package main

import (
	"errors"
	"fmt"
	"isle/daemon/daecommon"
	"slices"
	"strings"

	"golang.org/x/exp/maps"
)

const vpnFirewallConfigChangeStagerName = "vpn-firewall-config"

// vpnFirewallGetConfigWithStaged returns the network config along with any
// staged firewall configuration changes, if there are any.
func vpnFirewallGetConfig(ctx subCmdCtx) (daecommon.NetworkConfig, error) {
	config, err := ctx.getDaemonRPC().GetConfig(ctx)
	if err != nil {
		return daecommon.NetworkConfig{}, err
	}

	var firewallConfig daecommon.ConfigFirewall
	if ok, err := ctx.opts.changeStager.get(
		&firewallConfig, vpnFirewallConfigChangeStagerName,
	); err != nil {
		return daecommon.NetworkConfig{}, fmt.Errorf(
			"getting staged VPN firewall config: %w", err,
		)
	} else if ok {
		config.VPN.Firewall = firewallConfig
	}

	return config, nil
}

func vpnFirewallRuleSetToFn(
	str string,
) (
	func(*daecommon.ConfigFirewall) *[]daecommon.ConfigFirewallRule,
	error,
) {
	switch strings.ToLower(str) {
	case "outbound":
		return func(c *daecommon.ConfigFirewall) *[]daecommon.ConfigFirewallRule {
			return &c.Outbound
		}, nil
	case "inbound":
		return func(c *daecommon.ConfigFirewall) *[]daecommon.ConfigFirewallRule {
			return &c.Inbound
		}, nil
	default:
		return nil, fmt.Errorf("must be 'inbound' or 'outbound'")
	}
}

var subCmdVPNFirewallAdd = subCmd{
	name:  "add",
	descr: "Add a new firewall rule to the staged configuration",
	do: func(ctx subCmdCtx) error {
		to := ctx.flags.String(
			"to",
			"",
			"Which set of rules to add to, either 'inbound' or 'outbound'",
		)

		var rule daecommon.ConfigFirewallRule
		ctx.flags.StringVar(
			&rule.Port, "port", "any", "Port number or range to allow",
		)

		ctx.flags.StringVar(
			&rule.Proto,
			"proto",
			"any",
			"Protocol to allow. Can be 'tcp', 'udp', 'icmp', or 'any'",
		)

		ctx.flags.StringVar(
			&rule.Host,
			"host",
			"",
			"Name of host to allow. Defaults to 'any' if --groups is not given",
		)

		ctx.flags.StringSliceVar(
			&rule.Groups,
			"groups",
			nil,
			"One or more comma-separated group names to allow",
		)

		ctx, err := ctx.withParsedFlags()
		if err != nil {
			return fmt.Errorf("parsing flags: %w", err)
		}

		if *to == "" {
			return errors.New("--to is required")
		}

		ruleSetFn, err := vpnFirewallRuleSetToFn(*to)
		if err != nil {
			return fmt.Errorf("invalid --to value %q: %w", *to, err)
		}

		if rule.Host != "" && len(rule.Groups) > 0 {
			return fmt.Errorf("--host and --groups are mutually exclusive")
		} else if rule.Host == "" && len(rule.Groups) == 0 {
			rule.Host = "any"
		}

		config, err := vpnFirewallGetConfig(ctx)
		if err != nil {
			return fmt.Errorf("getting network config: %w", err)
		}

		ruleSet := ruleSetFn(&config.VPN.Firewall)
		*ruleSet = append(*ruleSet, rule)

		if err := config.Validate(); err != nil {
			return err
		}

		if err := ctx.opts.changeStager.set(
			config.VPN.Firewall, vpnFirewallConfigChangeStagerName,
		); err != nil {
			return fmt.Errorf("staging changes: %w", err)
		}

		return nil
	},
}

var subCmdVPNFirewallRemove = subCmd{
	name:  "remove",
	descr: "Remove one or more firewall rules from the staged configuration",
	do: func(ctx subCmdCtx) error {
		from := ctx.flags.String(
			"from",
			"",
			"Which set of rules to remove from, either 'inbound' or 'outbound'",
		)

