//! `pixelpass doctor` — environment diagnostics.
//!
//! Screen-share failures are usually not pixelpass bugs but environment gaps:
//! a missing GStreamer plugin, an X vs. Wayland mismatch, or — the common one —
//! a GPU/driver with no working VA-API H.264 encoder, so the default
//! `vah264enc` pipeline never produces a byte and the viewer "can't connect."
//! `doctor` probes all of that up front and prints one actionable report, so a
//! remote tester can read it over a call instead of us guessing from logs. It
//! also validates any X11/Wayland test environment we stand up.
//!
//! Unlike [`crate::common::deps::check_host_binaries`], which bails on the first
//! missing dependency, doctor runs *every* check and reports them together — a
//! diagnostic wants the whole picture, not the first failure.

use anyhow::Result;
use std::time::Duration;

use crate::common::deps;
use crate::common::display::DisplayServer;
use crate::common::endpoint;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Status {
    /// Working as needed.
    Ok,
    /// Degraded but not fatal (e.g. a fallback path is available).
    Warn,
    /// Screen-sharing will not work until this is fixed.
    Fail,
    /// Neutral fact, no judgement.
    Info,
}

impl Status {
    fn icon(self) -> char {
        match self {
            Self::Ok => '✓',
            Self::Warn => '!',
            Self::Fail => '✗',
            Self::Info => '·',
        }
    }
}

/// One line in the report: a status, a short label, a detail, and an optional
/// remediation hint printed on its own indented line.
pub struct Check {
    pub status: Status,
    pub label: String,
    pub detail: String,
    pub hint: Option<String>,
}

impl Check {
    fn new(status: Status, label: impl Into<String>, detail: impl Into<String>) -> Self {
        Self {
            status,
            label: label.into(),
            detail: detail.into(),
            hint: None,
        }
    }

    fn ok(label: impl Into<String>, detail: impl Into<String>) -> Self {
        Self::new(Status::Ok, label, detail)
    }
    fn warn(label: impl Into<String>, detail: impl Into<String>) -> Self {
        Self::new(Status::Warn, label, detail)
    }
    fn fail(label: impl Into<String>, detail: impl Into<String>) -> Self {
        Self::new(Status::Fail, label, detail)
    }
    fn info(label: impl Into<String>, detail: impl Into<String>) -> Self {
        Self::new(Status::Info, label, detail)
    }

    fn with_hint(mut self, hint: impl Into<String>) -> Self {
        self.hint = Some(hint.into());
        self
    }
}

/// Tally of the non-trivial statuses across every section.
#[derive(Debug, Default, Clone, Copy, PartialEq, Eq)]
pub struct Summary {
    pub fails: usize,
    pub warns: usize,
}

/// A named group of checks, printed under a header.
struct Section {
    name: &'static str,
    checks: Vec<Check>,
}

/// Run all diagnostics and print the report. Always prints; the process exit
/// code is non-zero only when a hard failure (a `Fail`) was found, so scripts
/// and CI can gate on it while a human still sees everything.
pub async fn run(relay: Option<String>) -> Result<()> {
    let display = DisplayServer::detect();

    let sections = vec![
        system_section(display),
        capture_section(display),
        encode_section(),
        mux_audio_section(),
        viewer_section(),
        network_section(relay.as_deref()).await,
    ];

    print_report(&sections);

    let summary = summarize(sections.iter().flat_map(|s| s.checks.iter()));
    print_summary(summary, &sections);

    if summary.fails > 0 {
        std::process::exit(1);
    }
    Ok(())
}

// ── sections ──────────────────────────────────────────────────────────────

fn system_section(display: DisplayServer) -> Section {
    let mut checks = vec![
        Check::info(
            "pixelpass",
            format!("{} (gui: {})", env!("CARGO_PKG_VERSION"), gui_built()),
        ),
        Check::info("distro", distro_detail()),
        display_check(display),
    ];

    // Probe the actual X server when one is reachable — this is where an xlibre
    // vs. Xorg difference (the thing we most want to see on a tester's box)
    // shows up. Skip it on a pure Wayland session with no X at all.
    if display == DisplayServer::X11 || std::env::var_os("DISPLAY").is_some() {
        checks.push(x_server_check());
    }

