use serde::{Deserialize, Serialize};
use std::collections::VecDeque;
use std::fmt::Write as _;

use super::state::{InputRouting, LauncherState, ViewMode};

#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
pub struct PerformanceSample {
    pub rtt_ms: f32,
    pub input_latency_ms: f32,
    pub left_fps: f32,
    pub right_fps: f32,
    pub dropped_frames: u64,
    pub queue_depth: u32,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct DiagnosticsLog {
    capacity: usize,
    history: VecDeque<PerformanceSample>,
}

impl DiagnosticsLog {
    pub fn new(capacity: usize) -> Self {
        let capacity = capacity.max(1);
        Self {
            capacity,
            history: VecDeque::with_capacity(capacity),
        }
    }

    pub fn record(&mut self, sample: PerformanceSample) {
        if self.history.len() == self.capacity {
            let _ = self.history.pop_front();
        }
        self.history.push_back(sample);
    }

    pub fn latest(&self) -> Option<&PerformanceSample> {
        self.history.back()
    }

    pub fn len(&self) -> usize {
        self.history.len()
    }

    pub fn is_empty(&self) -> bool {
        self.history.is_empty()
    }

    pub fn iter(&self) -> impl Iterator<Item = &PerformanceSample> {
        self.history.iter()
    }
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SnapshotReport {
    pub client_version: String,
    pub server_version: Option<String>,
    pub server_available: bool,
    pub routing: InputRouting,
    pub view_mode: ViewMode,
    pub remote_active: bool,
    pub power_state: String,
    pub preview_source: String,
    pub breakout_display: String,
    pub left_surface: String,
    pub left_capture_profile: String,
    pub left_breakout_profile: String,
    pub right_surface: String,
    pub right_capture_profile: String,
    pub right_breakout_profile: String,
    pub selected_camera: Option<String>,
    pub selected_microphone: Option<String>,
    pub selected_speaker: Option<String>,
    pub selected_keyboard: Option<String>,
    pub selected_mouse: Option<String>,
    pub status: String,
    pub recent_samples: Vec<PerformanceSample>,
    pub notes: Vec<String>,
    pub recommendations: Vec<String>,
    pub probe_command: String,
}

impl SnapshotReport {
    pub fn from_state(state: &LauncherState, log: &DiagnosticsLog, probe_command: String) -> Self {
        let left_capture = state.capture_size_choice(0);
        let right_capture = state.capture_size_choice(1);
        let left_breakout = state.breakout_size_choice(0);
        let right_breakout = state.breakout_size_choice(1);
        Self {
            client_version: crate::VERSION.to_string(),
            server_version: state.server_version.clone(),
            server_available: state.server_available,
            routing: state.routing,
            view_mode: state.view_mode,
            remote_active: state.remote_active,
            power_state: format!(
                "{} | {} | leases {}",
                state.capture_power.mode,
                state.capture_power.detail,
                state.capture_power.active_leases
            ),
            preview_source: format!(
                "{}x{} @ {} fps",
                state.preview_source.width, state.preview_source.height, state.preview_source.fps
            ),
            breakout_display: format!(
                "{}x{}",
                state.breakout_display.width, state.breakout_display.height
            ),
            left_surface: state.display_surface(0).label().to_string(),
            left_capture_profile: format!(
                "{} | {}x{} | {} fps | {} kbit",
                left_capture.preset.as_id(),
                left_capture.width,
                left_capture.height,
                left_capture.fps,
                left_capture.max_bitrate_kbit
            ),
            left_breakout_profile: format!(
                "{} | {}x{}",
                left_breakout.preset.as_id(),
                left_breakout.width,
                left_breakout.height
            ),
            right_surface: state.display_surface(1).label().to_string(),
            right_capture_profile: format!(
                "{} | {}x{} | {} fps | {} kbit",
                right_capture.preset.as_id(),
                right_capture.width,
                right_capture.height,
                right_capture.fps,
                right_capture.max_bitrate_kbit
            ),
            right_breakout_profile: format!(
                "{} | {}x{}",
                right_breakout.preset.as_id(),
                right_breakout.width,
                right_breakout.height
            ),
            selected_camera: state.devices.camera.clone(),
            selected_microphone: state.devices.microphone.clone(),
            selected_speaker: state.devices.speaker.clone(),
            selected_keyboard: state.devices.keyboard.clone(),
            selected_mouse: state.devices.mouse.clone(),
            status: state.status_line(),
            recent_samples: log.iter().cloned().collect(),
            notes: state.notes.clone(),
            recommendations: recommendations_for(state, log),
            probe_command,
        }
    }

