package executor

import (
	"context"
	"fmt"
	"log/slog"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"sync"
	"syscall"
	"time"

	"github.com/thepeterstone/claudomator/internal/storage"
	"github.com/thepeterstone/claudomator/internal/task"
)

// GeminiRunner spawns the `gemini` CLI in non-interactive mode.
type GeminiRunner struct {
	BinaryPath string // defaults to "gemini"
	Logger     *slog.Logger
	LogDir     string // base directory for execution logs
	APIURL     string // base URL of the Claudomator API, passed to subprocesses
}

// ExecLogDir returns the log directory for the given execution ID.
func (r *GeminiRunner) ExecLogDir(execID string) string {
	if r.LogDir == "" {
		return ""
	}
	return filepath.Join(r.LogDir, execID)
}

func (r *GeminiRunner) binaryPath() string {
	if r.BinaryPath != "" {
		return r.BinaryPath
	}
	return "gemini"
}

// Run executes a gemini <instructions> invocation, streaming output to log files.
func (r *GeminiRunner) Run(ctx context.Context, t *task.Task, e *storage.Execution) error {
	if t.Agent.WorkingDir != "" {
		if _, err := os.Stat(t.Agent.WorkingDir); err != nil {
			return fmt.Errorf("working_dir %q: %w", t.Agent.WorkingDir, err)
		}
	}

	logDir := r.ExecLogDir(e.ID)
	if logDir == "" {
		logDir = e.ID
	}
	if err := os.MkdirAll(logDir, 0700); err != nil {
		return fmt.Errorf("creating log dir: %w", err)
	}
	if e.StdoutPath == "" {
		e.StdoutPath = filepath.Join(logDir, "stdout.log")
		e.StderrPath = filepath.Join(logDir, "stderr.log")
		e.ArtifactDir = logDir
	}

	if e.SessionID == "" {
		e.SessionID = e.ID
	}

	questionFile := filepath.Join(logDir, "question.json")
	args := r.buildArgs(t, e, questionFile)

	// Gemini CLI doesn't necessarily have the same rate limiting behavior as Claude,
	// but we'll use a similar execution pattern.
	err := r.execOnce(ctx, args, t.Agent.WorkingDir, e)
	if err != nil {
		return err
	}

	// Check whether the agent left a question before exiting.
	data, readErr := os.ReadFile(questionFile)
	if readErr == nil {
		os.Remove(questionFile) // consumed
		return &BlockedError{QuestionJSON: strings.TrimSpace(string(data)), SessionID: e.SessionID}
	}
	return nil
}

func (r *GeminiRunner) execOnce(ctx context.Context, args []string, workingDir string, e *storage.Execution) error {
	cmd := exec.CommandContext(ctx, r.binaryPath(), args...)
	cmd.Env = append(os.Environ(),
		"CLAUDOMATOR_API_URL="+r.APIURL,
		"CLAUDOMATOR_TASK_ID="+e.TaskID,
		"CLAUDOMATOR_QUESTION_FILE="+filepath.Join(e.ArtifactDir, "question.json"),
	)
	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
	if workingDir != "" {
		cmd.Dir = workingDir
	}

	stdoutFile, err := os.Create(e.StdoutPath)
	if err != nil {
		return fmt.Errorf("creating stdout log: %w", err)
	}
	defer stdoutFile.Close()

	stderrFile, err := os.Create(e.StderrPath)
	if err != nil {
		return fmt.Errorf("creating stderr log: %w", err)
	}
	defer stderrFile.Close()

	stdoutR, stdoutW, err := os.Pipe()
	if err != nil {
		return fmt.Errorf("creating stdout pipe: %w", err)
	}
	cmd.Stdout = stdoutW
	cmd.Stderr = stderrFile

	if err := cmd.Start(); err != nil {
		stdoutW.Close()
		stdoutR.Close()
		return fmt.Errorf("starting gemini: %w", err)
	}
	stdoutW.Close()

	killDone := make(chan struct{})
	go func() {
		select {
		case <-ctx.Done():
			syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL)
		case <-killDone:
		}
	}()

	var costUSD float64
	var streamErr error
	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		// Reusing parseStream as the JSONL format should be compatible
		costUSD, streamErr = parseStream(stdoutR, stdoutFile, r.Logger)
		stdoutR.Close()
	}()

	waitErr := cmd.Wait()
	close(killDone)
	wg.Wait()

	e.CostUSD = costUSD

	if waitErr != nil {
		if exitErr, ok := waitErr.(*exec.ExitError); ok {
			e.ExitCode = exitErr.ExitCode()
		}
		return fmt.Errorf("gemini exited with error: %w", waitErr)
	}

	e.ExitCode = 0
	if streamErr != nil {
		return streamErr
	}
	return nil
}

func (r *GeminiRunner) buildArgs(t *task.Task, e *storage.Execution, questionFile string) []string {
	// Gemini CLI uses a different command structure: gemini "instructions" [flags]
	
	instructions := t.Agent.Instructions
	if !t.Agent.SkipPlanning {
		instructions = withPlanningPreamble(instructions)
	}

	args := []string{
		instructions,
		"--output-format", "stream-json",
	}

	// Note: Gemini CLI flags might differ from Claude CLI.
	// Assuming common flags for now, but these may need adjustment.
	if t.Agent.Model != "" {
		args = append(args, "--model", t.Agent.Model)
	}
	
	// Gemini CLI doesn't use --session-id for the first run in the same way,
	// or it might use it differently. For now we assume compatibility.
	if e.SessionID != "" {
		// If it's a resume, it might use different flags.
		if e.ResumeSessionID != "" {
			// This is a placeholder for Gemini's resume logic
		}
	}

	return args
}