use clap::Parser;
use ipnetwork::IpNetwork;
use regex::Regex;
use serde::{Deserialize, Serialize};
use std::env;
use std::fs;
use std::net::IpAddr;
use std::path::{Path, PathBuf};

// Command-line arguments using clap
#[derive(Parser, Debug, Clone)]
#[clap(
    author,
    version,
    about = "Markov chain based HTTP tarpit/honeypot that delays and tracks potential attackers"
)]
pub struct Args {
    #[clap(
        long,
        default_value = "0.0.0.0:8888",
        help = "Address and port to listen for incoming HTTP requests (format: ip:port)"
    )]
    pub listen_addr: String,

    #[clap(
        long,
        default_value = "0.0.0.0:9100",
        help = "Address and port to expose Prometheus metrics and status endpoint (format: ip:port)"
    )]
    pub metrics_addr: String,

    #[clap(long, help = "Disable Prometheus metrics server completely")]
    pub disable_metrics: bool,

    #[clap(
        long,
        default_value = "127.0.0.1:80",
        help = "Backend server address to proxy legitimate requests to (format: ip:port)"
    )]
    pub backend_addr: String,

    #[clap(
        long,
        default_value = "1000",
        help = "Minimum delay in milliseconds between chunks sent to attacker"
    )]
    pub min_delay: u64,

    #[clap(
        long,
        default_value = "15000",
        help = "Maximum delay in milliseconds between chunks sent to attacker"
    )]
    pub max_delay: u64,

    #[clap(
        long,
        default_value = "600",
        help = "Maximum time in seconds to keep an attacker in the tarpit before disconnecting"
    )]
    pub max_tarpit_time: u64,

    #[clap(
        long,
        default_value = "3",
        help = "Number of hits to honeypot patterns before permanently blocking an IP"
    )]
    pub block_threshold: u32,

    #[clap(
        long,
        help = "Base directory for all application data (overrides XDG directory structure)"
    )]
    pub base_dir: Option<PathBuf>,

    #[clap(
        long,
        help = "Path to configuration file (JSON or TOML, overrides command line options)"
    )]
    pub config_file: Option<PathBuf>,

    #[clap(
        long,
        default_value = "info",
        help = "Log level: trace, debug, info, warn, error"
    )]
    pub log_level: String,

    #[clap(
        long,
        default_value = "pretty",
        help = "Log format: plain, pretty, json, pretty-json"
    )]
    pub log_format: String,
}

#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Default)]
pub enum LogFormat {
    Plain,
    #[default]
    Pretty,
    Json,
    PrettyJson,
}

// Trap pattern structure. It can be either a plain string
// regex to catch more advanced patterns necessitated by
// more sophisticated crawlers.
#[derive(Clone, Debug, Deserialize, Serialize)]
#[serde(untagged)]
pub enum TrapPattern {
    Plain(String),
    Regex { pattern: String, regex: bool },
}

impl TrapPattern {
    pub fn as_plain(value: &str) -> Self {
        Self::Plain(value.to_string())
    }

    pub fn as_regex(value: &str) -> Self {
        Self::Regex {
            pattern: value.to_string(),
            regex: true,
        }
    }

    pub fn matches(&self, path: &str) -> bool {
        match self {
            Self::Plain(pattern) => path.contains(pattern),
            Self::Regex {
                pattern,
                regex: true,
            } => {
                if let Ok(re) = Regex::new(pattern) {
                    re.is_match(path)
                } else {
                    false
                }
            }
            _ => false,
        }
    }
}

// Configuration structure
#[derive(Clone, Debug, Deserialize, Serialize)]
pub struct Config {
    pub listen_addr: String,
    pub metrics_addr: String,
    pub disable_metrics: bool,
    pub backend_addr: String,
    pub min_delay: u64,
    pub max_delay: u64,
    pub max_tarpit_time: u64,
    pub block_threshold: u32,
    pub trap_patterns: Vec<TrapPattern>,
    pub whitelist_networks: Vec<String>,
    pub markov_corpora_dir: String,
    pub lua_scripts_dir: String,
    pub data_dir: String,
    pub config_dir: String,
    pub cache_dir: String,
    pub log_format: LogFormat,
}

