/// What the user chose to record. Switching from a window to a monitor always
/// needs the user's choice; the recorder never broadens the target by itself.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum CaptureTarget {
    /// Windows: Game Capture hooked into one game window, the default for games.
    /// Elsewhere this is the same as `Window`.
    Game { window: WindowMatch },
    /// A single window: Windows Window Capture, X11 Xcomposite, or a
    /// PipeWire window stream selected through the desktop portal on Wayland.
    Window { window: WindowMatch },
    /// A whole monitor, including whatever is shown during alt-tab.
    Monitor { monitor: MonitorMatch },
}

/// Identifies a window. On Windows this is OBS's `title:class:executable`
/// string; on X11 it is the Xcomposite window id; on Wayland the portal picks
/// the window, so only `restore_token` matters.
#[derive(Debug, Clone, Default, PartialEq, Eq)]
pub struct WindowMatch {
    pub obs_window: String,
    pub restore_token: Option<String>,
}

#[derive(Debug, Clone, Default, PartialEq, Eq)]
pub struct MonitorMatch {
    /// Windows monitor device id, or X11 screen number; unused on Wayland.
    pub obs_monitor: String,
    pub restore_token: Option<String>,
}

#[derive(Debug, Clone, PartialEq)]
pub enum SettingValue {
    String(String),
    Int(i64),
    Bool(bool),
}

/// An OBS source id with its settings.
#[derive(Debug, Clone, PartialEq)]
pub struct SourceSpec {
    pub id: &'static str,
    pub settings: Vec<(&'static str, SettingValue)>,
}

impl SourceSpec {
    fn new(id: &'static str) -> Self {
        Self {
            id,
            settings: Vec::new(),
        }
    }

    fn with(mut self, key: &'static str, value: SettingValue) -> Self {
        self.settings.push((key, value));
        self
    }
}

/// Which Linux display server the recorder is running under.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum LinuxSession {
    Wayland,
    X11,
}

impl LinuxSession {
    pub fn detect() -> Option<Self> {
        if std::env::var_os("WAYLAND_DISPLAY").is_some() {
            Some(Self::Wayland)
        } else if std::env::var_os("DISPLAY").is_some() {
            Some(Self::X11)
        } else {
            None
        }
    }
}

impl CaptureTarget {
    #[cfg(windows)]
    pub fn video_source(&self) -> SourceSpec {
        // libobs/util/windows/window-helpers.h: CLASS, TITLE, EXE.
        const WINDOW_PRIORITY_EXE: i64 = 2;
        use SettingValue::*;
        match self {
            Self::Game { window } => SourceSpec::new("game_capture")
                .with("capture_mode", String("window".into()))
                .with("window", String(window.obs_window.clone()))
                // Match the executable first: survives title changes.
                .with("priority", Int(WINDOW_PRIORITY_EXE))
                .with("capture_cursor", Bool(false)),
            // Other Game Capture settings, including its anti-cheat
            // compatibility hook, keep OBS's defaults.
            Self::Window { window } => SourceSpec::new("window_capture")
                .with("window", String(window.obs_window.clone()))
                .with("priority", Int(WINDOW_PRIORITY_EXE))
                .with("cursor", Bool(false)),
            Self::Monitor { monitor } => SourceSpec::new("monitor_capture")
                .with("monitor_id", String(monitor.obs_monitor.clone()))
                .with("capture_cursor", Bool(true)),
        }
    }

    #[cfg(not(windows))]
    pub fn video_source(&self, session: LinuxSession) -> SourceSpec {
        use SettingValue::*;
        match (session, self) {
            (LinuxSession::Wayland, Self::Game { window } | Self::Window { window }) => {
                portal_source(
                    "pipewire-window-capture-source",
                    window.restore_token.as_deref(),
                )
            }
            (LinuxSession::Wayland, Self::Monitor { monitor }) => portal_source(
                "pipewire-screen-capture-source",
                monitor.restore_token.as_deref(),
            ),
            (LinuxSession::X11, Self::Game { window } | Self::Window { window }) => {
                SourceSpec::new("xcomposite_input")
                    .with("capture_window", String(window.obs_window.clone()))
                    .with("show_cursor", Bool(false))
            }
            (LinuxSession::X11, Self::Monitor { monitor }) => SourceSpec::new("xshm_input_v2")
                .with("screen", Int(monitor.obs_monitor.parse().unwrap_or(0)))
                .with("show_cursor", Bool(true)),
        }
    }

    pub fn restore_token(&self) -> Option<&str> {
        match self {
            Self::Game { window } | Self::Window { window } => window.restore_token.as_deref(),
            Self::Monitor { monitor } => monitor.restore_token.as_deref(),
        }
    }
}

#[cfg(not(windows))]
fn portal_source(id: &'static str, restore_token: Option<&str>) -> SourceSpec {
    let spec = SourceSpec::new(id).with("ShowCursor", SettingValue::Bool(true));
    match restore_token {
        // Lets the portal restore the earlier selection without asking again.
        Some(token) => spec.with("RestoreToken", SettingValue::String(token.to_owned())),
        None => spec,
    }
}

/// Desktop audio and, when opted in, the default microphone.
pub fn system_audio_source() -> SourceSpec {
    #[cfg(windows)]
    let id = "wasapi_output_capture";
    #[cfg(not(windows))]
    let id = "pulse_output_capture";
    SourceSpec::new(id).with("device_id", SettingValue::String("default".into()))
}

pub fn microphone_source() -> SourceSpec {
    #[cfg(windows)]
    let id = "wasapi_input_capture";
    #[cfg(not(windows))]
    let id = "pulse_input_capture";
    SourceSpec::new(id).with("device_id", SettingValue::String("default".into()))
}

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

    #[cfg(not(windows))]
    #[test]
    fn wayland_monitor_uses_the_portal_and_restores_the_selection() {
        let target = CaptureTarget::Monitor {
            monitor: MonitorMatch {
                obs_monitor: String::new(),
                restore_token: Some("tok".into()),
            },
        };
        let spec = target.video_source(LinuxSession::Wayland);
        assert_eq!(spec.id, "pipewire-screen-capture-source");
        assert!(
            spec.settings
                .contains(&("RestoreToken", SettingValue::String("tok".into())))
        );
    }

    #[cfg(not(windows))]
    #[test]
    fn game_capture_is_window_capture_off_windows() {
        let window = WindowMatch::default();
        let game = CaptureTarget::Game {
            window: window.clone(),
        };
        let plain = CaptureTarget::Window { window };
        for session in [LinuxSession::Wayland, LinuxSession::X11] {
            assert_eq!(game.video_source(session), plain.video_source(session));
        }
    }

    #[cfg(windows)]
    #[test]
    fn game_target_uses_official_game_capture() {
        let target = CaptureTarget::Game {
            window: WindowMatch {
                obs_window: "Game:GameClass:game.exe".into(),
                restore_token: None,
            },
        };
        assert_eq!(target.video_source().id, "game_capture");
    }
}