42wim/matterbridge

//go:build !cgolottie

package helper

import (
    "io/ioutil"
    "os"
    "os/exec"

    "github.com/sirupsen/logrus"
)

// CanConvertTgsToX Checks whether the external command necessary for ConvertTgsToX works.
func CanConvertTgsToX() error {
    // We depend on the fact that `lottie_convert.py --help` has exit status 0.
    // Hyrum's Law predicted this, and Murphy's Law predicts that this will break eventually.
    // However, there is no alternative like `lottie_convert.py --is-properly-installed`
    cmd := exec.Command("lottie_convert.py", "--help")
    return cmd.Run()
}

// ConvertTgsToWebP convert input data (which should be tgs format) to WebP format
// This relies on an external command, which is ugly, but works.
func ConvertTgsToX(data *[]byte, outputFormat string, logger *logrus.Entry) error {
    // lottie can't handle input from a pipe, so write to a temporary file:
    tmpInFile, err := ioutil.TempFile(os.TempDir(), "matterbridge-lottie-input-*.tgs")
    if err != nil {
        return err
    }
    tmpInFileName := tmpInFile.Name()
    defer func() {
        if removeErr := os.Remove(tmpInFileName); removeErr != nil {
            logger.Errorf("Could not delete temporary (input) file %s: %v", tmpInFileName, removeErr)
        }
    }()
    // lottie can handle writing to a pipe, but there is no way to do that platform-independently.
    // "/dev/stdout" won't work on Windows, and "-" upsets Cairo for some reason. So we need another file:
    tmpOutFile, err := ioutil.TempFile(os.TempDir(), "matterbridge-lottie-output-*.data")
    if err != nil {
        return err
    }
    tmpOutFileName := tmpOutFile.Name()
    defer func() {
        if removeErr := os.Remove(tmpOutFileName); removeErr != nil {
            logger.Errorf("Could not delete temporary (output) file %s: %v", tmpOutFileName, removeErr)
        }
    }()

    if _, writeErr := tmpInFile.Write(*data); writeErr != nil {
        return writeErr
    }
    // Must close before calling lottie to avoid data races:
    if closeErr := tmpInFile.Close(); closeErr != nil {
        return closeErr
    }

    // Call lottie to transform:
    cmd := exec.Command("lottie_convert.py", "--input-format", "lottie", "--output-format", outputFormat, tmpInFileName, tmpOutFileName)
    cmd.Stdout = nil
    cmd.Stderr = nil
    // NB: lottie writes progress into to stderr in all cases.
    _, stderr := cmd.Output()
    if stderr != nil {
        // 'stderr' already contains some parts of Stderr, because it was set to 'nil'.
        return stderr
    }
    dataContents, err := ioutil.ReadFile(tmpOutFileName)
    if err != nil {
        return err
    }

    *data = dataContents
    return nil
}

func SupportsFormat(format string) bool {
    switch format {
    case "png":
        fallthrough
    case "webp":
        return true
    default:
        return false
    }
    return false
}

func LottieBackend() string {
    return "lottie_convert.py"
}