use colored::*;
use reqwest::blocking;
use reqwest::Url;

/// Where the proxy URL came from — used for status messages.
#[derive(Debug, Clone, PartialEq)]
pub enum ProxySource {
    /// --proxy <url> on the command line
    Flag,
    /// HTTPS_PROXY or HTTP_PROXY environment variable
    Env(String),
}

/// Resolved proxy configuration.  A `None` url means "go direct".
#[derive(Debug, Clone)]
pub struct ProxyConfig {
    pub url: Option<Url>,
    pub source: Option<ProxySource>,
}

impl ProxyConfig {
    /// Resolve proxy with this priority:
    ///   1. --no-proxy          → direct, ignore everything
    ///   2. --proxy <url>       → use that URL
    ///   3. HTTPS_PROXY / HTTP_PROXY env vars
    ///   4. Nothing             → direct
    pub fn resolve(proxy_flag: Option<&str>, no_proxy: bool) -> Result<Self, anyhow::Error> {
        if no_proxy {
            return Ok(Self { url: None, source: None });
        }

        if let Some(raw) = proxy_flag {
            let url = Url::parse(raw)
                .map_err(|e| anyhow::anyhow!("Invalid --proxy URL '{}': {}", raw, e))?;
            return Ok(Self { url: Some(url), source: Some(ProxySource::Flag) });
        }

        // Walk the env vars in priority order
        for var in &["HTTPS_PROXY", "https_proxy", "HTTP_PROXY", "http_proxy"] {
            if let Ok(val) = std::env::var(var) {
                if val.is_empty() { continue; }
                let url = Url::parse(&val)
                    .map_err(|e| anyhow::anyhow!("Invalid {} env var '{}': {}", var, val, e))?;
                return Ok(Self {
                    url: Some(url),
                    source: Some(ProxySource::Env(var.to_string())),
                });
            }
        }

        Ok(Self { url: None, source: None })
    }

    /// True when the user explicitly passed --proxy (as opposed to env-var pickup).
    /// Used for distinguishing "you asked for this proxy and it failed" from
    /// "we picked up an ambient proxy from your environment" in error paths.
    #[allow(dead_code)]
    pub fn is_explicit(&self) -> bool {
        matches!(self.source, Some(ProxySource::Flag))
    }

    /// Human-readable description of where the proxy came from, for status output.
    pub fn source_description(&self) -> String {
        match &self.source {
            Some(ProxySource::Flag) => "--proxy flag".to_string(),
            Some(ProxySource::Env(var)) => format!("{} env var", var),
            None => "none".to_string(),
        }
    }

    /// Print a one-line proxy status line (used in setup output).
    pub fn print_status(&self) {
        match &self.url {
            Some(url) => println!(
                "  {} Proxy: {} ({})",
                "✓".green(),
                url.as_str().bright_white(),
                self.source_description()
            ),
            None => println!(
                "  {} Proxy: direct (no proxy)",
                "○".bright_black()
            ),
        }
    }

    /// Build a reqwest blocking Client that honours this proxy config.
    ///
    /// * `Some(url)` → all HTTP/HTTPS traffic goes through that proxy.
    /// * `None`      → direct, no proxy at all.
    ///
    /// We always go through the builder (never plain `Client::new()`) because
    /// `Client::new()` silently picks up env-var proxies.  When the user says
    /// `--no-proxy` we need to actively disable that.
    pub fn client(&self) -> anyhow::Result<blocking::Client> {
        let mut builder = blocking::ClientBuilder::new();

        match &self.url {
            Some(url) => {
                builder = builder.proxy(reqwest::Proxy::all(url.clone())?);
            }
            None => {
                // Actively suppress env-var auto-detection.
                builder = builder.no_proxy();
            }
        }

        builder.build().map_err(|e| anyhow::anyhow!("Failed to build HTTP client: {}", e))
    }
}