		indexes := ctx.flags.IntSlice(
			"indexes",
			nil,
			"Comma-separated indexes of rules to remove, as returned by 'vpn firewall show --staged'",
		)

		ctx, err := ctx.withParsedFlags()
		if err != nil {
			return fmt.Errorf("parsing flags: %w", err)
		}

		if *from == "" || len(*indexes) == 0 {
			return errors.New("--from and --indexes are required")
		}

		ruleSetFn, err := vpnFirewallRuleSetToFn(*from)
		if err != nil {
			return fmt.Errorf("invalid --from value %q: %w", *from, err)
		}

		indexSet := map[int]struct{}{}
		for _, index := range *indexes {
			if index < 0 {
				return fmt.Errorf("invalid index %d", index)
			}
			indexSet[index] = struct{}{}
		}

		config, err := vpnFirewallGetConfig(ctx)
		if err != nil {
			return fmt.Errorf("getting network config: %w", err)
		}

		var (
			ruleSet         = ruleSetFn(&config.VPN.Firewall)
			filteredRuleSet = make(
				[]daecommon.ConfigFirewallRule, 0, len(*ruleSet),
			)
		)

		for i, rule := range *ruleSet {
			if _, remove := indexSet[i]; remove {
				delete(indexSet, i)
				continue
			}
			filteredRuleSet = append(filteredRuleSet, rule)
		}

		if len(indexSet) > 0 {
			invalidIndexes := maps.Keys(indexSet)
			slices.Sort(invalidIndexes)
			return fmt.Errorf("invalid index(es): %v", invalidIndexes)
		}

		*ruleSet = filteredRuleSet

		if err := config.Validate(); err != nil {
			return err
		}

		if err := ctx.opts.changeStager.set(
			config.VPN.Firewall, vpnFirewallConfigChangeStagerName,
		); err != nil {
			return fmt.Errorf("staging changes: %w", err)
		}

		return nil
	},
}

type firewallRuleView struct {
	Index                        int `yaml:"index"`
	daecommon.ConfigFirewallRule `yaml:",inline"`
}

func newFirewallRuleViews(
	rules []daecommon.ConfigFirewallRule,
) []firewallRuleView {
	views := make([]firewallRuleView, len(rules))
	for i := range rules {
		views[i] = firewallRuleView{
			Index:              i,
			ConfigFirewallRule: rules[i],
		}
	}
	return views
}

type firewallView struct {
	Outbound []firewallRuleView `yaml:"outbound"`
	Inbound  []firewallRuleView `yaml:"inbound"`
}

func newFirewallView(firewallConfig daecommon.ConfigFirewall) firewallView {
	return firewallView{
		Outbound: newFirewallRuleViews(firewallConfig.Outbound),
		Inbound:  newFirewallRuleViews(firewallConfig.Inbound),
	}
}

var subCmdVPNFirewallShow = subCmd{
	name:  "show",
	descr: "Shows the currently configured firewall rules",
	do: doWithOutput(func(ctx subCmdCtx) (any, error) {
		staged := ctx.flags.Bool(
			"staged",
			false,
			"Return the firewall configuration with staged changes included",
		)

		ctx, err := ctx.withParsedFlags()
		if err != nil {
			return nil, fmt.Errorf("parsing flags: %w", err)
		}

		var (
			firewallConfig daecommon.ConfigFirewall
			foundStaged    bool
		)
		if *staged {
			var err error
			if foundStaged, err = ctx.opts.changeStager.get(
				&firewallConfig, vpnFirewallConfigChangeStagerName,
			); err != nil {
				return nil, fmt.Errorf("checking for staged changes: %w", err)
			}
		}

		if !foundStaged {
			config, err := ctx.getDaemonRPC().GetConfig(ctx)
			if err != nil {
				return nil, fmt.Errorf("getting network config: %w", err)
			}

			firewallConfig = config.VPN.Firewall
		}

		return newFirewallView(firewallConfig), nil
	}),
}

var subCmdVPNFirewall = subCmd{
	name:  "firewall",
	descr: "Sub-commands related to this host's VPN firewall",
	do: func(ctx subCmdCtx) error {
		return ctx.doSubCmd(
			subCmdVPNFirewallAdd,
			subCmdVPNFirewallRemove,
			subCmdVPNFirewallShow,
		)
	},
}