package main

import (
	"flag"
	"fmt"
	"log"
	"os"
	"strings"
	"time"

	"github.com/hexops/gotextdiff"
	"github.com/hexops/gotextdiff/myers"
	"github.com/hexops/gotextdiff/span"
	"gopkg.in/yaml.v3"
)

type Config struct {
	Listen      []string `yaml:"listen"`
	Checkpoints string   `yaml:"checkpoints"`
	Roots       string   `yaml:"roots"`
	Logs        []Log    `yaml:"logs"`
}

type Log struct {
	ShortName        string    `yaml:"shortname"`
	Inception        string    `yaml:"inception"`
	Period           int       `yaml:"period"`
	PoolSize         int       `yaml:"poolsize"`
	SubmissionPrefix string    `yaml:"submissionprefix"`
	MonitoringPrefix string    `yaml:"monitoringprefix"`
	CCadbRoots       string    `yaml:"ccadbroots"`
	ExtraRoots       string    `yaml:"extraroots"`
	Secret           string    `yaml:"secret"`
	Cache            string    `yaml:"cache"`
	LocalDirectory   string    `yaml:"localdirectory"`
	Listen           string    `yaml:"listen"`
	NotAfterStart    time.Time `yaml:"notafterstart"`
	NotAfterLimit    time.Time `yaml:"notafterlimit"`
	// Computed fields
	LogID           string
	PublicKeyPEM    string
	PublicKeyDERB64 string
	PublicKeyBase64 string
}

func main() {
	configFile := flag.String("c", "./tesseract-staging.yaml", "Path to the YAML configuration file")
	wantDiff := flag.Bool("diff", false, "Show unified diff of changes")
	allowWrite := flag.Bool("write", false, "Allow writing files (required for actual file modifications)")
	noColor := flag.Bool("no-color", false, "Disable colored diff output")
	flag.Parse()

	args := flag.Args()
	if len(args) == 0 {
		showHelp()
		return
	}

	switch args[0] {
	case "gen-html":
		generateHTML(*configFile, *wantDiff, *allowWrite, !*noColor)
	case "gen-env":
		generateEnv(*configFile, *wantDiff, *allowWrite, !*noColor)
	case "gen-key":
		generateKeys(*configFile, *wantDiff, *allowWrite, !*noColor)
	case "gen-nginx":
		generateNginx(*configFile, *wantDiff, *allowWrite, !*noColor)
	case "gen-roots":
		generateRoots(args[1:], *wantDiff, *allowWrite, !*noColor)
	default:
		fmt.Fprintf(os.Stderr, "Unknown command: %s\n", args[0])
		showHelp()
		os.Exit(1)
	}
}

func loadConfig(yamlFile string) Config {
	data, err := os.ReadFile(yamlFile)
	if err != nil {
		log.Fatalf("Failed to read YAML file: %v", err)
	}

	var config Config
	err = yaml.Unmarshal(data, &config)
	if err != nil {
		log.Fatalf("Failed to parse YAML: %v", err)
	}

	// Set default listen port if not configured
	if len(config.Listen) == 0 {
		config.Listen = []string{":8080"}
	}

	// Set defaults for log entries
	for i := range config.Logs {
		if config.Logs[i].PoolSize == 0 {
			config.Logs[i].PoolSize = 750
		}
		if config.Logs[i].Period == 0 {
			config.Logs[i].Period = 200
		}
	}

	return config
}

// ANSI color codes
const (
	colorReset  = "\033[0m"
	colorRed    = "\033[31m"
	colorGreen  = "\033[32m"
	colorYellow = "\033[33m"
	colorCyan   = "\033[36m"
)

// colorizeUnifiedDiff adds ANSI color codes to unified diff output
func colorizeUnifiedDiff(diff string) string {
	lines := strings.Split(diff, "\n")
	var colorizedLines []string

	for _, line := range lines {
		switch {
		case strings.HasPrefix(line, "---"):
			// File deletion header in cyan
			colorizedLines = append(colorizedLines, colorCyan+line+colorReset)
		case strings.HasPrefix(line, "+++"):
			// File addition header in cyan
			colorizedLines = append(colorizedLines, colorCyan+line+colorReset)
		case strings.HasPrefix(line, "@@"):
			// Hunk header in yellow
			colorizedLines = append(colorizedLines, colorYellow+line+colorReset)
		case strings.HasPrefix(line, "-"):
			// Deleted lines in red
			colorizedLines = append(colorizedLines, colorRed+line+colorReset)
		case strings.HasPrefix(line, "+"):
			// Added lines in green
			colorizedLines = append(colorizedLines, colorGreen+line+colorReset)
		default:
			// Context lines unchanged
			colorizedLines = append(colorizedLines, line)
		}
	}

