feat(app): add internal components batch 4

internal/app/ffmpeg_paths.go

@@ -0,0 +1,80 @@
+package app
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+)
+
+func normalizedFFmpegSetting(value string) string {
+	value = strings.TrimSpace(value)
+	if len(value) >= 2 && value[0] == '"' && value[len(value)-1] == '"' {
+		value = strings.TrimSpace(value[1 : len(value)-1])
+	}
+	return value
+}
+
+func automaticFFmpeg(value string) bool {
+	value = normalizedFFmpegSetting(value)
+	if runtime.GOOS == "windows" {
+		value = strings.ToLower(value)
+	}
+	return value == "" || value == "ffmpeg" || value == "ffmpeg.exe"
+}
+
+func ffmpegExecutableName() string {
+	if runtime.GOOS == "windows" {
+		return "ffmpeg.exe"
+	}
+	return "ffmpeg"
+}
+
+func ffmpegManagedDirectory() string {
+	directory := filepath.Join("bin", runtime.GOOS+"-"+runtime.GOARCH, "verified-b6.1.1")
+	if absolute, err := filepath.Abs(directory); err == nil {
+		return absolute
+	}
+	return directory
+}
+
+func ffmpegCandidates(configured, managedDirectory string) []string {
+	var candidates []string
+	seen := make(map[string]bool)
+	add := func(candidate string) {
+		path, err := exec.LookPath(candidate)
+		if err != nil {
+			return
+		}
+		path, err = filepath.Abs(path)
+		if err != nil {
+			return
+		}
+		key := path
+		if runtime.GOOS == "windows" {
+			key = strings.ToLower(key)
+		}
+		if !seen[key] {
+			seen[key] = true
+			candidates = append(candidates, path)
+		}
+	}
+	configured = normalizedFFmpegSetting(configured)
+	if !automaticFFmpeg(configured) {
+		add(configured)
+		return candidates
+	}
+	name := ffmpegExecutableName()
+	for _, directory := range filepath.SplitList(os.Getenv("PATH")) {
+		if filepath.IsAbs(directory) {
+			add(filepath.Join(directory, name))
+		}
+	}
+	for _, path := range []string{filepath.Join("bin", name), name, filepath.Join(managedDirectory, name), filepath.Join("bin", runtime.GOOS+"-"+runtime.GOARCH, name)} {
+		if absolute, err := filepath.Abs(path); err == nil {
+			add(absolute)
+		}
+	}
+	return candidates
+}