package config

import (
	"errors"
	"fmt"
	"net"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"time"

	"gopkg.in/yaml.v3"
)

type Duration struct {
	time.Duration
}

func (d *Duration) UnmarshalYAML(node *yaml.Node) error {
	if node == nil || node.Value == "" {
		d.Duration = 0
		return nil
	}

	parsed, err := time.ParseDuration(node.Value)
	if err != nil {
		return fmt.Errorf("invalid duration %q: %w", node.Value, err)
	}
	d.Duration = parsed
	return nil
}

func (d Duration) MarshalYAML() (any, error) {
	return d.String(), nil
}

type Config struct {
	Server   ServerConfig             `yaml:"server"`
	Storage  StorageConfig            `yaml:"storage"`
	OPNsense OPNsenseConfig           `yaml:"opnsense"`
	Profiles map[string]ProfileConfig `yaml:"profiles"`
	Sources  []SourceConfig           `yaml:"sources"`
}

type ServerConfig struct {
	ListenAddress   string   `yaml:"listen_address"`
	ReadTimeout     Duration `yaml:"read_timeout"`
	WriteTimeout    Duration `yaml:"write_timeout"`
	ShutdownTimeout Duration `yaml:"shutdown_timeout"`
}

type StorageConfig struct {
	Path string `yaml:"path"`
}

type OPNsenseConfig struct {
	Enabled            bool           `yaml:"enabled"`
	BaseURL            string         `yaml:"base_url"`
	APIKey             string         `yaml:"api_key"`
	APISecret          string         `yaml:"api_secret"`
	APIKeyFile         string         `yaml:"api_key_file"`
	APISecretFile      string         `yaml:"api_secret_file"`
	Timeout            Duration       `yaml:"timeout"`
	InsecureSkipVerify bool           `yaml:"insecure_skip_verify"`
	EnsureAlias        bool           `yaml:"ensure_alias"`
	Alias              AliasConfig    `yaml:"alias"`
	APIPaths           APIPathsConfig `yaml:"api_paths"`
}

type AliasConfig struct {
	Name        string `yaml:"name"`
	Type        string `yaml:"type"`
	Description string `yaml:"description"`
}

type APIPathsConfig struct {
	AliasGetUUID    string `yaml:"alias_get_uuid"`
	AliasAddItem    string `yaml:"alias_add_item"`
	AliasSetItem    string `yaml:"alias_set_item"`
	AliasReconfig   string `yaml:"alias_reconfigure"`
	AliasUtilList   string `yaml:"alias_util_list"`
	AliasUtilAdd    string `yaml:"alias_util_add"`
	AliasUtilDelete string `yaml:"alias_util_delete"`
}

type SourceConfig struct {
	Name            string   `yaml:"name"`
	Path            string   `yaml:"path"`
	Profile         string   `yaml:"profile"`
	InitialPosition string   `yaml:"initial_position"`
	PollInterval    Duration `yaml:"poll_interval"`
	BatchSize       int      `yaml:"batch_size"`
}

type KnownAgentRule struct {
	Name              string   `yaml:"name"`
	Decision          string   `yaml:"decision"`
	UserAgentPrefixes []string `yaml:"user_agent_prefixes"`
	CIDRs             []string `yaml:"cidrs"`

	normalizedPrefixes []string
	networks           []*net.IPNet
}

type ProfileConfig struct {
	AutoBlock              bool             `yaml:"auto_block"`
	MinStatus              int              `yaml:"min_status"`
	MaxStatus              int              `yaml:"max_status"`
	BlockUnexpectedPosts   bool             `yaml:"block_unexpected_posts"`
	BlockPHPPaths          bool             `yaml:"block_php_paths"`
	AllowedPostPaths       []string         `yaml:"allowed_post_paths"`
	SuspiciousPathPrefixes []string         `yaml:"suspicious_path_prefixes"`
	ExcludedCIDRs          []string         `yaml:"excluded_cidrs"`
	KnownAgents            []KnownAgentRule `yaml:"known_agents"`

