2 files changed, 289 insertions, 0 deletions
diff --git a/gui/internal/model/settings.go b/gui/internal/model/settings.go
new file mode 100644
index 0000000..7c31997
--- /dev/null
+++ b/gui/internal/model/settings.go
@@ -0,0 +1,135 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package model
+
+import (
+	"fmt"
+	"strings"
+
+	"krino/internal/sexp"
+)
+
+// DirSettings are the forms a directory file may carry above its rules, in
+// the order the form shows them. They are the settings krino.conf(5)
+// documents for a directory; anything else in the file is a rule, an
+// exclude, or not krino's (GUI design §5.1).
+var DirSettings = []string{
+	"path", "recursive", "max-depth", "min-age", "max-read", "max-size",
+	"busy", "case", "fold", "on-conflict", "ignore",
+}
+
+// Setting reads one directory setting as it is written - the form's
+// arguments, not their meaning - and whether the file sets it at all.
+func (r *Rules) Setting(head string) (args string, set bool, err error) {
+	if !isDirSetting(head) {
+		return "", false, fmt.Errorf("model: %s is not a directory setting", head)
+	}
+	node, err := r.settingNode(head)
+	if err != nil || node == nil {
+		return "", false, err
+	}
+	return argsOf(node, r.Text), true, nil
+}
+
+// SetSetting writes one directory setting: args as they are to be written,
+// or "" to take the setting out of the file. A setting already in the file
+// is rewritten where it stands; a new one goes at the end of the header,
+// above the first exclude or rule, so a directory file keeps its shape.
+// The path is the one setting that cannot be cleared - without it the file
+// does not load.
+func (r *Rules) SetSetting(head, args string) error {
+	if !isDirSetting(head) {
+		return fmt.Errorf("model: %s is not a directory setting", head)
+	}
+	args = strings.TrimSpace(args)
+	if args == "" && head == "path" {
+		return fmt.Errorf("model: a directory needs its (path ...)")
+	}
+	node, err := r.settingNode(head)
+	if err != nil {
+		return err
+	}
+	switch {
+	case node != nil && args == "":
+		start, end := r.lineSpan(node)
+		r.Text = join(r.Text[:start], r.Text[end:])
+	case node != nil:
+		r.Text = r.Text[:node.Pos.Offset] + "(" + head + " " + args + ")" + r.Text[node.End.Offset:]
+	default:
+		at, err := r.headerEnd()
+		if err != nil {
+			return err
+		}
+		r.Text = r.Text[:at] + "(" + head + " " + args + ")\n" + r.Text[at:]
+	}
+	return nil
+}
+
+// isDirSetting reports whether head is one of the directory settings.
+func isDirSetting(head string) bool {
+	for _, s := range DirSettings {
+		if s == head {
+			return true
+		}
+	}
+	return false
+}
+
+// settingNode is the form for head in the current text, or nil. A file that
+// does not parse has no settings to read.
+func (r *Rules) settingNode(head string) (*sexp.Node, error) {
+	nodes, err := sexp.Parse(r.File, []byte(r.Text))
+	if err != nil {
+		return nil, err
+	}
+	for _, n := range nodes {
+		if n.Kind == sexp.List && n.Head() == head {
+			return n, nil
+		}
+	}
+	return nil, nil
+}
+
+// headerEnd is where a new setting goes: after the last setting already
+// written, and in any case above the first exclude or rule.
+func (r *Rules) headerEnd() (int, error) {
+	nodes, err := sexp.Parse(r.File, []byte(r.Text))
+	if err != nil {
+		return 0, err
+	}
+	at := 0
+	for _, n := range nodes {
+		if n.Kind != sexp.List {
+			continue
+		}
+		switch {
+		case isDirSetting(n.Head()):
+			at = lineEnd(r.Text, n.End.Offset)
+		case n.Head() == "exclude" || n.Head() == "rule":
+			if at == 0 {
+				at = lineStart(r.Text, n.Pos.Offset)
+			}
+			return at, nil
+		}
+	}
+	if at == 0 {
+		at = len(r.Text)
+	}
+	return at, nil
+}
+
+// lineSpan is the whole line a setting is written on, so clearing it takes
+// the comment that trails it rather than leaving it to dangle.
+func (r *Rules) lineSpan(n *sexp.Node) (start, end int) {
+	return lineStart(r.Text, n.Pos.Offset), lineEnd(r.Text, n.End.Offset)
+}
+
+// argsOf is a form's arguments exactly as the file writes them.
+func argsOf(n *sexp.Node, text string) string {
+	if len(n.Children) < 2 {
+		return ""
+	}
+	from := n.Children[1].Pos.Offset
+	to := n.Children[len(n.Children)-1].End.Offset
+	return strings.TrimSpace(text[from:to])
+}
diff --git a/gui/internal/model/settings_test.go b/gui/internal/model/settings_test.go
new file mode 100644
index 0000000..46f8b75
--- /dev/null
+++ b/gui/internal/model/settings_test.go
@@ -0,0 +1,154 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package model
+
+import (
+	"strings"
+	"testing"
+)
+
+// settingsFile has a header with some settings set and others left out, and
+// comments around them that must survive every edit.
+const settingsFile = `;; the directory krino sorts
+(path "~/dl")
+(min-age 2m)                            ; leave fresh files alone
+(ignore "*.part" ".*")
+
+(rule "all"
+  (move "Out"))
+`
+
+// TestSettingReads: a directory setting is read as it is written, and one
+// that is not in the file reads as absent.
