package tools

import (
	"bufio"
	"context"
	"fmt"
	"os"
	"strings"

	llm "gitea.stevedudenhoeffer.com/steve/go-llm/v2"
)

// ReadFileParams defines parameters for the read file tool.
type ReadFileParams struct {
	Path  string `json:"path" description:"File path to read"`
	Start *int   `json:"start,omitempty" description:"Starting line number (1-based, inclusive)"`
	End   *int   `json:"end,omitempty" description:"Ending line number (1-based, inclusive)"`
}

// ReadFile creates a file reading tool.
//
// Example:
//
//	tools := llm.NewToolBox(tools.ReadFile())
func ReadFile() llm.Tool {
	return llm.Define[ReadFileParams]("read_file", "Read the contents of a file",
		func(ctx context.Context, p ReadFileParams) (string, error) {
			f, err := os.Open(p.Path)
			if err != nil {
				return "", fmt.Errorf("opening file: %w", err)
			}
			defer f.Close()

			// If no line range specified, read the whole file (limited to 1MB)
			if p.Start == nil && p.End == nil {
				info, err := f.Stat()
				if err != nil {
					return "", fmt.Errorf("stat file: %w", err)
				}
				if info.Size() > 1<<20 {
					return "", fmt.Errorf("file too large (%d bytes), use start/end to read a range", info.Size())
				}
				data, err := os.ReadFile(p.Path)
				if err != nil {
					return "", fmt.Errorf("reading file: %w", err)
				}
				return string(data), nil
			}

			// Read specific line range
			start := 1
			end := -1
			if p.Start != nil {
				start = *p.Start
			}
			if p.End != nil {
				end = *p.End
			}

			var lines []string
			scanner := bufio.NewScanner(f)
			lineNum := 0
			for scanner.Scan() {
				lineNum++
				if lineNum < start {
					continue
				}
				if end > 0 && lineNum > end {
					break
				}
				lines = append(lines, fmt.Sprintf("%d: %s", lineNum, scanner.Text()))
			}

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

			return strings.Join(lines, "\n"), nil
		},
	)
}