From 10cf7f06c68db5ce89bb73f9222e6fdb8fb513b9 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Fri, 9 Sep 2022 19:47:30 +0530
Subject: [PATCH] Code to get file/dir completion candidates for a prefix

---
 tools/completion/files.go      | 56 ++++++++++++++++++++++++
 tools/completion/files_test.go | 79 ++++++++++++++++++++++++++++++++++
 2 files changed, 135 insertions(+)
 create mode 100644 tools/completion/files.go
 create mode 100644 tools/completion/files_test.go

diff --git a/tools/completion/files.go b/tools/completion/files.go
new file mode 100644
index 000000000..1e20f478b
--- /dev/null
+++ b/tools/completion/files.go
@@ -0,0 +1,56 @@
+// License: GPLv3 Copyright: 2022, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package completion
+
+import (
+	"fmt"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+var _ = fmt.Print
+
+type CompleteFilesCallback func(completion_candidate string, abspath string, d fs.DirEntry) error
+
+func complete_files(prefix string, callback CompleteFilesCallback) error {
+	base := "."
+	base_len := len(base) + 1
+	has_cwd_prefix := strings.HasPrefix(prefix, "./")
+	is_abs_path := filepath.IsAbs(prefix)
+	wd := ""
+	if is_abs_path {
+		base = prefix
+		base_len = 0
+		if s, err := os.Stat(prefix); err != nil || !s.IsDir() {
+			base = filepath.Dir(prefix)
+		}
+	} else {
+		wd, _ = os.Getwd()
+	}
+	filepath.WalkDir(base, func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return nil
+		}
+		if path == base {
+			return nil
+		}
+		completion_candidate := path
+		abspath := path
+		if is_abs_path {
+			completion_candidate = path[base_len:]
+		} else {
+			abspath = filepath.Join(wd, path)
+			if has_cwd_prefix {
+				completion_candidate = "./" + completion_candidate
+			}
+		}
+		if strings.HasPrefix(completion_candidate, prefix) {
+			return callback(completion_candidate, abspath, d)
+		}
+		return nil
+	})
+
+	return nil
+}
diff --git a/tools/completion/files_test.go b/tools/completion/files_test.go
new file mode 100644
index 000000000..3cdcff754
--- /dev/null
+++ b/tools/completion/files_test.go
@@ -0,0 +1,79 @@
+// License: GPLv3 Copyright: 2022, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package completion
+
+import (
+	"fmt"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"reflect"
+	"sort"
+	"testing"
+)
+
+func TestCompleteFiles(t *testing.T) {
+	tdir := t.TempDir()
+	cwd, _ := os.Getwd()
+	if cwd != "" {
+		defer os.Chdir(cwd)
+	}
+	os.Chdir(tdir)
+	os.Create(filepath.Join(tdir, "one.txt"))
+	os.Create(filepath.Join(tdir, "two.txt"))
+	os.Mkdir(filepath.Join(tdir, "odir"), 0700)
+	os.Create(filepath.Join(tdir, "odir", "three.txt"))
+	os.Create(filepath.Join(tdir, "odir", "four.txt"))
+
+	test_candidates := func(prefix string, expected ...string) {
+		if expected == nil {
+			expected = make([]string, 0)
+		}
+		sort.Strings(expected)
+		actual := make([]string, 0, len(expected))
+		complete_files(prefix, func(completion_candidate string, abspath string, d fs.DirEntry) error {
+			actual = append(actual, completion_candidate)
+			if _, err := os.Stat(abspath); err != nil {
+				t.Fatalf("Abspath does not exist: %#v", abspath)
+				return fmt.Errorf("abspath does not exist")
+			}
+			return nil
+		})
+		sort.Strings(actual)
+		if !reflect.DeepEqual(expected, actual) {
+			t.Fatalf("Did not get expected completion candidates for prefix: %#v\nExpected: %#v\nActual:   %#v", prefix, expected, actual)
+		}
+	}
+
+	test_abs_candidates := func(prefix string, expected ...string) {
+		e := make([]string, len(expected))
+		for i, x := range expected {
+			e[i] = filepath.Join(tdir, x)
+		}
+		test_candidates(prefix, e...)
+	}
+
+	test_cwd_prefix := func(prefix string, expected ...string) {
+		e := make([]string, len(expected))
+		for i, x := range expected {
+			e[i] = "./" + x
+		}
+		test_candidates("./"+prefix, e...)
+	}
+
+	test_cwd_prefix("", "one.txt", "two.txt", "odir", "odir/three.txt", "odir/four.txt")
+	test_cwd_prefix("t", "two.txt")
+	test_cwd_prefix("x")
+
+	test_abs_candidates(tdir, "one.txt", "two.txt", "odir", "odir/three.txt", "odir/four.txt")
+	test_abs_candidates(filepath.Join(tdir, "o"), "one.txt", "odir", "odir/three.txt", "odir/four.txt")
+
+	test_candidates("", "one.txt", "two.txt", "odir", "odir/three.txt", "odir/four.txt")
+	test_candidates("t", "two.txt")
+	test_candidates("o", "one.txt", "odir", "odir/three.txt", "odir/four.txt")
+	test_candidates("odir", "odir", "odir/three.txt", "odir/four.txt")
+	test_candidates("odir/", "odir/three.txt", "odir/four.txt")
+	test_candidates("odir/f", "odir/four.txt")
+	test_candidates("x")
+
+}