	return strings.Join(colorizedLines, "\n")
}

func writeFileWithStatus(filename string, content []byte, wantDiff bool, allowWrite bool, useColor bool) error {
	existingContent, err := os.ReadFile(filename)
	isNew := os.IsNotExist(err)
	isUnchanged := false

	if isNew {
		if allowWrite {
			fmt.Printf("Creating %s\n", filename)
		} else {
			fmt.Printf("Would create %s\n", filename)
		}
	} else if err != nil {
		return fmt.Errorf("failed to read existing file %s: %v", filename, err)
	} else if string(existingContent) == string(content) {
		fmt.Printf("Unchanged %s\n", filename)
		isUnchanged = true
	} else {
		if allowWrite {
			fmt.Printf("Updating %s\n", filename)
		} else {
			fmt.Printf("Would update %s\n", filename)
		}
	}

	if wantDiff && !isUnchanged {
		if isNew {
			// For new files, show the entire content as added
			edits := myers.ComputeEdits(span.URIFromPath(filename), "", string(content))
			diff := fmt.Sprint(gotextdiff.ToUnified("/dev/null", filename, "", edits))
			if useColor {
				fmt.Print(colorizeUnifiedDiff(diff))
			} else {
				fmt.Print(diff)
			}
		} else {
			// For existing files, show the diff
			edits := myers.ComputeEdits(span.URIFromPath(filename), string(existingContent), string(content))
			diff := fmt.Sprint(gotextdiff.ToUnified(filename, filename+".new", string(existingContent), edits))
			if useColor {
				fmt.Print(colorizeUnifiedDiff(diff))
			} else {
				fmt.Print(diff)
			}
		}
	}

	if isUnchanged || !allowWrite {
		return nil
	}

	err = os.WriteFile(filename, content, 0644)
	if err != nil {
		return fmt.Errorf("failed to write file %s: %v", filename, err)
	}
	return nil
}

func showHelp() {
	fmt.Printf("Usage: %s [options] <command>\n\n", os.Args[0])
	fmt.Printf("Note: Flags must come before the command name.\n\n")
	fmt.Printf("Options:\n")
	fmt.Printf("  -c <file>    Path to YAML configuration file (default: ./tesseract-staging.yaml)\n")
	fmt.Printf("  --diff       Show unified diff of changes without writing files\n")
	fmt.Printf("  --write      Allow writing files (required for actual file modifications)\n")
	fmt.Printf("  --no-color   Disable colored diff output\n\n")
	fmt.Printf("Examples:\n")
	fmt.Printf("  %s --diff gen-html            # Show colored diffs without writing\n", os.Args[0])
	fmt.Printf("  %s --diff --no-color gen-html # Show plain diffs without writing\n", os.Args[0])
	fmt.Printf("  %s --write gen-html           # Write files\n", os.Args[0])
	fmt.Printf("  %s --diff --write gen-html    # Show colored diffs and write files\n\n", os.Args[0])
	fmt.Printf("Commands:\n")
	fmt.Printf("  gen-html     Generate index.html and log.v3.json files in each log's localdirectory.\n")
	fmt.Printf("               Creates HTML pages with log information and CT log metadata JSON.\n")
	fmt.Printf("               Computes LOG_ID and public keys from private keys.\n\n")
	fmt.Printf("  gen-env      Generate .env files and combined roots.pem in each log's localdirectory.\n")
	fmt.Printf("               Creates TESSERACT_ARGS environment variable with command line flags.\n")
	fmt.Printf("               Combines global roots and log-specific extraroots into roots.pem.\n\n")
	fmt.Printf("  gen-key      Generate prime256v1 private keys for each log (only if they don't exist).\n")
	fmt.Printf("               Creates EC private key files at the path specified in log.secret.\n\n")
	fmt.Printf("  gen-nginx    Generate nginx configuration files for each log's monitoring endpoint.\n")
	fmt.Printf("               Creates nginx-<hostname>.conf files in each log's localdirectory.\n\n")
	fmt.Printf("  gen-roots    Download root certificates from a Certificate Transparency log.\n")
	fmt.Printf("               Options: --source <url> (default: https://rennet2027h2.log.ct.ipng.ch/)\n")
	fmt.Printf("                        --output <file> (default: roots.pem)\n\n")
}