/Test1", "Prefix/Test2", "Archive"},
+		},
+		{
+			name:    "remove prefix with * in key",
+			mapping: map[string]string{"*": "INBOX/*"},
+			order:   []string{"*"},
+			input:   []string{"INBOX", "INBOX/Test1", "INBOX/Test2", "Archive"},
+			want:    []string{"INBOX", "Test1", "Test2", "Archive"},
+		},
+		{
+			name: "remove two prefixes with * in keys",
+			mapping: map[string]string{
+				"*":  "INBOX/*",
+				"**": "PROJECT/*",
+			},
+			order: []string{"*", "**"},
+			input: []string{"INBOX", "INBOX/Test1", "INBOX/Test2", "Archive", "PROJECT/sub1", "PROJECT/sub2"},
+			want:  []string{"INBOX", "Test1", "Test2", "Archive", "sub1", "sub2"},
+		},
+		{
+			name: "multiple, sequential mappings",
+			mapping: map[string]string{
+				"Archive/existing": "Archive*",
+				"Archive":          "Archivum*",
+			},
+			order: []string{"Archive/existing", "Archive"},
+			input: []string{"Archive", "Archive/sub", "Archivum", "Archivum/year1"},
+			want:  []string{"Archive/existing", "Archive/existing/sub", "Archive", "Archive/year1"},
+		},
+	}
+
+	for i, test := range tests {
+		fm := &folderMap{
+			mapping: test.mapping,
+			order:   test.order,
+		}
+		var result []string
+		for _, in := range test.input {
+			result = append(result, fm.Apply(in))
+		}
+		if !reflect.DeepEqual(result, test.want) {
+			t.Errorf("test (%d: %s) failed: want '%v' but got '%v'",
+				i, test.name, test.want, result)
+		}
+	}
+}
+
+func TestFolderMap_createFolder(t *testing.T) {
+	tests := []struct {
+		name  string
+		table map[string]string
+		input string
+		want  string
+	}{
+		{
+			name:  "create normal folder",
+			table: map[string]string{"Drafts": "INBOX/Drafts"},
+			input: "INBOX/Drafts2",
+			want:  "INBOX/Drafts2",
+		},
+		{
+			name:  "create mapped folder",
+			table: map[string]string{"Drafts": "INBOX/Drafts"},
+			input: "Drafts/Sub",
+			want:  "INBOX/Drafts/Sub",
+		},
+	}
+
+	for i, test := range tests {
+		result := createFolder(test.table, test.input)
+		if result != test.want {
+			t.Errorf("test (%d: %s) failed: want '%v' but got '%v'",
+				i, test.name, test.want, result)
+		}
+	}
+}