package file

import (
	"context"
	"fmt"
	"os"
	"path/filepath"

	"github.com/enmanuel/agents/internal/config"
	"github.com/enmanuel/agents/tools"
)

// maxWriteSize is the maximum content size for write_file (1 MB).
const maxWriteSize = 1 * 1024 * 1024

// NewWriteFile creates a write_file tool that writes content to a local file.
// Deny-by-default: if AllowedPaths is empty, all writes are rejected.
// Rejects if ReadOnly is true. Creates parent directories if needed.
func NewWriteFile(cfg config.FileOpsCfg) tools.Tool {
	return tools.Tool{
		Def: tools.Def{
			Name:        "write_file",
			Description: "Write content to a local file. Creates the file if it does not exist. Creates parent directories if needed. Overwrites existing content.",
			Parameters: []tools.Param{
				{Name: "path", Type: "string", Description: "Absolute path to the file to write", Required: true},
				{Name: "content", Type: "string", Description: "Content to write to the file", Required: true},
			},
		},
		Exec: func(ctx context.Context, args map[string]any) tools.Result {
			path := tools.GetString(args, "path")
			if path == "" {
				return tools.Result{Err: fmt.Errorf("write_file: path is required")}
			}

			content := tools.GetString(args, "content")
			if content == "" {
				return tools.Result{Err: fmt.Errorf("write_file: content is required")}
			}

			if len(content) > maxWriteSize {
				return tools.Result{Err: fmt.Errorf("write_file: content exceeds maximum size of 1 MB")}
			}

			absPath, err := filepath.Abs(path)
			if err != nil {
				return tools.Result{Err: fmt.Errorf("write_file: %w", err)}
			}

			if err := validateWritePath(absPath, cfg.AllowedPaths, cfg.ReadOnly); err != nil {
				return tools.Result{Err: err}
			}

			// Create parent directories if they don't exist.
			dir := filepath.Dir(absPath)
			if err := os.MkdirAll(dir, 0755); err != nil {
				return tools.Result{Err: fmt.Errorf("write_file: cannot create directories: %w", err)}
			}

			data := []byte(content)
			if err := os.WriteFile(absPath, data, 0644); err != nil {
				return tools.Result{Err: fmt.Errorf("write_file: %w", err)}
			}

			return tools.Result{Output: fmt.Sprintf("wrote %d bytes to %s", len(data), absPath)}
		},
	}
}