	normalizedAllowedPostPaths map[string]struct{}
	normalizedSuspiciousPaths  []string
	excludedNetworks           []*net.IPNet
}

func Load(path string) (*Config, error) {
	payload, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("read config: %w", err)
	}

	var cfg Config
	if err := yaml.Unmarshal(payload, &cfg); err != nil {
		return nil, fmt.Errorf("decode config: %w", err)
	}

	if err := cfg.applyDefaults(); err != nil {
		return nil, err
	}

	if err := cfg.validate(path); err != nil {
		return nil, err
	}

	return &cfg, nil
}

func (c *Config) applyDefaults() error {
	if c.Server.ListenAddress == "" {
		c.Server.ListenAddress = "127.0.0.1:9080"
	}
	if c.Server.ReadTimeout.Duration == 0 {
		c.Server.ReadTimeout.Duration = 5 * time.Second
	}
	if c.Server.WriteTimeout.Duration == 0 {
		c.Server.WriteTimeout.Duration = 10 * time.Second
	}
	if c.Server.ShutdownTimeout.Duration == 0 {
		c.Server.ShutdownTimeout.Duration = 15 * time.Second
	}
	if c.Storage.Path == "" {
		c.Storage.Path = "./data/caddy-opnsense-blocker.db"
	}

	if c.OPNsense.Timeout.Duration == 0 {
		c.OPNsense.Timeout.Duration = 8 * time.Second
	}
	if c.OPNsense.Alias.Type == "" {
		c.OPNsense.Alias.Type = "host"
	}
	if c.OPNsense.Alias.Description == "" {
		c.OPNsense.Alias.Description = "Managed by caddy-opnsense-blocker"
	}
	if c.OPNsense.APIPaths.AliasGetUUID == "" {
		c.OPNsense.APIPaths.AliasGetUUID = "/api/firewall/alias/get_alias_u_u_i_d/{alias}"
	}
	if c.OPNsense.APIPaths.AliasAddItem == "" {
		c.OPNsense.APIPaths.AliasAddItem = "/api/firewall/alias/add_item"
	}
	if c.OPNsense.APIPaths.AliasSetItem == "" {
		c.OPNsense.APIPaths.AliasSetItem = "/api/firewall/alias/set_item/{uuid}"
	}
	if c.OPNsense.APIPaths.AliasReconfig == "" {
		c.OPNsense.APIPaths.AliasReconfig = "/api/firewall/alias/reconfigure"
	}
	if c.OPNsense.APIPaths.AliasUtilList == "" {
		c.OPNsense.APIPaths.AliasUtilList = "/api/firewall/alias_util/list/{alias}"
	}
	if c.OPNsense.APIPaths.AliasUtilAdd == "" {
		c.OPNsense.APIPaths.AliasUtilAdd = "/api/firewall/alias_util/add/{alias}"
	}
	if c.OPNsense.APIPaths.AliasUtilDelete == "" {
		c.OPNsense.APIPaths.AliasUtilDelete = "/api/firewall/alias_util/delete/{alias}"
	}
	if !c.OPNsense.EnsureAlias {
		c.OPNsense.EnsureAlias = true
	}

	for name, profile := range c.Profiles {
		if profile.MinStatus == 0 {
			profile.MinStatus = 400
		}
		if profile.MaxStatus == 0 {
			profile.MaxStatus = 599
		}
		profile.normalizedAllowedPostPaths = make(map[string]struct{}, len(profile.AllowedPostPaths))
		for _, path := range profile.AllowedPostPaths {
			profile.normalizedAllowedPostPaths[normalizePath(path)] = struct{}{}
		}
		profile.normalizedSuspiciousPaths = make([]string, 0, len(profile.SuspiciousPathPrefixes))
		for _, prefix := range profile.SuspiciousPathPrefixes {
			profile.normalizedSuspiciousPaths = append(profile.normalizedSuspiciousPaths, normalizePrefix(prefix))
		}
		sort.Strings(profile.normalizedSuspiciousPaths)