impl Default for Config {
    fn default() -> Self {
        Self {
            listen_addr: "0.0.0.0:8888".to_string(),
            metrics_addr: "0.0.0.0:9100".to_string(),
            disable_metrics: false,
            backend_addr: "127.0.0.1:80".to_string(),
            min_delay: 1000,
            max_delay: 15000,
            max_tarpit_time: 600,
            block_threshold: 3,
            trap_patterns: vec![
                // Basic attack patterns as plain strings
                TrapPattern::as_plain("/vendor/phpunit"),
                TrapPattern::as_plain("eval-stdin.php"),
                TrapPattern::as_plain("/wp-admin"),
                TrapPattern::as_plain("/wp-login.php"),
                TrapPattern::as_plain("/xmlrpc.php"),
                TrapPattern::as_plain("/phpMyAdmin"),
                TrapPattern::as_plain("/solr/"),
                TrapPattern::as_plain("/.env"),
                TrapPattern::as_plain("/config"),
                TrapPattern::as_plain("/actuator/"),
                // More aggressive patterns for various PHP exploits.
                // XXX: I dedicate this entire section to that one single crawler
                // that has been scanning my entire network, hitting 403s left and right
                // but not giving up, and coming back the next day at the same time to
                // scan the same paths over and over. Kudos to you, random crawler.
                TrapPattern::as_regex(r"/.*phpunit.*eval-stdin\.php"),
                TrapPattern::as_regex(r"/index\.php\?s=/index/\\think\\app/invokefunction"),
                TrapPattern::as_regex(r".*%ADd\+auto_prepend_file%3dphp://input.*"),
                TrapPattern::as_regex(r".*%ADd\+allow_url_include%3d1.*"),
                TrapPattern::as_regex(r".*/wp-content/plugins/.*\.php"),
                TrapPattern::as_regex(r".*/wp-content/themes/.*\.php"),
                TrapPattern::as_regex(r".*eval\(.*\).*"),
                TrapPattern::as_regex(r".*/adminer\.php.*"),
                TrapPattern::as_regex(r".*/admin\.php.*"),
                TrapPattern::as_regex(r".*/administrator/.*"),
                TrapPattern::as_regex(r".*/wp-json/.*"),
                TrapPattern::as_regex(r".*/api/.*\.php.*"),
                TrapPattern::as_regex(r".*/cgi-bin/.*"),
                TrapPattern::as_regex(r".*/owa/.*"),
                TrapPattern::as_regex(r".*/ecp/.*"),
                TrapPattern::as_regex(r".*/webshell\.php.*"),
                TrapPattern::as_regex(r".*/shell\.php.*"),
                TrapPattern::as_regex(r".*/cmd\.php.*"),
                TrapPattern::as_regex(r".*/struts.*"),
            ],
            whitelist_networks: vec![
                "192.168.0.0/16".to_string(),
                "10.0.0.0/8".to_string(),
                "172.16.0.0/12".to_string(),
                "127.0.0.0/8".to_string(),
            ],
            markov_corpora_dir: "./corpora".to_string(),
            lua_scripts_dir: "./scripts".to_string(),
            data_dir: "./data".to_string(),
            config_dir: "./conf".to_string(),
            cache_dir: "./cache".to_string(),
            log_format: LogFormat::Pretty,
        }
    }
}

// Gets standard XDG directory paths for config, data and cache.
// XXX: This could be "simplified" by using the Dirs crate, but I can't
// really justify pulling a library for something I can handle in less
// than 30 lines. Unless cross-platform becomes necessary, the below
// implementation is good enough. For alternative platforms, we can simply
// enhance the current implementation as needed.
pub fn get_xdg_dirs() -> (PathBuf, PathBuf, PathBuf) {
    let config_home = env::var_os("XDG_CONFIG_HOME")
        .map(PathBuf::from)
        .unwrap_or_else(|| {
            let home = env::var_os("HOME").map_or_else(|| PathBuf::from("."), PathBuf::from);
            home.join(".config")
        });

    let data_home = env::var_os("XDG_DATA_HOME")
        .map(PathBuf::from)
        .unwrap_or_else(|| {
            let home = env::var_os("HOME").map_or_else(|| PathBuf::from("."), PathBuf::from);
            home.join(".local").join("share")
        });

    let cache_home = env::var_os("XDG_CACHE_HOME")
        .map(PathBuf::from)
        .unwrap_or_else(|| {
            let home = env::var_os("HOME").map_or_else(|| PathBuf::from("."), PathBuf::from);
            home.join(".cache")
        });

    let config_dir = config_home.join("eris");
    let data_dir = data_home.join("eris");
    let cache_dir = cache_home.join("eris");