/// RAII guard that temporarily sets HTTPS_PROXY / HTTP_PROXY for the lifetime
/// of the guard, then restores the previous values on drop.
///
/// libgit2 (the C library behind the `git2` crate) reads these env vars
/// directly for its HTTP transport.  This is the cleanest way to make
/// `git2::Repository::clone` and `remote.fetch()` honour a `--proxy` flag
/// without touching the user's global `~/.gitconfig`.
///
/// When the ProxyConfig has no URL (direct / --no-proxy) the guard *clears*
/// the vars so libgit2 won't accidentally pick up an ambient proxy the user
/// didn't intend for this operation.
pub struct GitProxyGuard {
    prev_https: Option<String>,
    prev_http:  Option<String>,
}

impl GitProxyGuard {
    pub fn new(config: &ProxyConfig) -> Self {
        let prev_https = std::env::var("HTTPS_PROXY").ok();
        let prev_http  = std::env::var("HTTP_PROXY").ok();

        match &config.url {
            Some(url) => {
                let s = url.as_str();
                std::env::set_var("HTTPS_PROXY", s);
                std::env::set_var("HTTP_PROXY",  s);
            }
            None => {
                std::env::remove_var("HTTPS_PROXY");
                std::env::remove_var("HTTP_PROXY");
            }
        }

        Self { prev_https, prev_http }
    }
}

impl Drop for GitProxyGuard {
    fn drop(&mut self) {
        match &self.prev_https {
            Some(v) => std::env::set_var("HTTPS_PROXY", v),
            None    => std::env::remove_var("HTTPS_PROXY"),
        }
        match &self.prev_http {
            Some(v) => std::env::set_var("HTTP_PROXY", v),
            None    => std::env::remove_var("HTTP_PROXY"),
        }
    }
}

/// Print clear, actionable instructions for obtaining dependencies without
/// an internet connection.  Called whenever a network download fails so the
/// user always sees their escape hatch.
pub fn print_offline_instructions() {
    println!();
    println!("{}", "── Offline / Air-Gapped Installation ──────────────────────".bright_yellow().bold());
    println!();
    println!("If you have no internet access (or the proxy is not working),");
    println!("you can obtain the required SDKs on a connected machine and");
    println!("copy them over.");
    println!();
    println!("{}", "1. FTC SDK (git clone)".bright_cyan().bold());
    println!("   On a connected machine:");
    println!("     git clone https://github.com/FIRST-Tech-Challenge/FtcRobotController.git");
    println!("     cd FtcRobotController");
    println!("     git checkout v10.1.1");
    println!();
    println!("   Copy the entire FtcRobotController/ directory to this machine");
    println!("   at ~/.weevil/ftc-sdk/  (or wherever your .weevil.toml points).");
    println!();
    println!("{}", "2. Android SDK (command-line tools)".bright_cyan().bold());
    println!("   Download the zip for your OS from a connected machine:");
    println!("     Linux:   https://dl.google.com/android/repository/commandlinetools-linux-11076708_latest.zip");
    println!("     macOS:   https://dl.google.com/android/repository/commandlinetools-mac-11076708_latest.zip");
    println!("     Windows: https://dl.google.com/android/repository/commandlinetools-win-11076708_latest.zip");
    println!();
    println!("   Extract to ~/.weevil/android-sdk/, then run sdkmanager:");
    println!("     ./cmdline-tools/latest/bin/sdkmanager \\");
    println!("       platform-tools platforms;android-34 build-tools;34.0.0");
    println!();
    println!("   Copy the resulting android-sdk/ directory to this machine.");
    println!();
    println!("{}", "3. Gradle distribution".bright_cyan().bold());
    println!("   Gradle fetches its own distribution the first time ./gradlew");
    println!("   runs.  If that fails offline, download manually:");
    println!("     https://services.gradle.org/distributions/gradle-8.9-bin.zip");
    println!("   Extract into ~/.gradle/wrapper/dists/gradle-8.9-bin/");
    println!("   (the exact subdirectory is printed by gradlew on failure).");
    println!();
    println!("{}", "4. Proxy quick reference".bright_cyan().bold());
    println!("   • Use a specific proxy:    weevil --proxy http://proxy:3128 sdk install");
    println!("   • Skip the proxy entirely: weevil --no-proxy sdk install");
    println!("   • Gradle also reads HTTPS_PROXY / HTTP_PROXY, so set those");
    println!("     in your shell before running ./gradlew if the build needs a proxy.");
    println!();
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::sync::Mutex;

    // Env vars are process-global.  cargo test runs tests in parallel within
    // a single binary, so any test that sets/removes HTTPS_PROXY or HTTP_PROXY
    // must hold this lock for its entire duration.
    static ENV_MUTEX: Mutex<()> = Mutex::new(());

    #[test]
    fn no_proxy_flag_forces_direct() {
        let _env_lock = ENV_MUTEX.lock().unwrap();
        std::env::set_var("HTTPS_PROXY", "http://proxy.example.com:3128");
        let config = ProxyConfig::resolve(None, true).unwrap();
        assert!(config.url.is_none());
        std::env::remove_var("HTTPS_PROXY");
    }

