// Package claudecode provides a CodeAgent implementation for Anthropic's Claude Code CLI.
package claudecode

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

	"github.com/orchard9/rdev/internal/domain"
	"github.com/orchard9/rdev/internal/port"
)

// Adapter implements port.CodeAgent using Anthropic's Claude Code CLI.
type Adapter struct {
	namespace string
	mu        sync.RWMutex

	// Track active sessions for cancellation
	activeSessions map[string]context.CancelFunc
	sessionsMu     sync.Mutex
}

// NewAdapter creates a new Claude Code adapter.
func NewAdapter(namespace string) *Adapter {
	return &Adapter{
		namespace:      namespace,
		activeSessions: make(map[string]context.CancelFunc),
	}
}

// Ensure Adapter implements port.CodeAgent at compile time.
var _ port.CodeAgent = (*Adapter)(nil)

// Name returns a human-readable name for this agent.
func (a *Adapter) Name() string {
	return "Claude Code"
}

// Provider returns the agent provider identifier.
func (a *Adapter) Provider() domain.AgentProvider {
	return domain.AgentProviderClaudeCode
}

// Execute runs a Claude Code command and streams events to the handler.
func (a *Adapter) Execute(ctx context.Context, req *domain.AgentRequest, handler domain.AgentEventHandler) (*domain.AgentResult, error) {
	if req.Prompt == "" {
		return nil, fmt.Errorf("prompt is required")
	}

	a.mu.RLock()
	namespace := a.namespace
	a.mu.RUnlock()

	// Create cancellable context
	execCtx, cancel := context.WithCancel(ctx)
	defer cancel()

	// Track session for potential cancellation
	sessionID := generateSessionID()
	a.sessionsMu.Lock()
	a.activeSessions[sessionID] = cancel
	a.sessionsMu.Unlock()

	defer func() {
		a.sessionsMu.Lock()
		delete(a.activeSessions, sessionID)
		a.sessionsMu.Unlock()
	}()

	// Get pod name from project (passed via metadata or lookup)
	var podName string
	if req.Metadata != nil {
		podName = req.Metadata["pod_name"]
	}
	if podName == "" {
		return &domain.AgentResult{
			SessionID: sessionID,
			ExitCode:  1,
			Error:     fmt.Errorf("pod_name is required in request metadata"),
		}, nil
	}

	// Build kubectl exec command for Claude Code
	args := a.buildCommandArgs(namespace, podName, req)

	// Apply timeout if specified
	if req.Timeout > 0 {
		var timeoutCancel context.CancelFunc
		execCtx, timeoutCancel = context.WithTimeout(execCtx, req.Timeout)
		defer timeoutCancel()
	}

	startTime := time.Now()
	kubectl := exec.CommandContext(execCtx, "kubectl", args...)

	// Get stdout pipe for stream-json output
	stdout, err := kubectl.StdoutPipe()
	if err != nil {
		return &domain.AgentResult{
			SessionID: sessionID,
			ExitCode:  1,
			Error:     fmt.Errorf("stdout pipe: %w", err),
		}, nil
	}

	// Get stderr for error messages
	stderr, err := kubectl.StderrPipe()
	if err != nil {
		return &domain.AgentResult{
			SessionID: sessionID,
			ExitCode:  1,
			Error:     fmt.Errorf("stderr pipe: %w", err),
		}, nil
	}

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

	// Stream and parse output
	var wg sync.WaitGroup
	var finalOutput strings.Builder
	var stderrOutput strings.Builder
	var parseErr error
	var resultMsg *StreamMessage

	wg.Add(2)

	// Parse stream-json from stdout
	go func() {
		defer wg.Done()
		resultMsg, parseErr = a.parseStreamOutput(stdout, handler, &finalOutput)
	}()

	// Stream stderr as error events and capture for error message
	go func() {
		defer wg.Done()
		a.streamStderrCapture(stderr, handler, &stderrOutput)
	}()

	wg.Wait()

	// Wait for command completion
	cmdErr := kubectl.Wait()
	duration := time.Since(startTime)

	result := &domain.AgentResult{
		SessionID:   sessionID,
		DurationMs:  duration.Milliseconds(),
		FinalOutput: finalOutput.String(),
	}