    Section {
        name: "System",
        checks,
    }
}

fn capture_section(display: DisplayServer) -> Section {
    let mut checks = vec![
        bin_check("gst-launch-1.0", "gstreamer tools"),
        bin_check("gst-inspect-1.0", "gstreamer tools"),
    ];

    match display {
        DisplayServer::Wayland => {
            checks.push(gst_check("pipewiresrc", "Wayland capture"));
        }
        DisplayServer::X11 => {
            checks.push(gst_check("ximagesrc", "X11 capture"));
            checks.push(match deps::which("xwininfo") {
                Some(p) => Check::ok("window picker", p.display().to_string())
                    .with_hint("needed only for `--window` (share a single window)"),
                None => Check::info("window picker", "xwininfo not found")
                    .with_hint("optional — only `--window` needs it"),
            });
        }
        DisplayServer::Unknown => {
            checks.push(
                Check::info("capture backend", "unknown — cannot probe a source element")
                    .with_hint("force one with `--display-server x11|wayland` when hosting"),
            );
        }
    }

    Section {
        name: "Capture (host)",
        checks,
    }
}

fn encode_section() -> Section {
    Section {
        name: "Encode",
        checks: vec![hardware_encode_check(), software_encode_check()],
    }
}

/// The load-bearing check for the common "viewer can't connect" report: the
/// default host pipeline uses `vah264enc`, which needs both the GStreamer VA
/// plugin *and* a GPU/driver that actually exposes an H.264 encode entrypoint.
/// A box with the plugin but no encode entrypoint (or no render node) produces
/// no video — the exact silent failure `--no-hwencode` works around.
fn hardware_encode_check() -> Check {
    if !deps::gst_element_exists("vah264enc") {
        return Check::warn("hardware H.264", "vah264enc plugin not installed").with_hint(format!(
            "{} — or just host with `--no-hwencode` (software x264)",
            deps::install_hint_for_gst_element("vah264enc")
        ));
    }

    if !has_render_node() {
        return Check::warn(
            "hardware H.264",
            "vah264enc present, but no DRM render node (/dev/dri/renderD*)",
        )
        .with_hint("GPU encode is unavailable here — host with `--no-hwencode`");
    }

    match vainfo_output() {
        Some(out) if vainfo_has_h264_encode(&out) => Check::ok(
            "hardware H.264",
            "VA-API H.264 encode available (vah264enc)",
        ),
        Some(_) => Check::warn(
            "hardware H.264",
            "vah264enc present, but VA-API reports no H.264 encode entrypoint",
        )
        .with_hint("this GPU/driver can't hardware-encode H.264 — host with `--no-hwencode`"),
        None => Check::info(
            "hardware H.264",
            "vah264enc + render node present; couldn't confirm the VA-API encode entrypoint",
        )
        .with_hint("install `vainfo` (libva-utils) to verify, or just test a real host session"),
    }
}

fn software_encode_check() -> Check {
    if deps::gst_element_exists("x264enc") {
        Check::ok("software H.264", "x264enc available (`--no-hwencode`)")
    } else {
        Check::warn("software H.264", "x264enc not installed").with_hint(format!(
            "{} — the fallback for GPUs without VA-API H.264 encode",
            deps::install_hint_for_gst_element("x264enc")
        ))
    }
}

fn mux_audio_section() -> Section {
    // These live in plugins-bad/-good/-libav and plugins-base; all are required
    // for either backend, so a miss here is a hard Fail.
    let tail = [
        "h264parse",
        "mpegtsmux",
        "aacparse",
        "avenc_aac",
        "pulsesrc",
        "videoscale",
    ];
    let missing: Vec<&str> = tail
        .iter()
        .copied()
        .filter(|e| !deps::gst_element_exists(e))
        .collect();

    let tail_check = if missing.is_empty() {
        Check::ok("mux + audio tail", tail.join(", "))
    } else {
        Check::fail(
            "mux + audio tail",
            format!("missing: {}", missing.join(", ")),
        )
        .with_hint(deps::install_hint_for_gst_element(missing[0]))
    };

