// Package executor provides kubectl exec functionality for running commands in pods.
package executor

import (
	"bufio"
	"context"
	"fmt"
	"io"
	"os/exec"
	"sync"
	"time"
)

// Executor runs commands in Kubernetes pods via kubectl exec.
type Executor struct {
	namespace string
	mu        sync.RWMutex
}

// New creates a new Executor for the given namespace.
func New(namespace string) *Executor {
	return &Executor{
		namespace: namespace,
	}
}

// CommandType represents the type of command being executed.
type CommandType string

const (
	CommandTypeClaude CommandType = "claude"
	CommandTypeShell  CommandType = "shell"
	CommandTypeGit    CommandType = "git"
)

// Command represents a command to execute in a pod.
type Command struct {
	ID        string
	PodName   string
	Type      CommandType
	Args      []string
	StartedAt time.Time
}

// Result represents the result of command execution.
type Result struct {
	ExitCode   int
	DurationMs int64
	Error      error
}

// OutputHandler is called for each line of output from the command.
type OutputHandler func(stream string, line string)

// Exec executes a command in the specified pod.
// It streams output to the provided handler and returns when complete.
func (e *Executor) Exec(ctx context.Context, cmd *Command, handler OutputHandler) Result {
	e.mu.RLock()
	namespace := e.namespace
	e.mu.RUnlock()

	startTime := time.Now()
	var args []string

	switch cmd.Type {
	case CommandTypeClaude:
		// claude "prompt"
		args = []string{
			"exec", "-n", namespace, cmd.PodName, "--",
			"claude", cmd.Args[0], // prompt is first arg
		}
	case CommandTypeShell:
		// bash -c "command"
		args = []string{
			"exec", "-n", namespace, cmd.PodName, "--",
			"bash", "-c", cmd.Args[0], // command is first arg
		}
	case CommandTypeGit:
		// git <args...>
		args = append([]string{
			"exec", "-n", namespace, cmd.PodName, "--",
			"git", "-C", "/workspace",
		}, cmd.Args...)
	default:
		return Result{
			ExitCode: 1,
			Error:    fmt.Errorf("unknown command type: %s", cmd.Type),
		}
	}

	// Create the kubectl command
	kubectl := exec.CommandContext(ctx, "kubectl", args...)

	// Get stdout and stderr pipes
	stdout, err := kubectl.StdoutPipe()
	if err != nil {
		return Result{ExitCode: 1, Error: fmt.Errorf("stdout pipe: %w", err)}
	}
	stderr, err := kubectl.StderrPipe()
	if err != nil {
		return Result{ExitCode: 1, Error: fmt.Errorf("stderr pipe: %w", err)}
	}

	// Start the command
	if err := kubectl.Start(); err != nil {
		return Result{ExitCode: 1, Error: fmt.Errorf("start: %w", err)}
	}

	// Stream output concurrently
	var wg sync.WaitGroup
	wg.Add(2)

	go func() {
		defer wg.Done()
		streamOutput(stdout, "stdout", handler)
	}()

	go func() {
		defer wg.Done()
		streamOutput(stderr, "stderr", handler)
	}()

	// Wait for output to be consumed
	wg.Wait()

	// Wait for command to complete
	err = kubectl.Wait()
	duration := time.Since(startTime)

	result := Result{
		DurationMs: duration.Milliseconds(),
	}

	if err != nil {
		if exitError, ok := err.(*exec.ExitError); ok {
			result.ExitCode = exitError.ExitCode()
		} else {
			result.ExitCode = 1
			result.Error = err
		}
	}

	return result
}

// streamOutput reads from a reader and sends each line to the handler.
func streamOutput(r io.Reader, stream string, handler OutputHandler) {
	scanner := bufio.NewScanner(r)
	// Increase buffer size for long lines
	buf := make([]byte, 0, 64*1024)
	scanner.Buffer(buf, 1024*1024)

	for scanner.Scan() {
		handler(stream, scanner.Text())
	}
}

// CheckConnection verifies kubectl can connect to the cluster.
func (e *Executor) CheckConnection(ctx context.Context) error {
	cmd := exec.CommandContext(ctx, "kubectl", "cluster-info", "--request-timeout=5s")
	return cmd.Run()
}

// PodExists checks if a pod exists and is running.
func (e *Executor) PodExists(ctx context.Context, podName string) (bool, error) {
	e.mu.RLock()
	namespace := e.namespace
	e.mu.RUnlock()

	cmd := exec.CommandContext(ctx, "kubectl",
		"get", "pod", podName,
		"-n", namespace,
		"-o", "jsonpath={.status.phase}",
	)

	output, err := cmd.Output()
	if err != nil {
		// Pod doesn't exist or error
		return false, nil
	}

	return string(output) == "Running", nil
}