package tools

import (
	"bufio"
	"context"
	"encoding/json"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"sort"
	"strings"
	"time"

	"github.com/kujtimiihoxha/termai/internal/config"
)

type grepTool struct{}

const (
	GrepToolName = "grep"
)

type GrepParams struct {
	Pattern string `json:"pattern"`
	Path    string `json:"path"`
	Include string `json:"include"`
}

type grepMatch struct {
	path    string
	modTime time.Time
}

func (g *grepTool) Info() ToolInfo {
	return ToolInfo{
		Name:        GrepToolName,
		Description: grepDescription(),
		Parameters: map[string]any{
			"pattern": map[string]any{
				"type":        "string",
				"description": "The regex pattern to search for in file contents",
			},
			"path": map[string]any{
				"type":        "string",
				"description": "The directory to search in. Defaults to the current working directory.",
			},
			"include": map[string]any{
				"type":        "string",
				"description": "File pattern to include in the search (e.g. \"*.js\", \"*.{ts,tsx}\")",
			},
		},
		Required: []string{"pattern"},
	}
}

// Run implements Tool.
func (g *grepTool) Run(ctx context.Context, call ToolCall) (ToolResponse, error) {
	var params GrepParams
	if err := json.Unmarshal([]byte(call.Input), &params); err != nil {
		return NewTextErrorResponse(fmt.Sprintf("error parsing parameters: %s", err)), nil
	}

	if params.Pattern == "" {
		return NewTextErrorResponse("pattern is required"), nil
	}

	// If path is empty, use current working directory
	searchPath := params.Path
	if searchPath == "" {
		searchPath = config.WorkingDirectory()
	}

	matches, truncated, err := searchFiles(params.Pattern, searchPath, params.Include, 100)
	if err != nil {
		return NewTextErrorResponse(fmt.Sprintf("error searching files: %s", err)), nil
	}

	// Format the output for the assistant
	var output string
	if len(matches) == 0 {
		output = "No files found"
	} else {
		output = fmt.Sprintf("Found %d file%s\n%s",
			len(matches),
			pluralize(len(matches)),
			strings.Join(matches, "\n"))

		if truncated {
			output += "\n\n(Results are truncated. Consider using a more specific path or pattern.)"
		}
	}

	return NewTextResponse(output), nil
}

func pluralize(count int) string {
	if count == 1 {
		return ""
	}
	return "s"
}

func searchFiles(pattern, rootPath, include string, limit int) ([]string, bool, error) {
	// First try using ripgrep if available for better performance
	matches, err := searchWithRipgrep(pattern, rootPath, include)
	if err != nil {
		// Fall back to manual regex search if ripgrep is not available
		matches, err = searchFilesWithRegex(pattern, rootPath, include)
		if err != nil {
			return nil, false, err
		}
	}

	// Sort files by modification time (newest first)
	sort.Slice(matches, func(i, j int) bool {
		return matches[i].modTime.After(matches[j].modTime)
	})

	// Check if we need to truncate the results
	truncated := len(matches) > limit
	if truncated {
		matches = matches[:limit]
	}

	// Extract just the paths
	results := make([]string, len(matches))
	for i, m := range matches {
		results[i] = m.path
	}

	return results, truncated, nil
}

func searchWithRipgrep(pattern, path, include string) ([]grepMatch, error) {
	_, err := exec.LookPath("rg")
	if err != nil {
		return nil, fmt.Errorf("ripgrep not found: %w", err)
	}

	args := []string{"-l", pattern}
	if include != "" {
		args = append(args, "--glob", include)
	}
	args = append(args, path)

	cmd := exec.Command("rg", args...)
	output, err := cmd.Output()
	if err != nil {
		if exitErr, ok := err.(*exec.ExitError); ok && exitErr.ExitCode() == 1 {
			// Exit code 1 means no matches, which isn't an error for our purposes
			return []grepMatch{}, nil
		}
		return nil, err
	}

	lines := strings.Split(strings.TrimSpace(string(output)), "\n")
	matches := make([]grepMatch, 0, len(lines))