    Section {
        name: "Mux / audio",
        checks: vec![tail_check, bin_check("pactl", "pactl")],
    }
}

fn viewer_section() -> Section {
    let mpv = deps::which("mpv");
    let vlc = deps::which("vlc");

    let check = match (mpv, vlc) {
        (Some(p), _) => Check::ok("player", format!("mpv ({})", p.display())),
        (None, Some(p)) => Check::ok("player", format!("vlc ({})", p.display()))
            .with_hint("mpv is the recommended player; vlc needs the dvb + ffmpeg plugins"),
        (None, None) => Check::warn("player", "neither mpv nor vlc found")
            .with_hint("a viewer needs one of them; the GUI launches mpv by default"),
    };

    Section {
        name: "Viewer",
        checks: vec![check],
    }
}

/// Bind a real video-plane endpoint and wait briefly for a relay, mirroring
/// what a host does. Directly relevant to "couldn't connect": if this machine
/// can't reach a relay, hole-punching to a peer is unlikely to work either.
async fn network_section(relay: Option<&str>) -> Section {
    let check = match endpoint::bind(relay).await {
        Ok(ep) => {
            let online = tokio::time::timeout(Duration::from_secs(8), ep.online())
                .await
                .is_ok();
            let relay_count = ep.addr().addrs.iter().filter(|a| a.is_relay()).count();
            let where_ = relay.map(|r| format!(" ({r})")).unwrap_or_default();
            // Close gracefully so iroh doesn't log a scary "Endpoint dropped
            // without calling close" error into the middle of the report.
            ep.close().await;

            if online && relay_count > 0 {
                Check::ok("relay", format!("home relay reachable{where_}"))
            } else if online {
                Check::warn(
                    "relay",
                    format!("endpoint online but no relay address{where_}"),
                )
                .with_hint(
                    "n0 DNS discovery may still connect peers, but relay fallback is degraded",
                )
            } else {
                Check::warn("relay", format!("no relay connected within 8s{where_}")).with_hint(
                    "check connectivity/firewall; peers behind NAT rely on the relay to rendezvous",
                )
            }
        }
        Err(e) => Check::fail("relay", format!("could not bind endpoint: {e}")),
    };

    Section {
        name: "Network",
        checks: vec![check],
    }
}

// ── small check builders ────────────────────────────────────────────────────

fn bin_check(bin: &str, label: &str) -> Check {
    match deps::which(bin) {
        Some(p) => Check::ok(label, format!("{bin} ({})", p.display())),
        None => Check::fail(label, format!("{bin} not found on PATH"))
            .with_hint(deps::install_hint_for_bin(bin)),
    }
}

fn gst_check(element: &str, label: &str) -> Check {
    if deps::gst_element_exists(element) {
        Check::ok(label, element.to_string())
    } else {
        Check::fail(
            label,
            format!("GStreamer element `{element}` not available"),
        )
        .with_hint(deps::install_hint_for_gst_element(element))
    }
}

fn display_check(display: DisplayServer) -> Check {
    let env = display_env_summary();
    match display {
        DisplayServer::Wayland => Check::ok("display server", format!("Wayland ({env})")),
        DisplayServer::X11 => Check::ok("display server", format!("X11 ({env})")),
        DisplayServer::Unknown => Check::fail("display server", format!("undetected ({env})"))
            .with_hint(
                "no WAYLAND_DISPLAY/DISPLAY/XDG_SESSION_TYPE — capture can't start; \
                 run inside a graphical session or pass `--display-server`",
            ),
    }
}

/// Connect to the X server and report its vendor + version. This is how an
/// xlibre server distinguishes itself from stock Xorg (vendor string / release
/// number), which is exactly what we want to see on a tester's machine.
fn x_server_check() -> Check {
    use x11rb::connection::Connection;
    match x11rb::connect(None) {
        Ok((conn, _screen)) => {
            let setup = conn.setup();
            let vendor = String::from_utf8_lossy(&setup.vendor);
            let detail = format!(
                "vendor \"{}\", protocol {}.{}, release {}",
                vendor.trim(),
                setup.protocol_major_version,
                setup.protocol_minor_version,
                setup.release_number,
            );
            let label = "X server";
            if vendor.to_lowercase().contains("xlibre") {
                Check::info(label, format!("XLibre — {detail}"))
            } else {
                Check::info(label, detail)
            }
        }
        Err(_) => Check::info("X server", "DISPLAY set but the X server is unreachable"),
    }
}