		for _, cidr := range profile.ExcludedCIDRs {
			_, network, err := net.ParseCIDR(strings.TrimSpace(cidr))
			if err != nil {
				return fmt.Errorf("profile %q has invalid excluded_cidr %q: %w", name, cidr, err)
			}
			profile.excludedNetworks = append(profile.excludedNetworks, network)
		}

		for index, rule := range profile.KnownAgents {
			decision := strings.ToLower(strings.TrimSpace(rule.Decision))
			profile.KnownAgents[index].Decision = decision
			for _, prefix := range rule.UserAgentPrefixes {
				normalized := strings.ToLower(strings.TrimSpace(prefix))
				if normalized != "" {
					profile.KnownAgents[index].normalizedPrefixes = append(profile.KnownAgents[index].normalizedPrefixes, normalized)
				}
			}
			for _, cidr := range rule.CIDRs {
				_, network, err := net.ParseCIDR(strings.TrimSpace(cidr))
				if err != nil {
					return fmt.Errorf("profile %q rule %q has invalid cidr %q: %w", name, rule.Name, cidr, err)
				}
				profile.KnownAgents[index].networks = append(profile.KnownAgents[index].networks, network)
			}
		}

		c.Profiles[name] = profile
	}

	for index := range c.Sources {
		c.Sources[index].InitialPosition = strings.ToLower(strings.TrimSpace(c.Sources[index].InitialPosition))
		if c.Sources[index].InitialPosition == "" {
			c.Sources[index].InitialPosition = "end"
		}
		if c.Sources[index].PollInterval.Duration == 0 {
			c.Sources[index].PollInterval.Duration = time.Second
		}
		if c.Sources[index].BatchSize <= 0 {
			c.Sources[index].BatchSize = 256
		}
	}

	return nil
}

func (c *Config) validate(sourcePath string) error {
	if len(c.Profiles) == 0 {
		return errors.New("at least one profile is required")
	}
	if len(c.Sources) == 0 {
		return errors.New("at least one source is required")
	}
	if _, _, err := net.SplitHostPort(c.Server.ListenAddress); err != nil {
		return fmt.Errorf("invalid server.listen_address: %w", err)
	}
	if err := os.MkdirAll(filepath.Dir(c.Storage.Path), 0o755); err != nil {
		return fmt.Errorf("prepare storage directory: %w", err)
	}

	seenNames := map[string]struct{}{}
	seenPaths := map[string]struct{}{}
	for _, source := range c.Sources {
		if source.Name == "" {
			return errors.New("source.name must not be empty")
		}
		if source.Path == "" {
			return fmt.Errorf("source %q must define a path", source.Name)
		}
		if _, ok := seenNames[source.Name]; ok {
			return fmt.Errorf("duplicate source name %q", source.Name)
		}
		seenNames[source.Name] = struct{}{}
		if _, ok := seenPaths[source.Path]; ok {
			return fmt.Errorf("duplicate source path %q", source.Path)
		}
		seenPaths[source.Path] = struct{}{}
		if _, ok := c.Profiles[source.Profile]; !ok {
			return fmt.Errorf("source %q references unknown profile %q", source.Name, source.Profile)
		}
		if source.InitialPosition != "beginning" && source.InitialPosition != "end" {
			return fmt.Errorf("source %q has invalid initial_position %q", source.Name, source.InitialPosition)
		}
	}

