package agents

import (
	"bytes"
	"context"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"time"

	"g.fc.run/ai/byre/internal/mcp"
)

func (m *Manager) renderDiagramTool() mcp.Tool {
	return mcp.Tool{
		Name: "render_diagram",
		Description: "See a diagram as byre's app draws it in the transcript: pass the body of a ```diagram block and get back a PNG of the result, drawn by the app's own renderer in light mode. " +
			"A source the app can't draw comes back as the reason instead.",
		InputSchema: json.RawMessage(`{
			"type": "object",
			"properties": {
				"source": {"type": "string", "description": "The block's body, without the fence lines."}
			},
			"required": ["source"]
		}`),
		Rich: func(ctx context.Context, raw json.RawMessage) mcp.Result {
			args := struct {
				Source string `json:"source"`
			}{}
			err := json.Unmarshal(raw, &args)
			if err != nil {
				return mcp.TextResult(fmt.Sprintf("malformed render_diagram call: %v", err), true)
			}
			png, err := renderDiagram(ctx, args.Source)
			if err != nil {
				return mcp.TextResult(err.Error(), true)
			}
			return mcp.Result{Content: []mcp.Content{{Type: "image", Data: base64.StdEncoding.EncodeToString(png), MimeType: "image/png"}}}
		},
	}
}

func renderDiagram(ctx context.Context, source string) ([]byte, error) {
	exe, err := os.Executable()
	if err != nil {
		return nil, err
	}
	app := filepath.Join(filepath.Dir(exe), "..", "MacOS", "Byre")
	ctx, cancel := context.WithTimeout(ctx, 30*time.Second)
	defer cancel()
	cmd := exec.CommandContext(ctx, app, "render-diagram")
	cmd.Stdin = strings.NewReader(source)
	stderr := bytes.Buffer{}
	cmd.Stderr = &stderr
	out, err := cmd.Output()
	if err != nil {
		return nil, fmt.Errorf("render diagram: %w: %s", err, strings.TrimSpace(stderr.String()))
	}
	return out, nil
}