// ── environment helpers ─────────────────────────────────────────────────────

fn gui_built() -> &'static str {
    if cfg!(feature = "gui") { "yes" } else { "no" }
}

fn distro_detail() -> String {
    let id = deps::detect_distro();
    let pretty = os_release_field("PRETTY_NAME");
    match (id, pretty) {
        (Some(id), Some(p)) => format!("{id} ({p})"),
        (Some(id), None) => id,
        (None, Some(p)) => p,
        (None, None) => "unknown".to_string(),
    }
}

fn os_release_field(key: &str) -> Option<String> {
    let contents = std::fs::read_to_string("/etc/os-release").ok()?;
    for line in contents.lines() {
        if let Some(rest) = line.strip_prefix(&format!("{key}=")) {
            return Some(rest.trim_matches('"').to_string());
        }
    }
    None
}

fn display_env_summary() -> String {
    let mut parts = Vec::new();
    for var in [
        "WAYLAND_DISPLAY",
        "DISPLAY",
        "XDG_SESSION_TYPE",
        "XDG_CURRENT_DESKTOP",
    ] {
        if let Some(v) = std::env::var_os(var) {
            parts.push(format!("{var}={}", v.to_string_lossy()));
        }
    }
    if parts.is_empty() {
        "no display env vars set".to_string()
    } else {
        parts.join(", ")
    }
}

fn has_render_node() -> bool {
    let Ok(entries) = std::fs::read_dir("/dev/dri") else {
        return false;
    };
    entries
        .flatten()
        .any(|e| e.file_name().to_string_lossy().starts_with("renderD"))
}

fn vainfo_output() -> Option<String> {
    deps::which("vainfo")?;
    let out = std::process::Command::new("vainfo").output().ok()?;
    // vainfo prints its profile/entrypoint table to stdout; some builds also
    // spill driver banners to stderr. Concatenate both so parsing is robust.
    let mut s = String::from_utf8_lossy(&out.stdout).into_owned();
    s.push_str(&String::from_utf8_lossy(&out.stderr));
    Some(s)
}

/// Pure: does a `vainfo` dump advertise an H.264 *encode* entrypoint? vainfo
/// lists one `VAProfile… : VAEntrypoint…` pair per line; hardware H.264 encode
/// is any `VAProfileH264*` profile paired with an `EncSlice`/`EncSliceLP`
/// entrypoint. VLD-only H.264 (decode) does not count.
fn vainfo_has_h264_encode(output: &str) -> bool {
    output.lines().any(|line| {
        line.contains("VAProfileH264")
            && (line.contains("VAEntrypointEncSlice") || line.contains("VAEntrypointEncSliceLP"))
    })
}

// ── reporting ───────────────────────────────────────────────────────────────

fn print_report(sections: &[Section]) {
    println!("pixelpass doctor\n");
    for section in sections {
        println!("{}", section.name);
        for check in &section.checks {
            println!(
                "  {} {:<16}  {}",
                check.status.icon(),
                check.label,
                check.detail
            );
            if let Some(hint) = &check.hint {
                println!("        → {hint}");
            }
        }
        println!();
    }
}

fn summarize<'a>(checks: impl Iterator<Item = &'a Check>) -> Summary {
    let mut summary = Summary::default();
    for check in checks {
        match check.status {
            Status::Fail => summary.fails += 1,
            Status::Warn => summary.warns += 1,
            Status::Ok | Status::Info => {}
        }
    }
    summary
}

fn print_summary(summary: Summary, sections: &[Section]) {
    let hosting = hosting_verdict(sections);
    let counts = match (summary.fails, summary.warns) {
        (0, 0) => "all checks passed".to_string(),
        (0, w) => format!("{w} warning{}", plural(w)),
        (f, 0) => format!("{f} failure{}", plural(f)),
        (f, w) => format!("{f} failure{}, {w} warning{}", plural(f), plural(w)),
    };
    println!("Summary: {counts}. {hosting}");
}

fn plural(n: usize) -> &'static str {
    if n == 1 { "" } else { "s" }
}

/// A one-line verdict on whether this box can host, and how. Reads the actual
/// encode + capture checks rather than the raw tally so the advice is specific.
fn hosting_verdict(sections: &[Section]) -> String {
    let find = |section: &str, label: &str| -> Option<Status> {
        sections
            .iter()
            .find(|s| s.name == section)?
            .checks
            .iter()
            .find(|c| c.label == label)
            .map(|c| c.status)
    };

