use std::net::{TcpStream, ToSocketAddrs};
use std::path::PathBuf;
use std::process::Command;
use std::time::Duration;

use serde::Serialize;

// ── URL parsing helpers ──

/// Extract the hostname from a URL like `http://gpu-server:11434`.
/// Handles bracketed IPv6 addresses like `http://[::1]:11434`.
fn extract_host(base_url: &str) -> &str {
    let without_scheme = base_url
        .strip_prefix("http://")
        .or_else(|| base_url.strip_prefix("https://"))
        .unwrap_or(base_url);
    // Handle bracketed IPv6: [::1]:port
    if without_scheme.starts_with('[') {
        return without_scheme
            .find(']')
            .map_or(without_scheme, |end| &without_scheme[..=end]);
    }
    // Take host part (before port colon or path slash)
    let host = without_scheme.split(':').next().unwrap_or(without_scheme);
    host.split('/').next().unwrap_or(host)
}

/// Extract port from a URL like `http://localhost:11434`.
/// Handles trailing paths and slashes (e.g. `http://host:8080/api`).
fn extract_port(base_url: &str) -> u16 {
    base_url
        .rsplit(':')
        .next()
        .and_then(|s| {
            // Strip any path/fragment after the port digits
            let port_str = s.split('/').next().unwrap_or(s);
            port_str.parse().ok()
        })
        .unwrap_or(11434)
}

/// Is this URL pointing at the local machine?
fn is_local_url(base_url: &str) -> bool {
    let host = extract_host(base_url);
    matches!(host, "localhost" | "127.0.0.1" | "::1" | "[::1]")
}

// ── Detection (sync, fast) ──

/// Find the `ollama` binary. Checks PATH first, then well-known locations
/// as fallback for cron/launchd contexts where PATH is minimal.
pub fn find_ollama_binary() -> Option<PathBuf> {
    let from_path = Command::new("which")
        .arg("ollama")
        .output()
        .ok()
        .filter(|o| o.status.success())
        .map(|o| PathBuf::from(String::from_utf8_lossy(&o.stdout).trim().to_string()));

    if from_path.is_some() {
        return from_path;
    }

    const WELL_KNOWN: &[&str] = &[
        "/opt/homebrew/bin/ollama",
        "/usr/local/bin/ollama",
        "/usr/bin/ollama",
        "/snap/bin/ollama",
    ];

    WELL_KNOWN
        .iter()
        .map(PathBuf::from)
        .find(|p| p.is_file())
}

/// TCP-connect to Ollama's port. Tries all resolved addresses (IPv4/IPv6)
/// since `localhost` resolves to `::1` first on macOS but Ollama only
/// listens on `127.0.0.1`.
pub fn is_ollama_reachable(base_url: &str) -> bool {
    let port = extract_port(base_url);
    let host = extract_host(base_url);
    let addr_str = format!("{host}:{port}");

    let Ok(addrs) = addr_str.to_socket_addrs() else {
        return false;
    };
    addrs
        .into_iter()
        .any(|addr| TcpStream::connect_timeout(&addr, Duration::from_secs(2)).is_ok())
}

/// Platform-appropriate installation instructions.
pub fn install_instructions() -> &'static str {
    if cfg!(target_os = "macos") {
        "Install Ollama: brew install ollama  (or https://ollama.ai/download)"
    } else if cfg!(target_os = "linux") {
        "Install Ollama: curl -fsSL https://ollama.ai/install.sh | sh"
    } else {
        "Install Ollama: https://ollama.ai/download"
    }
}

// ── Ensure (spawns ollama if needed) ──

#[derive(Debug, Serialize)]
pub struct OllamaEnsureResult {
    pub installed: bool,
    pub was_running: bool,
    pub started: bool,
    pub running: bool,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub error: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub install_hint: Option<String>,
}

/// Ensure Ollama is available. For local URLs, spawns `ollama serve` if
/// not already running. For remote URLs, only checks reachability.
///
/// Waits briefly (5s) for hot restarts; cold starts finish during the
/// ingestion phase (~90s) before the embed stage needs Ollama.
pub fn ensure_ollama(base_url: &str) -> OllamaEnsureResult {
    let is_local = is_local_url(base_url);

    let binary_path = if is_local {
        let path = find_ollama_binary();
        if path.is_none() {
            return OllamaEnsureResult {
                installed: false,
                was_running: false,
                started: false,
                running: false,
                error: Some("Ollama is not installed".to_string()),
                install_hint: Some(install_instructions().to_string()),
            };
        }
        path
    } else {
        None
    };

    if is_ollama_reachable(base_url) {
        return OllamaEnsureResult {
            installed: true,
            was_running: true,
            started: false,
            running: true,
            error: None,
            install_hint: None,
        };
    }

    if !is_local {
        return OllamaEnsureResult {
            installed: true,
            was_running: false,
            started: false,
            running: false,
            error: Some(format!(
                "Ollama at {base_url} is not reachable (remote — cannot auto-start)"
            )),
            install_hint: None,
        };
    }