    pub fn to_pretty_json(&self) -> Result<String, serde_json::Error> {
        serde_json::to_string_pretty(self)
    }

    pub fn to_pretty_text(&self) -> String {
        let mut text = String::new();
        let server_version = self.server_version.as_deref().unwrap_or("unknown");
        let server_state = if self.server_available {
            "reachable"
        } else {
            "unreachable"
        };
        let _ = writeln!(text, "Lesavka Diagnostics");
        let _ = writeln!(text, "client: v{}", self.client_version);
        let _ = writeln!(text, "server: {server_version} ({server_state})");
        let _ = writeln!(
            text,
            "session: routing={:?} view={:?} relay_active={} power={}",
            self.routing, self.view_mode, self.remote_active, self.power_state
        );
        let _ = writeln!(text, "source feed: {}", self.preview_source);
        let _ = writeln!(text, "breakout display: {}", self.breakout_display);
        let _ = writeln!(text);
        let _ = writeln!(text, "left eye");
        let _ = writeln!(text, "  surface: {}", self.left_surface);
        let _ = writeln!(text, "  capture: {}", self.left_capture_profile);
        let _ = writeln!(text, "  breakout: {}", self.left_breakout_profile);
        let _ = writeln!(text, "right eye");
        let _ = writeln!(text, "  surface: {}", self.right_surface);
        let _ = writeln!(text, "  capture: {}", self.right_capture_profile);
        let _ = writeln!(text, "  breakout: {}", self.right_breakout_profile);
        let _ = writeln!(text);
        let _ = writeln!(text, "device staging");
        let _ = writeln!(
            text,
            "  camera: {}",
            self.selected_camera.as_deref().unwrap_or("auto")
        );
        let _ = writeln!(
            text,
            "  microphone: {}",
            self.selected_microphone.as_deref().unwrap_or("auto")
        );
        let _ = writeln!(
            text,
            "  speaker: {}",
            self.selected_speaker.as_deref().unwrap_or("auto")
        );
        let _ = writeln!(
            text,
            "  keyboard: {}",
            self.selected_keyboard.as_deref().unwrap_or("all")
        );
        let _ = writeln!(
            text,
            "  mouse: {}",
            self.selected_mouse.as_deref().unwrap_or("all")
        );
        let _ = writeln!(text);
        let _ = writeln!(text, "launcher status");
        let _ = writeln!(text, "  {}", self.status);
        let _ = writeln!(text);
        let _ = writeln!(text, "recent samples");
        if self.recent_samples.is_empty() {
            let _ = writeln!(
                text,
                "  no live RTT/jitter/loss samples yet; this report is currently a launcher state snapshot."
            );
        } else {
            for sample in &self.recent_samples {
                let _ = writeln!(
                    text,
                    "  rtt={:.1}ms input={:.1}ms left={:.1}fps right={:.1}fps dropped={} queue={}",
                    sample.rtt_ms,
                    sample.input_latency_ms,
                    sample.left_fps,
                    sample.right_fps,
                    sample.dropped_frames,
                    sample.queue_depth
                );
            }
        }
        let _ = writeln!(text);
        let _ = writeln!(text, "recommendations");
        for item in &self.recommendations {
            let _ = writeln!(text, "  - {item}");
        }
        if !self.notes.is_empty() {
            let _ = writeln!(text);
            let _ = writeln!(text, "notes");
            for item in &self.notes {
                let _ = writeln!(text, "  - {item}");
            }
        }
        let _ = writeln!(text);
        let _ = writeln!(text, "quality probe");
        let _ = writeln!(text, "  {}", self.probe_command);
        text
    }
}

pub fn quality_probe_command() -> &'static str {
    "scripts/ci/hygiene_gate.sh && scripts/ci/quality_gate.sh"
}