	// Determine exit code and error
	if cmdErr != nil {
		if exitErr, ok := cmdErr.(*exec.ExitError); ok {
			result.ExitCode = exitErr.ExitCode()
		} else {
			result.ExitCode = 1
			result.Error = cmdErr
		}
		// Include stderr and troubleshooting help in error
		result.Error = a.buildErrorWithHelp(result.Error, stderrOutput.String(), namespace, podName)
	} else if parseErr != nil {
		result.ExitCode = 1
		result.Error = a.buildErrorWithHelp(parseErr, stderrOutput.String(), namespace, podName)
	} else if resultMsg != nil && !resultMsg.IsSuccess() {
		result.ExitCode = 1
		if resultMsg.Error != "" {
			result.Error = a.buildErrorWithHelp(fmt.Errorf("%s", resultMsg.Error), stderrOutput.String(), namespace, podName)
		} else {
			result.Error = a.buildErrorWithHelp(nil, stderrOutput.String(), namespace, podName)
		}
	}

	// Update session ID from result if available
	if resultMsg != nil && resultMsg.SessionID != "" {
		result.SessionID = resultMsg.SessionID
	}

	return result, nil
}

// defaultAllowedTools is the list of tools to allow when running Claude Code
// in automated mode. Using --allowedTools instead of --dangerously-skip-permissions
// because the latter is blocked when running as root (which claudebox pods do).
var defaultAllowedTools = []string{
	"Bash", "Edit", "Write", "Read", "Glob", "Grep", "Task", "WebFetch", "WebSearch",
}

// buildCommandArgs constructs the kubectl exec arguments for Claude Code.
// IMPORTANT: The prompt MUST come immediately after "claude" (before other flags)
// because Claude Code's CLI parser expects the positional prompt argument early.
func (a *Adapter) buildCommandArgs(namespace, podName string, req *domain.AgentRequest) []string {
	// Start with kubectl exec and the prompt right after "claude"
	// This is required because Claude Code's CLI doesn't accept the prompt at the end
	args := []string{
		"exec", "-n", namespace, podName, "--",
		"claude",
		req.Prompt,  // Prompt MUST come first after "claude"
		"-p",        // Print mode (non-interactive)
		"--verbose", // Required for stream-json output
		"--output-format", "stream-json",
	}

	// Add session continuation if resuming
	if req.SessionID != "" {
		args = append(args, "--resume", req.SessionID)
	}

	// Add allowed tools - use request's tools if specified, otherwise use defaults.
	// This replaces --dangerously-skip-permissions which is blocked when running as root.
	allowedTools := req.AllowedTools
	if len(allowedTools) == 0 {
		allowedTools = defaultAllowedTools
	}
	for _, tool := range allowedTools {
		args = append(args, "--allowedTools", tool)
	}

	// Add working directory if specified
	if req.WorkingDir != "" && req.WorkingDir != "/workspace" {
		args = append(args, "--add-dir", req.WorkingDir)
	}

	return args
}

// parseStreamOutput reads and parses NDJSON stream-json output.
func (a *Adapter) parseStreamOutput(r io.Reader, handler domain.AgentEventHandler, output *strings.Builder) (*StreamMessage, error) {
	scanner := bufio.NewScanner(r)
	// Increase buffer for long lines
	buf := make([]byte, 0, 64*1024)
	scanner.Buffer(buf, 1024*1024)

	var resultMsg *StreamMessage

	for scanner.Scan() {
		line := scanner.Bytes()
		if len(line) == 0 {
			continue
		}

		msg, err := ParseStreamMessage(line)
		if err != nil {
			// Non-JSON line, treat as plain output
			event := domain.AgentEvent{
				Type:      domain.AgentEventOutput,
				Timestamp: time.Now(),
				Content:   string(line),
				Stream:    "stdout",
			}
			handler(event)
			output.WriteString(string(line))
			output.WriteString("\n")
			continue
		}

		// Convert to agent event and dispatch
		event := msg.ToAgentEvent()
		handler(event)

