package cloudflare

import (
	"encoding/base64"
	"encoding/json"
	"errors"
	"io"
	"net/url"
	"os"
	"regexp"
	"strings"

	"gopkg.in/yaml.v3"
)

const (
	credentialsKey  = "credentials.json"
	configKey       = "config.yml"
	credentialsFile = "/etc/cloudflared/credentials.json"
)

var hostnamePattern = regexp.MustCompile(`(?i)^(?:\*\.)?(?:[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?$`)

type Credentials struct {
	AccountTag   string `json:"AccountTag"`
	TunnelSecret string `json:"TunnelSecret"`
	TunnelID     string `json:"TunnelID"`
}

type Route struct {
	Hostname string `yaml:"hostname,omitempty"`
	Service  string `yaml:"service"`
}

type Config struct {
	Tunnel          string  `yaml:"tunnel"`
	CredentialsFile string  `yaml:"credentials-file"`
	Ingress         []Route `yaml:"ingress"`
}

type StoredTunnel struct {
	Credentials Credentials
	Config      Config
}

func NewConfig(tunnelID string) Config {
	return Config{Tunnel: tunnelID, CredentialsFile: credentialsFile, Ingress: []Route{{Service: "http_status:404"}}}
}

func IsLegacyRunTokenState(values map[string]string) bool {
	return len(values) == 1 && strings.TrimSpace(values["token"]) != ""
}

func ReadCredentialsFile(path string) (Credentials, error) {
	contents, err := os.ReadFile(path)
	if err != nil {
		return Credentials{}, errors.New("invalid Cloudflare credentials file")
	}
	if credentials, err := parseCredentials(contents); err == nil {
		return credentials, nil
	}
	credentials, err := credentialsFromSecret(contents)
	if err != nil {
		return Credentials{}, errors.New("invalid Cloudflare credentials file")
	}
	return credentials, nil
}

func credentialsFromSecret(contents []byte) (Credentials, error) {
	var secret struct {
		APIVersion string            `yaml:"apiVersion"`
		Kind       string            `yaml:"kind"`
		StringData map[string]string `yaml:"stringData"`
		Data       map[string]string `yaml:"data"`
	}
	decoder := yaml.NewDecoder(strings.NewReader(string(contents)))
	if err := decoder.Decode(&secret); err != nil || decoder.Decode(&struct{}{}) != io.EOF || secret.APIVersion != "v1" || secret.Kind != "Secret" {
		return Credentials{}, errors.New("invalid Secret")
	}
	plaintext, inStringData := secret.StringData[credentialsKey]
	encoded, inData := secret.Data[credentialsKey]
	if inStringData == inData {
		return Credentials{}, errors.New("missing Secret credentials")
	}
	if inStringData {
		return parseCredentials([]byte(plaintext))
	}
	decoded, err := base64.StdEncoding.DecodeString(encoded)
	if err != nil {
		return Credentials{}, errors.New("invalid Secret credentials")
	}
	return parseCredentials(decoded)
}

func NewRoute(hostname, service string) (Route, error) {
	hostname = strings.ToLower(strings.TrimSuffix(strings.TrimSpace(hostname), "."))
	if len(hostname) > 253 || !hostnamePattern.MatchString(hostname) {
		return Route{}, errors.New("hostname must be a valid public DNS hostname")
	}
	parsed, err := url.ParseRequestURI(service)
	if err != nil || (parsed.Scheme != "http" && parsed.Scheme != "https") || parsed.Host == "" || parsed.User != nil || parsed.Fragment != "" {
		return Route{}, errors.New("service must be an absolute http or https URL")
	}
	return Route{Hostname: hostname, Service: service}, nil
}

func ParseStoredTunnel(values map[string]string) (StoredTunnel, bool, error) {
	credentialsJSON, hasCredentials := values[credentialsKey]
	configYAML, hasConfig := values[configKey]
	if !hasCredentials && !hasConfig {
		if len(values) == 0 {
			return StoredTunnel{}, false, nil
		}
		return StoredTunnel{}, false, errors.New("Cloudflare tunnel operational state is ambiguous; expected credentials.json and config.yml")
	}
	if !hasCredentials || !hasConfig || len(values) != 2 {
		return StoredTunnel{}, false, errors.New("Cloudflare tunnel operational state is ambiguous; expected only credentials.json and config.yml")
	}
	credentials, err := parseCredentials([]byte(credentialsJSON))
	if err != nil {
		return StoredTunnel{}, false, err
	}
	var config Config
	yamlDecoder := yaml.NewDecoder(strings.NewReader(configYAML))
	yamlDecoder.KnownFields(true)
	if err := yamlDecoder.Decode(&config); err != nil || yamlDecoder.Decode(&struct{}{}) != io.EOF || !validConfig(config) || config.Tunnel != credentials.TunnelID {
		return StoredTunnel{}, false, errors.New("Cloudflare tunnel config is invalid")
	}
	return StoredTunnel{Credentials: credentials, Config: config}, true, nil
}

func parseCredentials(contents []byte) (Credentials, error) {
	var credentials Credentials
	decoder := json.NewDecoder(strings.NewReader(string(contents)))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&credentials); err != nil || decoder.Decode(&struct{}{}) != io.EOF || credentials.AccountTag == "" || credentials.TunnelSecret == "" || credentials.TunnelID == "" {
		return Credentials{}, errors.New("Cloudflare tunnel credentials are invalid")
	}
	return credentials, nil
}

func (s StoredTunnel) Values() (map[string]string, error) {
	credentials, err := json.Marshal(s.Credentials)
	if err != nil {
		return nil, errors.New("encode Cloudflare tunnel credentials")
	}
	config, err := yaml.Marshal(s.Config)
	if err != nil {
		return nil, errors.New("encode Cloudflare tunnel config")
	}
	return map[string]string{credentialsKey: string(credentials), configKey: string(config)}, nil
}

func (c *Config) AddRoute(route Route) (bool, error) {
	if !validConfig(*c) {
		return false, errors.New("Cloudflare tunnel config is invalid")
	}
	for _, existing := range c.Ingress[:len(c.Ingress)-1] {
		if existing.Hostname == route.Hostname {
			if existing.Service == route.Service {
				return false, nil
			}
			return false, errors.New("hostname already has a different Cloudflare tunnel route")
		}
	}
	terminal := c.Ingress[len(c.Ingress)-1]
	c.Ingress = append(c.Ingress[:len(c.Ingress)-1], route, terminal)
	return true, nil
}

func (c *Config) RemoveRoute(route Route) (bool, error) {
	if !validConfig(*c) {
		return false, errors.New("Cloudflare tunnel config is invalid")
	}
	for index, existing := range c.Ingress[:len(c.Ingress)-1] {
		if existing.Hostname != route.Hostname {
			continue
		}
		if existing.Service != route.Service {
			return false, errors.New("hostname does not match the requested Cloudflare tunnel service")
		}
		c.Ingress = append(c.Ingress[:index], c.Ingress[index+1:]...)
		return true, nil
	}
	return false, nil
}

func validConfig(config Config) bool {
	if config.Tunnel == "" || config.CredentialsFile != credentialsFile || len(config.Ingress) == 0 {
		return false
	}
	last := len(config.Ingress) - 1
	if config.Ingress[last].Hostname != "" || config.Ingress[last].Service != "http_status:404" {
		return false
	}
	seen := map[string]bool{}
	for _, route := range config.Ingress[:last] {
		normalized, err := NewRoute(route.Hostname, route.Service)
		if err != nil || normalized != route || seen[route.Hostname] {
			return false
		}
		seen[route.Hostname] = true
	}
	return true
}