    #[test]
    fn explicit_flag_overrides_env() {
        let _env_lock = ENV_MUTEX.lock().unwrap();
        std::env::set_var("HTTPS_PROXY", "http://env-proxy.example.com:3128");
        let config = ProxyConfig::resolve(Some("http://flag-proxy.example.com:8080"), false).unwrap();
        assert_eq!(config.url.as_ref().unwrap().host_str(), Some("flag-proxy.example.com"));
        assert!(config.is_explicit());
        std::env::remove_var("HTTPS_PROXY");
    }

    #[test]
    fn picks_up_env_var() {
        let _env_lock = ENV_MUTEX.lock().unwrap();
        std::env::remove_var("HTTPS_PROXY");
        std::env::remove_var("https_proxy");
        std::env::set_var("HTTP_PROXY", "http://env-proxy.example.com:3128");
        let config = ProxyConfig::resolve(None, false).unwrap();
        assert_eq!(config.url.as_ref().unwrap().host_str(), Some("env-proxy.example.com"));
        assert_eq!(config.source, Some(ProxySource::Env("HTTP_PROXY".to_string())));
        std::env::remove_var("HTTP_PROXY");
    }

    #[test]
    fn direct_when_nothing_set() {
        let _env_lock = ENV_MUTEX.lock().unwrap();
        std::env::remove_var("HTTPS_PROXY");
        std::env::remove_var("https_proxy");
        std::env::remove_var("HTTP_PROXY");
        std::env::remove_var("http_proxy");
        let config = ProxyConfig::resolve(None, false).unwrap();
        assert!(config.url.is_none());
    }

    #[test]
    fn rejects_garbage_url() {
        let result = ProxyConfig::resolve(Some("not a url at all"), false);
        assert!(result.is_err());
    }

    #[test]
    fn client_builds_with_proxy() {
        let config = ProxyConfig::resolve(Some("http://proxy.example.com:3128"), false).unwrap();
        assert!(config.client().is_ok());
    }

    #[test]
    fn client_builds_direct() {
        let _env_lock = ENV_MUTEX.lock().unwrap();
        std::env::remove_var("HTTPS_PROXY");
        std::env::remove_var("https_proxy");
        std::env::remove_var("HTTP_PROXY");
        std::env::remove_var("http_proxy");
        let config = ProxyConfig::resolve(None, true).unwrap();
        assert!(config.client().is_ok());
    }

    #[test]
    fn git_proxy_guard_sets_and_restores() {
        let _env_lock = ENV_MUTEX.lock().unwrap();
        std::env::set_var("HTTPS_PROXY", "http://original:1111");
        std::env::set_var("HTTP_PROXY",  "http://original:2222");

        let config = ProxyConfig::resolve(Some("http://guarded:9999"), false).unwrap();
        {
            let _guard = GitProxyGuard::new(&config);
            // Url::parse normalises — trailing slash is expected
            assert_eq!(std::env::var("HTTPS_PROXY").unwrap(), "http://guarded:9999/");
            assert_eq!(std::env::var("HTTP_PROXY").unwrap(),  "http://guarded:9999/");
        }
        assert_eq!(std::env::var("HTTPS_PROXY").unwrap(), "http://original:1111");
        assert_eq!(std::env::var("HTTP_PROXY").unwrap(),  "http://original:2222");

        std::env::remove_var("HTTPS_PROXY");
        std::env::remove_var("HTTP_PROXY");
    }

    #[test]
    fn git_proxy_guard_clears_for_direct() {
        let _env_lock = ENV_MUTEX.lock().unwrap();
        std::env::set_var("HTTPS_PROXY", "http://should-be-cleared:1111");
        std::env::set_var("HTTP_PROXY",  "http://should-be-cleared:2222");

        let config = ProxyConfig { url: None, source: None };
        {
            let _guard = GitProxyGuard::new(&config);
            assert!(std::env::var("HTTPS_PROXY").is_err());
            assert!(std::env::var("HTTP_PROXY").is_err());
        }
        assert_eq!(std::env::var("HTTPS_PROXY").unwrap(), "http://should-be-cleared:1111");
        assert_eq!(std::env::var("HTTP_PROXY").unwrap(),  "http://should-be-cleared:2222");

        std::env::remove_var("HTTPS_PROXY");
        std::env::remove_var("HTTP_PROXY");
    }
}