		// Collect output text
		if msg.Type == StreamMessageMessage && msg.Role == "assistant" {
			text := extractTextContent(msg.Content)
			if text != "" {
				output.WriteString(text)
			}
		}

		// Track result message
		if msg.IsTerminal() {
			resultMsg = msg
		}
	}

	if err := scanner.Err(); err != nil {
		return resultMsg, fmt.Errorf("scanner error: %w", err)
	}

	return resultMsg, nil
}

// streamStderrCapture reads stderr, emits error events, and captures output.
func (a *Adapter) streamStderrCapture(r io.Reader, handler domain.AgentEventHandler, capture *strings.Builder) {
	scanner := bufio.NewScanner(r)
	buf := make([]byte, 0, 64*1024)
	scanner.Buffer(buf, 1024*1024)

	for scanner.Scan() {
		line := scanner.Text()
		if line == "" {
			continue
		}

		handler(domain.AgentEvent{
			Type:      domain.AgentEventError,
			Timestamp: time.Now(),
			Content:   line,
			Stream:    "stderr",
		})

		// Capture stderr for error message (limit to 4KB)
		if capture.Len() < 4096 {
			if capture.Len() > 0 {
				capture.WriteString("\n")
			}
			capture.WriteString(line)
		}
	}
}

// buildErrorWithHelp creates an error message with stderr output and troubleshooting help.
func (a *Adapter) buildErrorWithHelp(err error, stderr, namespace, podName string) error {
	var msg strings.Builder

	if err != nil {
		msg.WriteString(err.Error())
	} else {
		msg.WriteString("claude command failed")
	}

	// Include stderr if available
	if stderr != "" {
		msg.WriteString("\n\nstderr:\n")
		msg.WriteString(stderr)
	}

	// Add troubleshooting help
	msg.WriteString("\n\n---\nTroubleshooting:\n")
	msg.WriteString("If Claude is not authenticated, run:\n")
	fmt.Fprintf(&msg, "  kubectl exec -it -n %s %s -- claude login\n", namespace, podName)
	msg.WriteString("\nTo test Claude manually:\n")
	fmt.Fprintf(&msg, "  kubectl exec -it -n %s %s -- claude -p \"hello\"\n", namespace, podName)

	return fmt.Errorf("%s", msg.String())
}

// Cancel attempts to cancel a running session.
func (a *Adapter) Cancel(ctx context.Context, sessionID string) error {
	a.sessionsMu.Lock()
	defer a.sessionsMu.Unlock()

	cancel, exists := a.activeSessions[sessionID]
	if !exists {
		return nil // Session not found is not an error
	}

	cancel()
	return nil
}

// Capabilities returns what this agent supports.
func (a *Adapter) Capabilities() domain.AgentCapabilities {
	return domain.AgentCapabilities{
		Provider:                    domain.AgentProviderClaudeCode,
		SupportsSessionContinuation: true,
		SupportsModelSelection:      false, // Claude Code only uses Claude
		SupportsToolControl:         true,
		SupportedModels:             []string{"claude-sonnet-4-20250514", "claude-opus-4-20250514"},
		DefaultModel:                "claude-sonnet-4-20250514",
		MaxPromptLength:             0, // Unlimited
		SupportsStreaming:           true,
	}
}

// DefaultAvailabilityTimeout is the maximum time to wait when checking agent availability.
// This timeout prevents blocking the caller when kubectl or the cluster is slow or unresponsive.
const DefaultAvailabilityTimeout = 5 * time.Second

// Available checks if kubectl is available and can connect to the cluster.
func (a *Adapter) Available(ctx context.Context) bool {
	ctx, cancel := context.WithTimeout(ctx, DefaultAvailabilityTimeout)
	defer cancel()

	cmd := exec.CommandContext(ctx, "kubectl", "cluster-info", "--request-timeout=5s")
	return cmd.Run() == nil
}

// sessionCounter is used to ensure unique session IDs.
var sessionCounter atomic.Uint64

// generateSessionID creates a unique session identifier.
func generateSessionID() string {
	count := sessionCounter.Add(1)
	return fmt.Sprintf("claude-%d-%d", time.Now().UnixNano(), count)
}