    (config_dir, data_dir, cache_dir)
}

impl Config {
    // Create configuration from command-line args. We'll be falling back to this
    // when the configuration is invalid, so it must be validated more strictly.
    pub fn from_args(args: &Args) -> Self {
        let (config_dir, data_dir, cache_dir) = if let Some(base_dir) = &args.base_dir {
            let base_str = base_dir.to_string_lossy().to_string();
            (
                format!("{base_str}/conf"),
                format!("{base_str}/data"),
                format!("{base_str}/cache"),
            )
        } else {
            let (c, d, cache) = get_xdg_dirs();
            (
                c.to_string_lossy().to_string(),
                d.to_string_lossy().to_string(),
                cache.to_string_lossy().to_string(),
            )
        };

        Self {
            listen_addr: args.listen_addr.clone(),
            metrics_addr: args.metrics_addr.clone(),
            disable_metrics: args.disable_metrics,
            backend_addr: args.backend_addr.clone(),
            min_delay: args.min_delay,
            max_delay: args.max_delay,
            max_tarpit_time: args.max_tarpit_time,
            block_threshold: args.block_threshold,
            markov_corpora_dir: format!("{data_dir}/corpora"),
            lua_scripts_dir: format!("{data_dir}/scripts"),
            data_dir,
            config_dir,
            cache_dir,
            ..Default::default()
        }
    }

    // Load configuration from a file (JSON or TOML)
    pub fn load_from_file(path: &Path) -> std::io::Result<Self> {
        let content = fs::read_to_string(path)?;

        let extension = path
            .extension()
            .map(|ext| ext.to_string_lossy().to_lowercase())
            .unwrap_or_default();

        let config = match extension.as_str() {
            "toml" => toml::from_str(&content).map_err(|e| {
                std::io::Error::new(
                    std::io::ErrorKind::InvalidData,
                    format!("Failed to parse TOML: {e}"),
                )
            })?,
            _ => {
                // Default to JSON for any other extension
                serde_json::from_str(&content).map_err(|e| {
                    std::io::Error::new(
                        std::io::ErrorKind::InvalidData,
                        format!("Failed to parse JSON: {e}"),
                    )
                })?
            }
        };

        Ok(config)
    }

    // Save configuration to a file (JSON or TOML)
    pub fn save_to_file(&self, path: &Path) -> std::io::Result<()> {
        if let Some(parent) = path.parent() {
            fs::create_dir_all(parent)?;
        }

        let extension = path
            .extension()
            .map(|ext| ext.to_string_lossy().to_lowercase())
            .unwrap_or_default();

        let content = match extension.as_str() {
            "toml" => toml::to_string_pretty(self).map_err(|e| {
                std::io::Error::new(
                    std::io::ErrorKind::InvalidData,
                    format!("Failed to serialize to TOML: {e}"),
                )
            })?,
            _ => {
                // Default to JSON for any other extension
                serde_json::to_string_pretty(self).map_err(|e| {
                    std::io::Error::new(
                        std::io::ErrorKind::InvalidData,
                        format!("Failed to serialize to JSON: {e}"),
                    )
                })?
            }
        };

        fs::write(path, content)?;
        Ok(())
    }

    // Create required directories if they don't exist
    pub fn ensure_dirs_exist(&self) -> std::io::Result<()> {
        let dirs = [
            &self.markov_corpora_dir,
            &self.lua_scripts_dir,
            &self.data_dir,
            &self.config_dir,
            &self.cache_dir,
        ];

        for dir in dirs {
            fs::create_dir_all(dir)?;
            log::debug!("Created directory: {dir}");
        }

        Ok(())
    }
}

// Decide if a request should be tarpitted based on path and IP
pub fn should_tarpit(path: &str, ip: &IpAddr, config: &Config) -> bool {
    // Check whitelist IPs first to avoid unnecessary pattern matching
    for network_str in &config.whitelist_networks {
        if let Ok(network) = network_str.parse::<IpNetwork>() {
            if network.contains(*ip) {
                return false;
            }
        }
    }

    // Use pattern matching based on the trap pattern type. It can be
    // a plain string or regex.
    for pattern in &config.trap_patterns {
        if pattern.matches(path) {
            return true;
        }
    }

    false
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::net::{IpAddr, Ipv4Addr};

