package deploy

import (
	"bytes"
	"context"
	"fmt"
	"os/exec"
	"time"

	"git.t-juice.club/torjus/homelab-deploy/internal/messages"
)

// Executor handles the execution of nixos-rebuild commands.
type Executor struct {
	flakeURL string
	hostname string
	timeout  time.Duration
}

// NewExecutor creates a new deployment executor.
func NewExecutor(flakeURL, hostname string, timeout time.Duration) *Executor {
	return &Executor{
		flakeURL: flakeURL,
		hostname: hostname,
		timeout:  timeout,
	}
}

// Result contains the result of a deployment execution.
type Result struct {
	Success  bool
	ExitCode int
	Stdout   string
	Stderr   string
	Error    error
}

// ExecuteOptions contains optional settings for Execute.
type ExecuteOptions struct {
	// HeartbeatInterval is how often to call the heartbeat callback.
	// If zero, no heartbeat is sent.
	HeartbeatInterval time.Duration
	// HeartbeatCallback is called periodically with elapsed time while the command runs.
	HeartbeatCallback func(elapsed time.Duration)
}

// ValidateRevision checks if a revision exists in the remote repository.
// It uses git ls-remote to verify the ref exists.
func (e *Executor) ValidateRevision(ctx context.Context, revision string) error {
	// Extract the base URL for git ls-remote
	// flakeURL is like git+https://git.example.com/user/repo.git
	// We need to strip the git+ prefix for git ls-remote
	gitURL := e.flakeURL
	if len(gitURL) > 4 && gitURL[:4] == "git+" {
		gitURL = gitURL[4:]
	}

	ctx, cancel := context.WithTimeout(ctx, 30*time.Second)
	defer cancel()

	cmd := exec.CommandContext(ctx, "git", "ls-remote", "--exit-code", gitURL, revision)
	var stderr bytes.Buffer
	cmd.Stderr = &stderr

	if err := cmd.Run(); err != nil {
		if ctx.Err() == context.DeadlineExceeded {
			return fmt.Errorf("timeout validating revision")
		}
		return fmt.Errorf("revision %q not found: %w", revision, err)
	}

	return nil
}

// Execute runs nixos-rebuild with the specified action and revision.
func (e *Executor) Execute(ctx context.Context, action messages.Action, revision string) *Result {
	return e.ExecuteWithOptions(ctx, action, revision, nil)
}

// ExecuteWithOptions runs nixos-rebuild with the specified action, revision, and options.
func (e *Executor) ExecuteWithOptions(ctx context.Context, action messages.Action, revision string, opts *ExecuteOptions) *Result {
	ctx, cancel := context.WithTimeout(ctx, e.timeout)
	defer cancel()

	// Build the flake reference: <flake-url>?ref=<revision>#<hostname>
	flakeRef := fmt.Sprintf("%s?ref=%s#%s", e.flakeURL, revision, e.hostname)

	cmd := exec.CommandContext(ctx, "nixos-rebuild", string(action), "--flake", flakeRef)

	var stdout, stderr bytes.Buffer
	cmd.Stdout = &stdout
	cmd.Stderr = &stderr

	// Start the command
	startTime := time.Now()
	if err := cmd.Start(); err != nil {
		return &Result{
			Success:  false,
			ExitCode: -1,
			Error:    fmt.Errorf("failed to start command: %w", err),
		}
	}

	// Set up heartbeat if configured
	var heartbeatDone chan struct{}
	if opts != nil && opts.HeartbeatInterval > 0 && opts.HeartbeatCallback != nil {
		heartbeatDone = make(chan struct{})
		go func() {
			ticker := time.NewTicker(opts.HeartbeatInterval)
			defer ticker.Stop()
			for {
				select {
				case <-heartbeatDone:
					return
				case <-ticker.C:
					opts.HeartbeatCallback(time.Since(startTime))
				}
			}
		}()
	}

	// Wait for command to complete
	err := cmd.Wait()

	// Stop heartbeat goroutine
	if heartbeatDone != nil {
		close(heartbeatDone)
	}

	result := &Result{
		Stdout: stdout.String(),
		Stderr: stderr.String(),
	}

	if err != nil {
		result.Success = false
		result.Error = err

		if ctx.Err() == context.DeadlineExceeded {
			result.Error = fmt.Errorf("deployment timed out after %v", e.timeout)
		}

		if exitErr, ok := err.(*exec.ExitError); ok {
			result.ExitCode = exitErr.ExitCode()
		} else {
			result.ExitCode = -1
		}
	} else {
		result.Success = true
		result.ExitCode = 0
	}

	return result
}

// BuildCommand returns the command that would be executed (for logging/debugging).
func (e *Executor) BuildCommand(action messages.Action, revision string) string {
	flakeRef := fmt.Sprintf("%s?ref=%s#%s", e.flakeURL, revision, e.hostname)
	return fmt.Sprintf("nixos-rebuild %s --flake %s", action, flakeRef)
}