package main

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

	"github.com/spf13/cobra"

	"git.unkin.net/unkin/tomswall/internal/config"
	"git.unkin.net/unkin/tomswall/internal/nftables"
	"git.unkin.net/unkin/tomswall/internal/shorewall"
	"git.unkin.net/unkin/tomswall/internal/tryapply"
)

var configPath string

func main() {
	root := &cobra.Command{
		Use:   "tomswall",
		Short: "nftables firewall manager — spiritual successor to shorewall",
		Long: `tomswall is a firewall manager that interacts directly with the kernel's
nftables subsystem via the google/nftables library. It supports differential
rule application — no firewall teardown/rebuild needed.

Configuration can be provided in YAML, JSON, or legacy shorewall format.
Use 'tomswall migrate' to convert a shorewall config to YAML.`,
		SilenceUsage: true,
	}

	root.PersistentFlags().StringVarP(&configPath, "config", "c", "/etc/tomswall/tomswall.yaml", "path to configuration file or shorewall directory")

	root.AddCommand(
		applyCmd(),
		tryCmd(),
		confirmCmd(),
		revertCmd(),
		planCmd(),
		validateCmd(),
		statusCmd(),
		purgeCmd(),
		flushCmd(),
		migrateCmd(),
		agentCmd(),
		completionCmd(),
	)

	if err := root.Execute(); err != nil {
		os.Exit(1)
	}
}

func loadConfig() (*config.Config, error) {
	info, err := os.Stat(configPath)
	if err != nil {
		return nil, fmt.Errorf("config path %s: %w", configPath, err)
	}

	var cfg *config.Config
	if info.IsDir() {
		cfg, err = shorewall.Convert(configPath)
		if err != nil {
			return nil, fmt.Errorf("converting shorewall config: %w", err)
		}
	} else {
		cfg, err = config.Load(configPath)
		if err != nil {
			return nil, err
		}
	}

	if err := cfg.Validate(); err != nil {
		return nil, fmt.Errorf("validation: %w", err)
	}
	return cfg, nil
}

func applyCmd() *cobra.Command {
	cmd := &cobra.Command{
		Use:   "apply",
		Short: "Apply configuration to nftables (differential)",
		Long: `Apply computes the difference between the desired configuration and the
current nftables state, then applies only the necessary changes atomically.
The firewall is never torn down — existing connections are preserved.`,
		RunE: func(cmd *cobra.Command, args []string) error {
			cfg, err := loadConfig()
			if err != nil {
				return err
			}

			unlock, err := tryapply.Acquire()
			if err != nil {
				return err
			}
			defer unlock()

			engine, err := nftables.NewEngine(cfg)
			if err != nil {
				return fmt.Errorf("initializing nftables: %w", err)
			}

			changes, err := engine.Plan()
			if err != nil {
				return fmt.Errorf("computing changes: %w", err)
			}

			if changes.Empty() {
				fmt.Println("No changes needed — firewall is up to date.")
				return nil
			}

			fmt.Println(changes.Summary())

			if err := engine.Apply(changes); err != nil {
				return fmt.Errorf("applying changes: %w", err)
			}
			fmt.Println("Changes applied successfully.")
			return nil
		},
	}
	return cmd
}

func planCmd() *cobra.Command {
	return &cobra.Command{
		Use:   "plan",
		Short: "Show planned changes without applying (dry-run)",
		Long: `Plan computes the difference between the desired configuration and the
current nftables state and displays what would change, without modifying
the firewall.`,
		RunE: func(cmd *cobra.Command, args []string) error {
			cfg, err := loadConfig()
			if err != nil {
				return err
			}

			engine, err := nftables.NewEngine(cfg)
			if err != nil {
				return fmt.Errorf("initializing nftables: %w", err)
			}

			changes, err := engine.Plan()
			if err != nil {
				return fmt.Errorf("computing changes: %w", err)
			}

			if changes.Empty() {
				fmt.Println("No changes needed — firewall is up to date.")
				return nil
			}

			fmt.Println("Planned changes:")
			fmt.Println(changes.Summary())
			return nil
		},
	}
}

func validateCmd() *cobra.Command {
	return &cobra.Command{
		Use:   "validate",
		Short: "Validate configuration files",
		Long: `Validate loads and validates the configuration without connecting to
nftables. Checks all config sections for correctness: zones, interfaces,
hosts, policy, rules, SNAT, NAT, netmap, providers, and all other sections.