+func TestSettingReads(t *testing.T) {
+	r := openForms(t, settingsFile)
+	for _, c := range []struct {
+		head, want string
+		set        bool
+	}{
+		{"path", `"~/dl"`, true},
+		{"min-age", "2m", true},
+		{"ignore", `"*.part" ".*"`, true},
+		{"recursive", "", false},
+		{"on-conflict", "", false},
+	} {
+		got, ok, err := r.Setting(c.head)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if ok != c.set || got != c.want {
+			t.Errorf("Setting(%q) = %q, %v; want %q, %v", c.head, got, ok, c.want, c.set)
+		}
+	}
+}
+
+// TestSettingWrites: changing a setting rewrites that form and nothing
+// else; the comment on its line stays.
+func TestSettingWrites(t *testing.T) {
+	r := openForms(t, settingsFile)
+	if err := r.SetSetting("min-age", "1d"); err != nil {
+		t.Fatal(err)
+	}
+	if !strings.Contains(r.Text, "(min-age 1d)") {
+		t.Errorf("the new value is not in the file:\n%s", r.Text)
+	}
+	if strings.Contains(r.Text, "(min-age 2m)") {
+		t.Errorf("the old value is still there:\n%s", r.Text)
+	}
+	for _, keep := range []string{";; the directory krino sorts",
+		"; leave fresh files alone", `(ignore "*.part" ".*")`, `(rule "all"`} {
+		if !strings.Contains(r.Text, keep) {
+			t.Errorf("writing one setting lost %q:\n%s", keep, r.Text)
+		}
+	}
+	if diags := r.Check(); len(diags) > 0 {
+		t.Errorf("the file no longer loads: %v", diags)
+	}
+}
+
+// TestSettingAdds: a setting the file does not have is written into the
+// header, above the rules, and the file still loads.
+func TestSettingAdds(t *testing.T) {
+	r := openForms(t, settingsFile)
+	if err := r.SetSetting("on-conflict", "skip"); err != nil {
+		t.Fatal(err)
+	}
+	if !strings.Contains(r.Text, "(on-conflict skip)") {
+		t.Errorf("the setting was not written:\n%s", r.Text)
+	}
+	if strings.Index(r.Text, "(on-conflict skip)") > strings.Index(r.Text, `(rule "all"`) {
+		t.Errorf("the setting landed below the rules:\n%s", r.Text)
+	}
+	if diags := r.Check(); len(diags) > 0 {
+		t.Errorf("the file no longer loads: %v", diags)
+	}
+	got, ok, err := r.Setting("on-conflict")
+	if err != nil || !ok || got != "skip" {
+		t.Errorf("reading it back = %q, %v, %v", got, ok, err)
+	}
+}
+
+// TestSettingAddsAboveTheRules: a setting written below the rules - legal,
+// since order does not matter to krino - does not drag a new setting down
+// with it. The header is where settings go.
+func TestSettingAddsAboveTheRules(t *testing.T) {
+	r := openForms(t, "(path \"~/dl\")\n\n(rule \"all\"\n  (move \"Out\"))\n\n(min-age 2m)\n")
+	if err := r.SetSetting("on-conflict", "skip"); err != nil {
+		t.Fatal(err)
+	}
+	if strings.Index(r.Text, "(on-conflict skip)") > strings.Index(r.Text, `(rule "all"`) {
+		t.Errorf("the new setting landed below the rules:\n%s", r.Text)
+	}
+	if diags := r.Check(); len(diags) > 0 {
+		t.Errorf("the file no longer loads: %v", diags)
+	}
+}
+
+// TestSettingRemoves: clearing a setting takes its whole line, leaving the
+// rest of the header as it was.
+func TestSettingRemoves(t *testing.T) {
+	r := openForms(t, settingsFile)
+	if err := r.SetSetting("min-age", ""); err != nil {
+		t.Fatal(err)
+	}
+	if strings.Contains(r.Text, "min-age") {
+		t.Errorf("the setting is still there:\n%s", r.Text)
+	}
+	if strings.Contains(r.Text, "leave fresh files alone") {
+		t.Errorf("the comment on its line was left stranded:\n%s", r.Text)
+	}
+	if !strings.Contains(r.Text, `(path "~/dl")`) || !strings.Contains(r.Text, ";; the directory krino sorts") {
+		t.Errorf("removing one setting took more than its line:\n%s", r.Text)
+	}
+	if diags := r.Check(); len(diags) > 0 {
+		t.Errorf("the file no longer loads: %v", diags)
+	}
+	if _, ok, _ := r.Setting("min-age"); ok {
+		t.Error("the removed setting still reads as set")
+	}
+}
+
+// TestSettingRefusesThePathAway: a directory file without (path ...) does
+// not load, so clearing it is refused rather than written.
+func TestSettingRefusesThePathAway(t *testing.T) {
+	r := openForms(t, settingsFile)
+	before := r.Text
+	if err := r.SetSetting("path", ""); err == nil {
+		t.Error("clearing the path was accepted")
+	}
+	if r.Text != before {
+		t.Error("the refused edit changed the file")
+	}
+}
+
+// TestSettingRefusesAnUnknownHead: only the forms krino.conf(5) documents
+// as directory settings can be written this way.
+func TestSettingRefusesAnUnknownHead(t *testing.T) {
+	r := openForms(t, settingsFile)
+	if err := r.SetSetting("nonsense", "1"); err == nil {
+		t.Error("an unknown setting was accepted")
+	}
+	if _, _, err := r.Setting("nonsense"); err == nil {
+		t.Error("an unknown setting was read")
+	}
+}