coding-agent/tools.go

package main

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"
)

type Tool struct {
	Type     string       `json:"type"`
	Function ToolFunction `json:"function"`
}

type ToolFunction struct {
	Name        string         `json:"name"`
	Description string         `json:"description"`
	Parameters  map[string]any `json:"parameters"`
}

func toolDefinitions() []Tool {
	return []Tool{
		{
			Type: "function",
			Function: ToolFunction{
				Name:        "read_file",
				Description: "Read a UTF-8 text file relative to the project root. Returns the file contents.",
				Parameters: map[string]any{
					"type": "object",
					"properties": map[string]any{
						"path": map[string]any{
							"type":        "string",
							"description": "Relative path from the project root.",
						},
					},
					"required": []string{"path"},
				},
			},
		},
		{
			Type: "function",
			Function: ToolFunction{
				Name:        "create_file",
				Description: "Create a new file with the given content. Fails if the file already exists. Parent directories are created as needed.",
				Parameters: map[string]any{
					"type": "object",
					"properties": map[string]any{
						"path":    map[string]any{"type": "string", "description": "Relative path from the project root."},
						"content": map[string]any{"type": "string", "description": "Full file contents to write."},
					},
					"required": []string{"path", "content"},
				},
			},
		},
		{
			Type: "function",
			Function: ToolFunction{
				Name:        "edit_file",
				Description: "Overwrite an existing file with new content. Fails if the file does not exist.",
				Parameters: map[string]any{
					"type": "object",
					"properties": map[string]any{
						"path":    map[string]any{"type": "string", "description": "Relative path from the project root."},
						"content": map[string]any{"type": "string", "description": "Full replacement contents."},
					},
					"required": []string{"path", "content"},
				},
			},
		},
		{
			Type: "function",
			Function: ToolFunction{
				Name:        "delete_file",
				Description: "Delete a file. Fails if the path is a directory or does not exist.",
				Parameters: map[string]any{
					"type": "object",
					"properties": map[string]any{
						"path": map[string]any{"type": "string", "description": "Relative path from the project root."},
					},
					"required": []string{"path"},
				},
			},
		},
		{
			Type: "function",
			Function: ToolFunction{
				Name:        "list_directory",
				Description: "List the entries of a directory, relative to the project root. Use \".\" for the root.",
				Parameters: map[string]any{
					"type": "object",
					"properties": map[string]any{
						"path": map[string]any{"type": "string", "description": "Relative directory path. Use \".\" for the project root."},
					},
					"required": []string{"path"},
				},
			},
		},
	}
}

// runTool executes a tool call and returns a string payload for the model.
// Errors are returned as strings too so the model can react, not fatal.
func runTool(root, name, argsJSON string) string {
	var a struct {
		Path    string `json:"path"`
		Content string `json:"content"`
	}
	if argsJSON != "" {
		if err := json.Unmarshal([]byte(argsJSON), &a); err != nil {
			return fmt.Sprintf("error: invalid arguments: %v", err)
		}
	}

	switch name {
	case "read_file":
		return doRead(root, a.Path)
	case "create_file":
		return doCreate(root, a.Path, a.Content)
	case "edit_file":
		return doEdit(root, a.Path, a.Content)
	case "delete_file":
		return doDelete(root, a.Path)
	case "list_directory":
		return doList(root, a.Path)
	default:
		return fmt.Sprintf("error: unknown tool %q", name)
	}
}

func doRead(root, p string) string {
	abs, err := resolveSafe(root, p)
	if err != nil {
		return "error: " + err.Error()
	}
	b, err := os.ReadFile(abs)
	if err != nil {
		return "error: " + err.Error()
	}
	return string(b)
}

func doCreate(root, p, content string) string {
	abs, err := resolveSafe(root, p)
	if err != nil {
		return "error: " + err.Error()
	}
	if _, err := os.Stat(abs); err == nil {
		return fmt.Sprintf("error: file already exists: %s", p)
	}
	if err := os.MkdirAll(filepath.Dir(abs), 0o755); err != nil {
		return "error: " + err.Error()
	}
	if err := os.WriteFile(abs, []byte(content), 0o644); err != nil {
		return "error: " + err.Error()
	}
	return fmt.Sprintf("created %s (%d bytes)", p, len(content))
}

func doEdit(root, p, content string) string {
	abs, err := resolveSafe(root, p)
	if err != nil {
		return "error: " + err.Error()
	}
	info, err := os.Stat(abs)
	if err != nil {
		return "error: " + err.Error()
	}
	if info.IsDir() {
		return fmt.Sprintf("error: path is a directory: %s", p)
	}
	if err := os.WriteFile(abs, []byte(content), 0o644); err != nil {
		return "error: " + err.Error()
	}
	return fmt.Sprintf("updated %s (%d bytes)", p, len(content))
}

func doDelete(root, p string) string {
	abs, err := resolveSafe(root, p)
	if err != nil {
		return "error: " + err.Error()
	}
	if abs == root {
		return "error: refusing to delete project root"
	}
	info, err := os.Stat(abs)
	if err != nil {
		return "error: " + err.Error()
	}
	if info.IsDir() {
		return fmt.Sprintf("error: path is a directory: %s", p)
	}
	if err := os.Remove(abs); err != nil {
		return "error: " + err.Error()
	}
	return fmt.Sprintf("deleted %s", p)
}

func doList(root, p string) string {
	if p == "" {
		p = "."
	}
	abs, err := resolveSafe(root, p)
	if err != nil {
		return "error: " + err.Error()
	}
	entries, err := os.ReadDir(abs)
	if err != nil {
		return "error: " + err.Error()
	}
	lines := make([]string, 0, len(entries))
	for _, e := range entries {
		name := e.Name()
		if e.IsDir() {
			name += "/"
		}
		lines = append(lines, name)
	}
	sort.Strings(lines)
	if len(lines) == 0 {
		return "(empty)"
	}
	return strings.Join(lines, "\n")
}