Accepts YAML, JSON, or a shorewall config directory.`,
		RunE: func(cmd *cobra.Command, args []string) error {
			_, err := loadConfig()
			if err != nil {
				return err
			}
			fmt.Println("Configuration is valid.")
			return nil
		},
	}
}

func statusCmd() *cobra.Command {
	return &cobra.Command{
		Use:   "status",
		Short: "Show current firewall state and pending changes",
		RunE: func(cmd *cobra.Command, args []string) error {
			cfg, err := loadConfig()
			if err != nil {
				return err
			}

			engine, err := nftables.NewEngine(cfg)
			if err != nil {
				return fmt.Errorf("initializing nftables: %w", err)
			}

			changes, err := engine.Plan()
			if err != nil {
				return fmt.Errorf("computing changes: %w", err)
			}

			foreign, err := engine.FindForeignRules()
			if err != nil {
				return fmt.Errorf("scanning foreign rules: %w", err)
			}

			if changes.Empty() && len(foreign) == 0 {
				fmt.Println("Firewall is up to date. No foreign rules detected.")
				return nil
			}

			if !changes.Empty() {
				fmt.Println("Pending changes:")
				fmt.Println(changes.Summary())
			}

			if len(foreign) > 0 {
				fmt.Printf("\nForeign rules detected (%d):\n", len(foreign))
				for _, r := range foreign {
					fmt.Printf("  - %s\n", r)
				}
				fmt.Println("\nUse 'tomswall purge' to remove foreign rules.")
			}

			return nil
		},
	}
}

func purgeCmd() *cobra.Command {
	var dryRun bool
	cmd := &cobra.Command{
		Use:   "purge",
		Short: "Remove rules not managed by tomswall",
		RunE: func(cmd *cobra.Command, args []string) error {
			cfg, err := loadConfig()
			if err != nil {
				return err
			}

			if !dryRun {
				unlock, err := tryapply.Acquire()
				if err != nil {
					return err
				}
				defer unlock()
			}

			engine, err := nftables.NewEngine(cfg)
			if err != nil {
				return fmt.Errorf("initializing nftables: %w", err)
			}

			foreign, err := engine.FindForeignRules()
			if err != nil {
				return fmt.Errorf("scanning: %w", err)
			}

			if len(foreign) == 0 {
				fmt.Println("No foreign rules found.")
				return nil
			}

			fmt.Printf("Found %d foreign rule(s) to remove:\n", len(foreign))
			for _, r := range foreign {
				fmt.Printf("  - %s\n", r)
			}

			if dryRun {
				return nil
			}

			if err := engine.PurgeForeignRules(foreign); err != nil {
				return fmt.Errorf("purging: %w", err)
			}
			fmt.Println("Foreign rules removed.")
			return nil
		},
	}
	cmd.Flags().BoolVar(&dryRun, "dry-run", false, "show foreign rules without removing")
	return cmd
}

func flushCmd() *cobra.Command {
	return &cobra.Command{
		Use:   "flush",
		Short: "Remove all tomswall-managed rules and tables",
		RunE: func(cmd *cobra.Command, args []string) error {
			cfg, err := loadConfig()
			if err != nil {
				return err
			}

			unlock, err := tryapply.Acquire()
			if err != nil {
				return err
			}
			defer unlock()

			engine, err := nftables.NewEngine(cfg)
			if err != nil {
				return fmt.Errorf("initializing nftables: %w", err)
			}

			if err := engine.Flush(); err != nil {
				return fmt.Errorf("flushing: %w", err)
			}
			fmt.Println("All tomswall rules flushed.")
			return nil
		},
	}
}

func migrateCmd() *cobra.Command {
	var outputFormat string
	var outputPath string

	cmd := &cobra.Command{
		Use:   "migrate [shorewall-dir]",
		Short: "Convert a shorewall/shorewall6 config directory to tomswall format",
		Long: `Migrate reads a shorewall or shorewall6 configuration directory and converts
it to tomswall YAML or JSON format. The original config is never modified.
Auto-detects IPv6 mode when shorewall6.conf is present.