fn recommendations_for(state: &LauncherState, log: &DiagnosticsLog) -> Vec<String> {
    let mut items = Vec::new();
    if !state.server_available {
        items.push(
            "The server is not reachable from this launcher yet, so stream-quality results would not be meaningful."
                .to_string(),
        );
    }
    if log.is_empty() {
        items.push(
            "Live RTT, jitter, packet-loss, and queue samples are the next diagnostics tranche; this panel currently reports launcher/session state."
                .to_string(),
        );
    }
    let heavy_capture = state.capture_sizes.iter().any(|preset| {
        matches!(
            preset,
            super::state::CaptureSizePreset::Source
                | super::state::CaptureSizePreset::P1080
                | super::state::CaptureSizePreset::P1440
        )
    });
    if heavy_capture {
        items.push(
            "If motion artifacting spikes, try a 900p or 720p capture profile before shrinking the breakout window; that usually lowers WAN pressure faster."
                .to_string(),
        );
    }
    if state.breakout_count() == 2 {
        items.push(
            "Both eye feeds are broken out right now. If the client starts struggling, compare in-launcher preview smoothness against full-window decode."
                .to_string(),
        );
    }
    if items.is_empty() {
        items.push("Session state looks stable. Collect a few real samples before changing capture settings.".to_string());
    }
    items
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::launcher::state::{DeviceSelection, LauncherState};

    fn sample(n: u64) -> PerformanceSample {
        PerformanceSample {
            rtt_ms: 20.0 + n as f32,
            input_latency_ms: 10.0 + n as f32,
            left_fps: 30.0,
            right_fps: 30.0,
            dropped_frames: n,
            queue_depth: n as u32,
        }
    }

    #[test]
    fn diagnostics_log_keeps_only_latest_samples_with_capacity() {
        let mut log = DiagnosticsLog::new(2);
        log.record(sample(1));
        log.record(sample(2));
        log.record(sample(3));

        let kept: Vec<u64> = log.iter().map(|item| item.dropped_frames).collect();
        assert_eq!(kept, vec![2, 3]);
        assert_eq!(log.latest().map(|s| s.dropped_frames), Some(3));
    }

    #[test]
    fn diagnostics_log_enforces_minimum_capacity() {
        let mut log = DiagnosticsLog::new(0);
        log.record(sample(1));
        log.record(sample(2));
        assert_eq!(log.len(), 1);
        assert_eq!(log.latest().map(|s| s.dropped_frames), Some(2));
    }

    #[test]
    fn snapshot_report_contains_state_fields_and_samples() {
        let mut state = LauncherState::new();
        state.devices = DeviceSelection {
            camera: Some("/dev/video0".to_string()),
            microphone: Some("alsa_input.usb".to_string()),
            speaker: Some("alsa_output.usb".to_string()),
            keyboard: Some("/dev/input/event10".to_string()),
            mouse: Some("/dev/input/event11".to_string()),
        };
        state.push_note("first note");

        let mut log = DiagnosticsLog::new(4);
        log.record(sample(7));

        let report = SnapshotReport::from_state(&state, &log, quality_probe_command().to_string());
        assert_eq!(report.selected_camera.as_deref(), Some("/dev/video0"));
        assert_eq!(
            report.selected_microphone.as_deref(),
            Some("alsa_input.usb")
        );
        assert_eq!(report.selected_speaker.as_deref(), Some("alsa_output.usb"));
        assert_eq!(
            report.selected_keyboard.as_deref(),
            Some("/dev/input/event10")
        );
        assert_eq!(report.selected_mouse.as_deref(), Some("/dev/input/event11"));
        assert_eq!(report.recent_samples.len(), 1);
        assert_eq!(report.notes, vec!["first note".to_string()]);
        assert!(report.status.contains("mode=remote"));
        assert!(report.client_version.starts_with("0."));
        assert!(report.left_capture_profile.contains("fps"));
    }

    #[test]
    fn snapshot_json_is_serializable_and_mentions_probe_command() {
        let report = SnapshotReport::from_state(
            &LauncherState::new(),
            &DiagnosticsLog::new(1),
            quality_probe_command().to_string(),
        );
        let json = report.to_pretty_json().expect("serialize");
        assert!(json.contains("quality_gate.sh"));
        assert!(json.contains("routing"));
        assert!(json.contains("view_mode"));
    }

    #[test]
    fn snapshot_text_mentions_versions_profiles_and_recommendations() {
        let report = SnapshotReport::from_state(
            &LauncherState::new(),
            &DiagnosticsLog::new(1),
            quality_probe_command().to_string(),
        );
        let text = report.to_pretty_text();
        assert!(text.contains("Lesavka Diagnostics"));
        assert!(text.contains("client: v"));
        assert!(text.contains("left eye"));
        assert!(text.contains("recommendations"));
    }

    #[test]
    fn quality_probe_command_mentions_both_gates() {
        let cmd = quality_probe_command();
        assert!(cmd.contains("hygiene_gate.sh"));
        assert!(cmd.contains("quality_gate.sh"));
    }
}