    #[test]
    fn test_config_from_args() {
        let args = Args {
            listen_addr: "127.0.0.1:8080".to_string(),
            metrics_addr: "127.0.0.1:9000".to_string(),
            disable_metrics: true,
            backend_addr: "127.0.0.1:8081".to_string(),
            min_delay: 500,
            max_delay: 10000,
            max_tarpit_time: 300,
            block_threshold: 5,
            base_dir: Some(PathBuf::from("/tmp/eris")),
            config_file: None,
            log_level: "debug".to_string(),
            log_format: "pretty".to_string(),
        };

        let config = Config::from_args(&args);
        assert_eq!(config.listen_addr, "127.0.0.1:8080");
        assert_eq!(config.metrics_addr, "127.0.0.1:9000");
        assert!(config.disable_metrics);
        assert_eq!(config.backend_addr, "127.0.0.1:8081");
        assert_eq!(config.min_delay, 500);
        assert_eq!(config.max_delay, 10000);
        assert_eq!(config.max_tarpit_time, 300);
        assert_eq!(config.block_threshold, 5);
        assert_eq!(config.markov_corpora_dir, "/tmp/eris/data/corpora");
        assert_eq!(config.lua_scripts_dir, "/tmp/eris/data/scripts");
        assert_eq!(config.data_dir, "/tmp/eris/data");
        assert_eq!(config.config_dir, "/tmp/eris/conf");
        assert_eq!(config.cache_dir, "/tmp/eris/cache");
    }

    #[test]
    fn test_trap_pattern_matching() {
        // Test plain string pattern
        let plain = TrapPattern::as_plain("phpunit");
        assert!(plain.matches("path/to/phpunit/test"));
        assert!(!plain.matches("path/to/something/else"));

        // Test regex pattern
        let regex = TrapPattern::as_regex(r".*eval-stdin\.php.*");
        assert!(regex.matches("/vendor/phpunit/phpunit/src/Util/PHP/eval-stdin.php"));
        assert!(regex.matches("/tests/eval-stdin.php?param"));
        assert!(!regex.matches("/normal/path"));

        // Test invalid regex pattern (should return false)
        let invalid = TrapPattern::Regex {
            pattern: "(invalid[regex".to_string(),
            regex: true,
        };
        assert!(!invalid.matches("anything"));
    }

    #[tokio::test]
    async fn test_should_tarpit() {
        let config = Config::default();

        // Test trap patterns
        assert!(should_tarpit(
            "/vendor/phpunit/whatever",
            &IpAddr::V4(Ipv4Addr::new(1, 2, 3, 4)),
            &config
        ));
        assert!(should_tarpit(
            "/wp-admin/login.php",
            &IpAddr::V4(Ipv4Addr::new(1, 2, 3, 4)),
            &config
        ));
        assert!(should_tarpit(
            "/.env",
            &IpAddr::V4(Ipv4Addr::new(1, 2, 3, 4)),
            &config
        ));

        // Test whitelist networks
        assert!(!should_tarpit(
            "/wp-admin/login.php",
            &IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)),
            &config
        ));
        assert!(!should_tarpit(
            "/vendor/phpunit/whatever",
            &IpAddr::V4(Ipv4Addr::new(192, 168, 1, 1)),
            &config
        ));

        // Test legitimate paths
        assert!(!should_tarpit(
            "/index.html",
            &IpAddr::V4(Ipv4Addr::new(1, 2, 3, 4)),
            &config
        ));
        assert!(!should_tarpit(
            "/images/logo.png",
            &IpAddr::V4(Ipv4Addr::new(1, 2, 3, 4)),
            &config
        ));

        // Test regex patterns
        assert!(should_tarpit(
            "/index.php?s=/index/\\think\\app/invokefunction&function=call_user_func_array&vars[0]=md5&vars[1][]=Hello",
            &IpAddr::V4(Ipv4Addr::new(1, 2, 3, 4)),
            &config
        ));

        assert!(should_tarpit(
            "/hello.world?%ADd+allow_url_include%3d1+%ADd+auto_prepend_file%3dphp://input",
            &IpAddr::V4(Ipv4Addr::new(1, 2, 3, 4)),
            &config
        ));
    }

    #[test]
    fn test_config_file_formats() {
        // Create temporary JSON config file
        let temp_dir = std::env::temp_dir();
        let json_path = temp_dir.join("temp_config.json");
        let toml_path = temp_dir.join("temp_config.toml");

        let config = Config::default();

        // Test JSON serialization and deserialization
        config.save_to_file(&json_path).unwrap();
        let loaded_json = Config::load_from_file(&json_path).unwrap();
        assert_eq!(loaded_json.listen_addr, config.listen_addr);
        assert_eq!(loaded_json.min_delay, config.min_delay);

        // Test TOML serialization and deserialization
        config.save_to_file(&toml_path).unwrap();
        let loaded_toml = Config::load_from_file(&toml_path).unwrap();
        assert_eq!(loaded_toml.listen_addr, config.listen_addr);
        assert_eq!(loaded_toml.min_delay, config.min_delay);

        // Clean up
        let _ = std::fs::remove_file(json_path);
        let _ = std::fs::remove_file(toml_path);
    }
}