    // Spawn using the absolute path (cron PATH won't include Homebrew etc.)
    let ollama_bin = binary_path.expect("binary_path is Some for local URLs after binary check");
    let spawn_result = Command::new(&ollama_bin)
        .arg("serve")
        .stdout(std::process::Stdio::null())
        .stderr(std::process::Stdio::null())
        .spawn();

    if let Err(e) = spawn_result {
        return OllamaEnsureResult {
            installed: true,
            was_running: false,
            started: false,
            running: false,
            error: Some(format!("Failed to spawn 'ollama serve': {e}")),
            install_hint: None,
        };
    }

    // Brief poll for hot restarts; cold starts finish during ingestion.
    for _ in 0..10 {
        std::thread::sleep(Duration::from_millis(500));
        if is_ollama_reachable(base_url) {
            return OllamaEnsureResult {
                installed: true,
                was_running: false,
                started: true,
                running: true,
                error: None,
                install_hint: None,
            };
        }
    }

    OllamaEnsureResult {
        installed: true,
        was_running: false,
        started: true,
        running: false,
        error: None,
        install_hint: None,
    }
}

// ── Brief status (for cron status display) ──

/// Lightweight status snapshot for display in `cron status`.
#[derive(Debug, Clone, Serialize)]
pub struct OllamaStatusBrief {
    pub installed: bool,
    pub running: bool,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub binary_path: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub install_hint: Option<String>,
}

/// Quick, non-blocking Ollama status check for display purposes.
pub fn ollama_status_brief(base_url: &str) -> OllamaStatusBrief {
    let is_local = is_local_url(base_url);

    // For remote URLs, only check reachability (binary check is irrelevant)
    if !is_local {
        let running = is_ollama_reachable(base_url);
        return OllamaStatusBrief {
            installed: true, // unknown for remote, but not actionable
            running,
            binary_path: None,
            install_hint: None,
        };
    }

    let binary_path = find_ollama_binary();
    let installed = binary_path.is_some();

    if !installed {
        return OllamaStatusBrief {
            installed: false,
            running: false,
            binary_path: None,
            install_hint: Some(install_instructions().to_string()),
        };
    }

    let running = is_ollama_reachable(base_url);

    OllamaStatusBrief {
        installed: true,
        running,
        binary_path: binary_path.map(|p| p.display().to_string()),
        install_hint: None,
    }
}

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

    // ── URL parsing ──

    #[test]
    fn extract_port_default_url() {
        assert_eq!(extract_port("http://localhost:11434"), 11434);
    }

    #[test]
    fn extract_port_custom() {
        assert_eq!(extract_port("http://192.168.1.5:9999"), 9999);
    }

    #[test]
    fn extract_port_trailing_slash() {
        assert_eq!(extract_port("http://localhost:11434/"), 11434);
    }

    #[test]
    fn extract_port_with_path() {
        assert_eq!(extract_port("http://localhost:8080/api/generate"), 8080);
    }

    #[test]
    fn extract_port_no_port() {
        assert_eq!(extract_port("http://localhost"), 11434);
    }

    #[test]
    fn extract_port_https() {
        assert_eq!(extract_port("https://ollama.internal:8080"), 8080);
    }

    #[test]
    fn extract_host_localhost() {
        assert_eq!(extract_host("http://localhost:11434"), "localhost");
    }

    #[test]
    fn extract_host_ip() {
        assert_eq!(extract_host("http://192.168.1.5:9999"), "192.168.1.5");
    }

    #[test]
    fn extract_host_remote() {
        assert_eq!(extract_host("http://gpu-server:11434"), "gpu-server");
    }

    #[test]
    fn extract_host_no_port() {
        assert_eq!(extract_host("http://localhost"), "localhost");
    }

    #[test]
    fn extract_host_https() {
        assert_eq!(
            extract_host("https://ollama.internal:8080"),
            "ollama.internal"
        );
    }

    #[test]
    fn extract_host_no_scheme() {
        assert_eq!(extract_host("localhost:11434"), "localhost");
    }

    // ── is_local_url ──

    #[test]
    fn is_local_url_localhost() {
        assert!(is_local_url("http://localhost:11434"));
    }

    #[test]
    fn is_local_url_loopback() {
        assert!(is_local_url("http://127.0.0.1:11434"));
    }

    #[test]
    fn is_local_url_ipv6_loopback() {
        assert!(is_local_url("http://[::1]:11434"));
    }

    #[test]
    fn is_local_url_remote() {
        assert!(!is_local_url("http://gpu-server:11434"));
        assert!(!is_local_url("http://192.168.1.5:11434"));
    }

    #[test]
    fn is_local_url_fqdn_not_local() {
        assert!(!is_local_url("http://ollama.example.com:11434"));
    }

