package executor

import (
	"bufio"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log/slog"
	"os"
	"os/exec"
	"path/filepath"

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

// ClaudeRunner spawns the `claude` CLI in non-interactive mode.
type ClaudeRunner struct {
	BinaryPath string // defaults to "claude"
	Logger     *slog.Logger
	LogDir     string // base directory for execution logs
}

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

// Run executes a claude -p invocation, streaming output to log files.
func (r *ClaudeRunner) Run(ctx context.Context, t *task.Task, e *storage.Execution) error {
	args := r.buildArgs(t)

	cmd := exec.CommandContext(ctx, r.binaryPath(), args...)
	if t.Claude.WorkingDir != "" {
		cmd.Dir = t.Claude.WorkingDir
	}

	// Setup log directory for this execution.
	logDir := filepath.Join(r.LogDir, e.ID)
	if err := os.MkdirAll(logDir, 0700); err != nil {
		return fmt.Errorf("creating log dir: %w", err)
	}

	stdoutPath := filepath.Join(logDir, "stdout.log")
	stderrPath := filepath.Join(logDir, "stderr.log")
	e.StdoutPath = stdoutPath
	e.StderrPath = stderrPath
	e.ArtifactDir = logDir

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

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

	stdoutPipe, err := cmd.StdoutPipe()
	if err != nil {
		return fmt.Errorf("creating stdout pipe: %w", err)
	}
	stderrPipe, err := cmd.StderrPipe()
	if err != nil {
		return fmt.Errorf("creating stderr pipe: %w", err)
	}

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

	// Stream output to log files and parse cost info.
	var costUSD float64
	go func() {
		costUSD = streamAndParseCost(stdoutPipe, stdoutFile, r.Logger)
	}()
	go io.Copy(stderrFile, stderrPipe)

	if err := cmd.Wait(); err != nil {
		if exitErr, ok := err.(*exec.ExitError); ok {
			e.ExitCode = exitErr.ExitCode()
		}
		e.CostUSD = costUSD
		return fmt.Errorf("claude exited with error: %w", err)
	}

	e.ExitCode = 0
	e.CostUSD = costUSD
	return nil
}

func (r *ClaudeRunner) buildArgs(t *task.Task) []string {
	args := []string{
		"-p", t.Claude.Instructions,
		"--output-format", "stream-json",
	}

	if t.Claude.Model != "" {
		args = append(args, "--model", t.Claude.Model)
	}
	if t.Claude.MaxBudgetUSD > 0 {
		args = append(args, "--max-budget-usd", fmt.Sprintf("%.2f", t.Claude.MaxBudgetUSD))
	}
	if t.Claude.PermissionMode != "" {
		args = append(args, "--permission-mode", t.Claude.PermissionMode)
	}
	if t.Claude.SystemPromptAppend != "" {
		args = append(args, "--append-system-prompt", t.Claude.SystemPromptAppend)
	}
	for _, tool := range t.Claude.AllowedTools {
		args = append(args, "--allowedTools", tool)
	}
	for _, tool := range t.Claude.DisallowedTools {
		args = append(args, "--disallowedTools", tool)
	}
	for _, f := range t.Claude.ContextFiles {
		args = append(args, "--add-dir", f)
	}
	args = append(args, t.Claude.AdditionalArgs...)

	return args
}

// streamAndParseCost reads streaming JSON from claude and writes to the log file,
// extracting cost data from the stream.
func streamAndParseCost(r io.Reader, w io.Writer, logger *slog.Logger) float64 {
	tee := io.TeeReader(r, w)
	scanner := bufio.NewScanner(tee)
	scanner.Buffer(make([]byte, 1024*1024), 1024*1024) // 1MB buffer for large lines

	var totalCost float64
	for scanner.Scan() {
		line := scanner.Bytes()
		var msg map[string]interface{}
		if err := json.Unmarshal(line, &msg); err != nil {
			continue
		}
		// Extract cost from result messages.
		if costData, ok := msg["cost_usd"]; ok {
			if cost, ok := costData.(float64); ok {
				totalCost = cost
			}
		}
	}
	return totalCost
}