package daemon

import (
	"fmt"
	"io"
	"isle/yamlutil"
	"os"
	"path/filepath"
	"strconv"

	"github.com/imdario/mergo"
	"gopkg.in/yaml.v3"
)

func defaultConfigPath(appDirPath string) string {
	return filepath.Join(appDirPath, "etc", "daemon.yml")
}

type ConfigTun struct {
	Device string `yaml:"device"`
}

type ConfigFirewall struct {
	Conntrack ConfigConntrack      `yaml:"conntrack"`
	Outbound  []ConfigFirewallRule `yaml:"outbound"`
	Inbound   []ConfigFirewallRule `yaml:"inbound"`
}

type ConfigConntrack struct {
	TCPTimeout     string `yaml:"tcp_timeout"`
	UDPTimeout     string `yaml:"udp_timeout"`
	DefaultTimeout string `yaml:"default_timeout"`
	MaxConnections int    `yaml:"max_connections"`
}

type ConfigFirewallRule struct {
	Port   string   `yaml:"port,omitempty"`
	Code   string   `yaml:"code,omitempty"`
	Proto  string   `yaml:"proto,omitempty"`
	Host   string   `yaml:"host,omitempty"`
	Group  string   `yaml:"group,omitempty"`
	Groups []string `yaml:"groups,omitempty"`
	CIDR   string   `yaml:"cidr,omitempty"`
	CASha  string   `yaml:"ca_sha,omitempty"`
	CAName string   `yaml:"ca_name,omitempty"`
}

// ConfigStorageAllocation describes the structure of each storage allocation
// within the daemon config file.
type ConfigStorageAllocation struct {
	DataPath  string `yaml:"data_path"`
	MetaPath  string `yaml:"meta_path"`
	Capacity  int    `yaml:"capacity"`
	S3APIPort int    `yaml:"s3_api_port"`
	RPCPort   int    `yaml:"rpc_port"`
	AdminPort int    `yaml:"admin_port"`

	// Zone is a secret option which makes it easier to test garage bugs, but
	// which we don't want users to otherwise know about.
	Zone string `yaml:"zone"`
}

// Config describes the structure of the daemon config file.
type Config struct {
	DNS struct {
		Resolvers []string `yaml:"resolvers"`
	} `yaml:"dns"`
	VPN struct {
		PublicAddr string         `yaml:"public_addr"`
		Firewall   ConfigFirewall `yaml:"firewall"`
		Tun        ConfigTun      `yaml:"tun"`
	} `yaml:"vpn"`
	Storage struct {
		Allocations []ConfigStorageAllocation
	} `yaml:"storage"`
}

func (c *Config) fillDefaults() {

	var firewallGarageInbound []ConfigFirewallRule

	for i := range c.Storage.Allocations {
		if c.Storage.Allocations[i].RPCPort == 0 {
			c.Storage.Allocations[i].RPCPort = 3900 + (i * 10)
		}

		if c.Storage.Allocations[i].S3APIPort == 0 {
			c.Storage.Allocations[i].S3APIPort = 3901 + (i * 10)
		}

		if c.Storage.Allocations[i].AdminPort == 0 {
			c.Storage.Allocations[i].AdminPort = 3902 + (i * 10)
		}

		alloc := c.Storage.Allocations[i]

		firewallGarageInbound = append(
			firewallGarageInbound,
			ConfigFirewallRule{
				Port:  strconv.Itoa(alloc.S3APIPort),
				Proto: "tcp",
				Host:  "any",
			},
			ConfigFirewallRule{
				Port:  strconv.Itoa(alloc.RPCPort),
				Proto: "tcp",
				Host:  "any",
			},
		)
	}

	c.VPN.Firewall.Inbound = append(
		c.VPN.Firewall.Inbound,
		firewallGarageInbound...,
	)
}

// CopyDefaultConfig copies the daemon config file embedded in the AppDir into
// the given io.Writer.
func CopyDefaultConfig(into io.Writer, appDirPath string) error {

	defaultConfigPath := defaultConfigPath(appDirPath)

	f, err := os.Open(defaultConfigPath)
	if err != nil {
		return fmt.Errorf("opening daemon config at %q: %w", defaultConfigPath, err)
	}

	defer f.Close()

	if _, err := io.Copy(into, f); err != nil {
		return fmt.Errorf("copying daemon config from %q: %w", defaultConfigPath, err)
	}

	return nil
}

// LoadConfig loads the daemon config from userConfigPath, merges it with
// the default found in the appDirPath, and returns the result.
//
// If userConfigPath is not given then the default is loaded and returned.
func LoadConfig(
	appDirPath, userConfigPath string,
) (
	Config, error,
) {

	defaultConfigPath := defaultConfigPath(appDirPath)

	var fullDaemon map[string]interface{}

	if err := yamlutil.LoadYamlFile(&fullDaemon, defaultConfigPath); err != nil {
		return Config{}, fmt.Errorf("parsing default daemon config file: %w", err)
	}

	if userConfigPath != "" {

		var daemonConfig map[string]interface{}
		if err := yamlutil.LoadYamlFile(&daemonConfig, userConfigPath); err != nil {
			return Config{}, fmt.Errorf("parsing %q: %w", userConfigPath, err)
		}

		err := mergo.Merge(&fullDaemon, daemonConfig, mergo.WithOverride)
		if err != nil {
			return Config{}, fmt.Errorf("merging contents of file %q: %w", userConfigPath, err)
		}
	}

	fullDaemonB, err := yaml.Marshal(fullDaemon)

	if err != nil {
		return Config{}, fmt.Errorf("yaml marshaling: %w", err)
	}

	var config Config
	if err := yaml.Unmarshal(fullDaemonB, &config); err != nil {
		return Config{}, fmt.Errorf("yaml unmarshaling back into Config struct: %w", err)
	}

	config.fillDefaults()

	return config, nil
}