	for name, profile := range c.Profiles {
		if profile.MinStatus < 100 || profile.MinStatus > 599 {
			return fmt.Errorf("profile %q has invalid min_status %d", name, profile.MinStatus)
		}
		if profile.MaxStatus < profile.MinStatus || profile.MaxStatus > 599 {
			return fmt.Errorf("profile %q has invalid max_status %d", name, profile.MaxStatus)
		}
		for _, prefix := range profile.normalizedSuspiciousPaths {
			if prefix == "/" {
				return fmt.Errorf("profile %q has overly broad suspicious path prefix %q", name, prefix)
			}
		}
		for _, rule := range profile.KnownAgents {
			if rule.Decision != "allow" && rule.Decision != "deny" {
				return fmt.Errorf("profile %q known agent %q has invalid decision %q", name, rule.Name, rule.Decision)
			}
			if len(rule.normalizedPrefixes) == 0 && len(rule.networks) == 0 {
				return fmt.Errorf("profile %q known agent %q must define user_agent_prefixes and/or cidrs", name, rule.Name)
			}
		}
	}

	if c.OPNsense.Enabled {
		if c.OPNsense.BaseURL == "" {
			return errors.New("opnsense.base_url is required when opnsense is enabled")
		}
		if c.OPNsense.Alias.Name == "" {
			return errors.New("opnsense.alias.name is required when opnsense is enabled")
		}
		if c.OPNsense.APIKey == "" && c.OPNsense.APIKeyFile == "" {
			return errors.New("opnsense.api_key or opnsense.api_key_file is required when opnsense is enabled")
		}
		if c.OPNsense.APISecret == "" && c.OPNsense.APISecretFile == "" {
			return errors.New("opnsense.api_secret or opnsense.api_secret_file is required when opnsense is enabled")
		}
		if c.OPNsense.APIKey == "" {
			payload, err := os.ReadFile(c.OPNsense.APIKeyFile)
			if err != nil {
				return fmt.Errorf("read opnsense.api_key_file: %w", err)
			}
			c.OPNsense.APIKey = strings.TrimSpace(string(payload))
		}
		if c.OPNsense.APISecret == "" {
			payload, err := os.ReadFile(c.OPNsense.APISecretFile)
			if err != nil {
				return fmt.Errorf("read opnsense.api_secret_file: %w", err)
			}
			c.OPNsense.APISecret = strings.TrimSpace(string(payload))
		}
	}

	_ = sourcePath
	return nil
}

func normalizePath(input string) string {
	value := strings.TrimSpace(input)
	if value == "" {
		return "/"
	}
	value = strings.SplitN(value, "?", 2)[0]
	value = strings.SplitN(value, "#", 2)[0]
	if !strings.HasPrefix(value, "/") {
		value = "/" + value
	}
	if value != "/" {
		value = strings.TrimRight(value, "/")
	}
	return strings.ToLower(value)
}

func normalizePrefix(input string) string {
	return normalizePath(input)
}

func (p ProfileConfig) IsExcluded(ip net.IP) bool {
	for _, network := range p.excludedNetworks {
		if network.Contains(ip) {
			return true
		}
	}
	return false
}

func (p ProfileConfig) IsAllowedPostPath(path string) bool {
	_, ok := p.normalizedAllowedPostPaths[normalizePath(path)]
	return ok
}

func (p ProfileConfig) SuspiciousPrefixes() []string {
	return append([]string(nil), p.normalizedSuspiciousPaths...)
}

func (p ProfileConfig) MatchKnownAgent(ip net.IP, userAgent string) (KnownAgentRule, bool) {
	normalizedUA := strings.ToLower(strings.TrimSpace(userAgent))
	for _, rule := range p.KnownAgents {
		uaMatched := len(rule.normalizedPrefixes) == 0
		for _, prefix := range rule.normalizedPrefixes {
			if strings.HasPrefix(normalizedUA, prefix) {
				uaMatched = true
				break
			}
		}
		if !uaMatched {
			continue
		}
		cidrMatched := len(rule.networks) == 0
		for _, network := range rule.networks {
			if network.Contains(ip) {
				cidrMatched = true
				break
			}
		}
		if cidrMatched {
			return rule, true
		}
	}
	return KnownAgentRule{}, false
}