Implement new Go based Desktop app

This focuses on Windows first, but coudl be used for Mac
and possibly linux in the future.

app/lifecycle/server.go

@@ -0,0 +1,135 @@
+package lifecycle
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"log/slog"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"time"
+
+	"github.com/jmorganca/ollama/api"
+)
+
+func getCLIFullPath(command string) string {
+	cmdPath := ""
+	appExe, err := os.Executable()
+	if err == nil {
+		cmdPath = filepath.Join(filepath.Dir(appExe), command)
+		_, err := os.Stat(cmdPath)
+		if err == nil {
+			return cmdPath
+		}
+	}
+	cmdPath, err = exec.LookPath(command)
+	if err == nil {
+		_, err := os.Stat(cmdPath)
+		if err == nil {
+			return cmdPath
+		}
+	}
+	cmdPath = filepath.Join(".", command)
+	_, err = os.Stat(cmdPath)
+	if err == nil {
+		return cmdPath
+	}
+	return command
+}
+
+func SpawnServer(ctx context.Context, command string) (chan int, error) {
+	done := make(chan int)
+
+	logDir := filepath.Dir(ServerLogFile)
+	_, err := os.Stat(logDir)
+	if errors.Is(err, os.ErrNotExist) {
+		if err := os.MkdirAll(logDir, 0o755); err != nil {
+			return done, fmt.Errorf("create ollama server log dir %s: %v", logDir, err)
+		}
+	}
+
+	cmd := getCmd(ctx, getCLIFullPath(command))
+	// send stdout and stderr to a file
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		return done, fmt.Errorf("failed to spawn server stdout pipe %s", err)
+	}
+	stderr, err := cmd.StderrPipe()
+	if err != nil {
+		return done, fmt.Errorf("failed to spawn server stderr pipe %s", err)
+	}
+	stdin, err := cmd.StdinPipe()
+	if err != nil {
+		return done, fmt.Errorf("failed to spawn server stdin pipe %s", err)
+	}
+
+	// TODO - rotation
+	logFile, err := os.OpenFile(ServerLogFile, os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0755)
+	if err != nil {
+		return done, fmt.Errorf("failed to create server log %w", err)
+	}
+	go func() {
+		defer logFile.Close()
+		io.Copy(logFile, stdout) //nolint:errcheck
+	}()
+	go func() {
+		defer logFile.Close()
+		io.Copy(logFile, stderr) //nolint:errcheck
+	}()
+
+	// run the command and wait for it to finish
+	if err := cmd.Start(); err != nil {
+		return done, fmt.Errorf("failed to start server %w", err)
+	}
+	if cmd.Process != nil {
+		slog.Info(fmt.Sprintf("started ollama server with pid %d", cmd.Process.Pid))
+	}
+	slog.Info(fmt.Sprintf("ollama server logs %s", ServerLogFile))
+
+	go func() {
+		// Keep the server running unless we're shuttind down the app
+		crashCount := 0
+		for {
+			cmd.Wait() //nolint:errcheck
+			stdin.Close()
+			var code int
+			if cmd.ProcessState != nil {
+				code = cmd.ProcessState.ExitCode()
+			}
+
+			select {
+			case <-ctx.Done():
+				slog.Debug(fmt.Sprintf("server shutdown with exit code %d", code))
+				done <- code
+				return
+			default:
+				crashCount++
+				slog.Warn(fmt.Sprintf("server crash %d - exit code %d - respawning", crashCount, code))
+				time.Sleep(500 * time.Millisecond)
+				if err := cmd.Start(); err != nil {
+					slog.Error(fmt.Sprintf("failed to restart server %s", err))
+					// Keep trying, but back off if we keep failing
+					time.Sleep(time.Duration(crashCount) * time.Second)
+				}
+			}
+		}
+	}()
+	return done, nil
+}
+
+func IsServerRunning(ctx context.Context) bool {
+	client, err := api.ClientFromEnvironment()
+	if err != nil {
+		slog.Info("unable to connect to server")
+		return false
+	}
+	err = client.Heartbeat(ctx)
+	if err != nil {
+		slog.Debug(fmt.Sprintf("heartbeat from server: %s", err))
+		slog.Info("unable to connect to server")
+		return false
+	}
+	return true
+}