	for _, line := range lines {
		if line == "" {
			continue
		}

		fileInfo, err := os.Stat(line)
		if err != nil {
			continue // Skip files we can't access
		}

		matches = append(matches, grepMatch{
			path:    line,
			modTime: fileInfo.ModTime(),
		})
	}

	return matches, nil
}

func searchFilesWithRegex(pattern, rootPath, include string) ([]grepMatch, error) {
	matches := []grepMatch{}

	regex, err := regexp.Compile(pattern)
	if err != nil {
		return nil, fmt.Errorf("invalid regex pattern: %w", err)
	}

	var includePattern *regexp.Regexp
	if include != "" {
		regexPattern := globToRegex(include)
		includePattern, err = regexp.Compile(regexPattern)
		if err != nil {
			return nil, fmt.Errorf("invalid include pattern: %w", err)
		}
	}

	err = filepath.Walk(rootPath, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return nil // Skip errors
		}

		if info.IsDir() {
			return nil // Skip directories
		}

		// Skip hidden files
		if skipHidden(path) {
			return nil
		}

		// Check include pattern if provided
		if includePattern != nil && !includePattern.MatchString(path) {
			return nil
		}

		// Check file contents for the pattern
		match, err := fileContainsPattern(path, regex)
		if err != nil {
			return nil // Skip files we can't read
		}

		if match {
			matches = append(matches, grepMatch{
				path:    path,
				modTime: info.ModTime(),
			})

			// Check if we've hit the limit (collect double for sorting)
			if len(matches) >= 200 {
				return filepath.SkipAll
			}
		}

		return nil
	})
	if err != nil {
		return nil, err
	}

	return matches, nil
}

func fileContainsPattern(filePath string, pattern *regexp.Regexp) (bool, error) {
	file, err := os.Open(filePath)
	if err != nil {
		return false, err
	}
	defer file.Close()

	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		if pattern.MatchString(scanner.Text()) {
			return true, nil
		}
	}

	return false, scanner.Err()
}

func globToRegex(glob string) string {
	regexPattern := strings.ReplaceAll(glob, ".", "\\.")
	regexPattern = strings.ReplaceAll(regexPattern, "*", ".*")
	regexPattern = strings.ReplaceAll(regexPattern, "?", ".")

	re := regexp.MustCompile(`\{([^}]+)\}`)
	regexPattern = re.ReplaceAllStringFunc(regexPattern, func(match string) string {
		inner := match[1 : len(match)-1]
		return "(" + strings.ReplaceAll(inner, ",", "|") + ")"
	})

	return regexPattern
}

func grepDescription() string {
	return `Fast content search tool that finds files containing specific text or patterns, returning matching file paths sorted by modification time (newest first).

WHEN TO USE THIS TOOL:
- Use when you need to find files containing specific text or patterns
- Great for searching code bases for function names, variable declarations, or error messages
- Useful for finding all files that use a particular API or pattern

HOW TO USE:
- Provide a regex pattern to search for within file contents
- Optionally specify a starting directory (defaults to current working directory)
- Optionally provide an include pattern to filter which files to search
- Results are sorted with most recently modified files first

REGEX PATTERN SYNTAX:
- Supports standard regular expression syntax
- 'function' searches for the literal text "function"
- 'log\..*Error' finds text starting with "log." and ending with "Error"
- 'import\s+.*\s+from' finds import statements in JavaScript/TypeScript

COMMON INCLUDE PATTERN EXAMPLES:
- '*.js' - Only search JavaScript files
- '*.{ts,tsx}' - Only search TypeScript files
- '*.go' - Only search Go files

LIMITATIONS:
- Results are limited to 100 files (newest first)
- Performance depends on the number of files being searched
- Very large binary files may be skipped
- Hidden files (starting with '.') are skipped

TIPS:
- For faster, more targeted searches, first use Glob to find relevant files, then use Grep
- When doing iterative exploration that may require multiple rounds of searching, consider using the Agent tool instead
- Always check if results are truncated and refine your search pattern if needed`
}

func NewGrepTool() BaseTool {
	return &grepTool{}
}