    // ── install_instructions ──

    #[test]
    fn install_instructions_not_empty() {
        assert!(!install_instructions().is_empty());
        assert!(install_instructions().contains("ollama"));
    }

    #[test]
    fn install_instructions_contains_url() {
        assert!(install_instructions().contains("ollama.ai"));
    }

    // ── is_ollama_reachable ──

    #[test]
    fn reachable_returns_false_for_closed_port() {
        // Port 1 is almost never open and requires root to bind
        assert!(!is_ollama_reachable("http://127.0.0.1:1"));
    }

    #[test]
    fn reachable_returns_false_for_unresolvable_host() {
        assert!(!is_ollama_reachable(
            "http://this-host-does-not-exist-xyzzy:11434"
        ));
    }

    // ── OllamaEnsureResult serialization ──

    #[test]
    fn ensure_result_serializes_installed_running() {
        let result = OllamaEnsureResult {
            installed: true,
            was_running: true,
            started: false,
            running: true,
            error: None,
            install_hint: None,
        };
        let json: serde_json::Value = serde_json::to_value(&result).unwrap();
        assert_eq!(json["installed"], true);
        assert_eq!(json["was_running"], true);
        assert_eq!(json["started"], false);
        assert_eq!(json["running"], true);
        // skip_serializing_if: None fields should be absent
        assert!(json.get("error").is_none());
        assert!(json.get("install_hint").is_none());
    }

    #[test]
    fn ensure_result_serializes_not_installed() {
        let result = OllamaEnsureResult {
            installed: false,
            was_running: false,
            started: false,
            running: false,
            error: Some("Ollama is not installed".to_string()),
            install_hint: Some("Install Ollama: brew install ollama".to_string()),
        };
        let json: serde_json::Value = serde_json::to_value(&result).unwrap();
        assert_eq!(json["installed"], false);
        assert_eq!(json["running"], false);
        assert_eq!(json["error"], "Ollama is not installed");
        assert!(
            json["install_hint"]
                .as_str()
                .unwrap()
                .contains("brew install")
        );
    }

    // ── OllamaStatusBrief serialization ──

    #[test]
    fn status_brief_serializes_with_optional_fields() {
        let brief = OllamaStatusBrief {
            installed: true,
            running: true,
            binary_path: Some("/usr/local/bin/ollama".to_string()),
            install_hint: None,
        };
        let json: serde_json::Value = serde_json::to_value(&brief).unwrap();
        assert_eq!(json["installed"], true);
        assert_eq!(json["running"], true);
        assert_eq!(json["binary_path"], "/usr/local/bin/ollama");
        assert!(json.get("install_hint").is_none());
    }

    #[test]
    fn status_brief_serializes_not_installed() {
        let brief = OllamaStatusBrief {
            installed: false,
            running: false,
            binary_path: None,
            install_hint: Some("Install Ollama".to_string()),
        };
        let json: serde_json::Value = serde_json::to_value(&brief).unwrap();
        assert_eq!(json["installed"], false);
        assert_eq!(json["running"], false);
        assert!(json.get("binary_path").is_none());
        assert_eq!(json["install_hint"], "Install Ollama");
    }

    #[test]
    fn status_brief_clone() {
        let original = OllamaStatusBrief {
            installed: true,
            running: false,
            binary_path: Some("/opt/bin/ollama".to_string()),
            install_hint: None,
        };
        let cloned = original.clone();
        assert_eq!(original.installed, cloned.installed);
        assert_eq!(original.running, cloned.running);
        assert_eq!(original.binary_path, cloned.binary_path);
        assert_eq!(original.install_hint, cloned.install_hint);
    }

    // ── ensure_ollama with remote URL ──

    #[test]
    fn ensure_remote_unreachable_does_not_set_install_hint() {
        // A remote URL that nothing listens on — should NOT suggest local install
        let result = ensure_ollama("http://192.0.2.1:1"); // TEST-NET, will fail fast
        assert!(!result.started);
        assert!(!result.running);
        assert!(
            result.install_hint.is_none(),
            "remote URLs should not suggest local install"
        );
        assert!(
            result.error.as_deref().unwrap_or("").contains("remote"),
            "error should mention 'remote': {:?}",
            result.error,
        );
    }

    // ── ensure_ollama with local URL (binary check) ──

    #[test]
    fn ensure_local_closed_port_not_already_running() {
        // Local URL pointing at a port nothing listens on
        let result = ensure_ollama("http://127.0.0.1:1");
        // Should NOT report was_running since port 1 is closed
        assert!(!result.was_running);
        assert!(!result.running);
        // If ollama binary is not installed, should get install hint
        if !result.installed {
            assert!(result.install_hint.is_some());
            assert!(
                result
                    .error
                    .as_deref()
                    .unwrap_or("")
                    .contains("not installed")
            );
        }
    }
}