Examples:
  tomswall migrate                              # /etc/shorewall -> stdout
  tomswall migrate /etc/shorewall -o config.yaml
  tomswall migrate /etc/shorewall6 -o config6.yaml
  tomswall migrate /etc/shorewall -f json -o config.json`,
		Args: cobra.MaximumNArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			dir := "/etc/shorewall"
			if len(args) > 0 {
				dir = args[0]
			}

			if !shorewall.DirExists(dir) {
				return fmt.Errorf("not a valid shorewall config directory: %s", dir)
			}

			cfg, err := shorewall.Convert(dir)
			if err != nil {
				return fmt.Errorf("converting: %w", err)
			}

			if err := cfg.Validate(); err != nil {
				fmt.Fprintf(os.Stderr, "Warning: converted config has validation issues: %v\n", err)
			}

			var data []byte
			switch strings.ToLower(outputFormat) {
			case "json":
				data, err = json.MarshalIndent(cfg, "", "  ")
			default:
				data, err = cfg.ToYAML()
			}
			if err != nil {
				return fmt.Errorf("serializing: %w", err)
			}

			if outputPath == "" || outputPath == "-" {
				fmt.Print(string(data))
			} else {
				dir := filepath.Dir(outputPath)
				if err := os.MkdirAll(dir, 0755); err != nil {
					return fmt.Errorf("creating output directory: %w", err)
				}
				if err := os.WriteFile(outputPath, data, 0644); err != nil {
					return fmt.Errorf("writing output: %w", err)
				}
				fmt.Fprintf(os.Stderr, "Written to %s\n", outputPath)
			}

			return nil
		},
	}
	cmd.Flags().StringVarP(&outputFormat, "format", "f", "yaml", "output format: yaml or json")
	cmd.Flags().StringVarP(&outputPath, "output", "o", "", "output file path (default: stdout)")
	return cmd
}

func completionCmd() *cobra.Command {
	var install bool

	cmd := &cobra.Command{
		Use:   "completion [bash|zsh]",
		Short: "Generate shell completion scripts",
		Long: `Generate shell completion scripts for bash or zsh.

To load completions in the current session:
  source <(tomswall completion bash)
  source <(tomswall completion zsh)

To install completions permanently:
  tomswall completion bash --install
  tomswall completion zsh --install`,
		ValidArgs: []string{"bash", "zsh"},
		Args:      cobra.ExactArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			root := cmd.Root()
			switch args[0] {
			case "bash":
				if install {
					path := "/etc/bash_completion.d/tomswall"
					f, err := os.Create(path)
					if err != nil {
						home, _ := os.UserHomeDir()
						path = filepath.Join(home, ".local", "share", "bash-completion", "completions", "tomswall")
						if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil {
							return fmt.Errorf("creating completion directory: %w", err)
						}
						f, err = os.Create(path)
						if err != nil {
							return fmt.Errorf("creating completion file: %w", err)
						}
					}
					defer f.Close()
					if err := root.GenBashCompletionV2(f, true); err != nil {
						return err
					}
					fmt.Fprintf(os.Stderr, "Bash completion installed to %s\n", path)
					return nil
				}
				return root.GenBashCompletionV2(os.Stdout, true)
			case "zsh":
				if install {
					path := "/usr/local/share/zsh/site-functions/_tomswall"
					f, err := os.Create(path)
					if err != nil {
						home, _ := os.UserHomeDir()
						path = filepath.Join(home, ".local", "share", "zsh", "site-functions", "_tomswall")
						if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil {
							return fmt.Errorf("creating completion directory: %w", err)
						}
						f, err = os.Create(path)
						if err != nil {
							return fmt.Errorf("creating completion file: %w", err)
						}
					}
					defer f.Close()
					if err := root.GenZshCompletion(f); err != nil {
						return err
					}
					fmt.Fprintf(os.Stderr, "Zsh completion installed to %s\n", path)
					return nil
				}
				return root.GenZshCompletion(os.Stdout)
			default:
				return fmt.Errorf("unsupported shell: %s (use bash or zsh)", args[0])
			}
		},
	}
	cmd.Flags().BoolVar(&install, "install", false, "install completion file to system/user directory")
	return cmd
}