    let hw = find("Encode", "hardware H.264");
    let sw_ok = find("Encode", "software H.264") == Some(Status::Ok);
    let capture_broken = sections
        .iter()
        .find(|s| s.name == "Capture (host)")
        .map(|s| s.checks.iter().any(|c| c.status == Status::Fail))
        .unwrap_or(false);

    if capture_broken {
        "Hosting will fail: the capture backend is incomplete (see Capture above).".to_string()
    } else if hw == Some(Status::Ok) {
        "Hosting will work (hardware H.264 encode).".to_string()
    } else if hw == Some(Status::Info) && sw_ok {
        // Plugin + render node present but VA-API unverified (no vainfo): the
        // default encoder is likely fine; `--no-hwencode` is the safe fallback.
        "Hosting should work (hardware H.264 likely; `--no-hwencode` is the fallback).".to_string()
    } else if sw_ok {
        "Hosting should work with `--no-hwencode` (software H.264 encode).".to_string()
    } else {
        "Hosting may fail: no working H.264 encoder found (see Encode above).".to_string()
    }
}

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

    #[test]
    fn vainfo_detects_h264_encode_entrypoint() {
        // Realistic AMD/RADV-style dump: H.264 has both decode (VLD) and encode.
        let dump = "\
      VAProfileH264Main               : VAEntrypointVLD
      VAProfileH264Main               : VAEntrypointEncSlice
      VAProfileH264High               : VAEntrypointVLD
      VAProfileHEVCMain               : VAEntrypointEncSlice";
        assert!(vainfo_has_h264_encode(dump));
    }

    #[test]
    fn vainfo_low_power_encode_counts() {
        let dump = "VAProfileH264ConstrainedBaseline: VAEntrypointEncSliceLP";
        assert!(vainfo_has_h264_encode(dump));
    }

    #[test]
    fn vainfo_decode_only_h264_is_not_encode() {
        // Decode-only H.264 (VLD) plus HEVC encode must NOT be read as H.264
        // encode — this is exactly the "default encoder fails" case.
        let dump = "\
      VAProfileH264Main               : VAEntrypointVLD
      VAProfileH264High               : VAEntrypointVLD
      VAProfileHEVCMain               : VAEntrypointEncSlice";
        assert!(!vainfo_has_h264_encode(dump));
    }

    #[test]
    fn vainfo_empty_is_not_encode() {
        assert!(!vainfo_has_h264_encode(""));
    }

    #[test]
    fn summarize_counts_fails_and_warns_only() {
        let checks = [
            Check::ok("a", "x"),
            Check::info("b", "x"),
            Check::warn("c", "x"),
            Check::warn("d", "x"),
            Check::fail("e", "x"),
        ];
        let summary = summarize(checks.iter());
        assert_eq!(summary, Summary { fails: 1, warns: 2 });
    }

    #[test]
    fn hosting_verdict_prefers_hardware_then_software() {
        let hw = vec![Section {
            name: "Encode",
            checks: vec![
                Check::ok("hardware H.264", "ok"),
                Check::ok("software H.264", "ok"),
            ],
        }];
        assert!(hosting_verdict(&hw).contains("hardware"));

        let sw = vec![Section {
            name: "Encode",
            checks: vec![
                Check::warn("hardware H.264", "no"),
                Check::ok("software H.264", "ok"),
            ],
        }];
        assert!(sw_verdict_uses_no_hwencode(&hosting_verdict(&sw)));

        let none = vec![Section {
            name: "Encode",
            checks: vec![
                Check::warn("hardware H.264", "no"),
                Check::warn("software H.264", "no"),
            ],
        }];
        assert!(hosting_verdict(&none).contains("may fail"));
    }

    fn sw_verdict_uses_no_hwencode(v: &str) -> bool {
        v.contains("--no-hwencode")
    }

    #[test]
    fn capture_failure_dominates_verdict() {
        let sections = vec![
            Section {
                name: "Capture (host)",
                checks: vec![Check::fail("X11 capture", "missing")],
            },
            Section {
                name: "Encode",
                checks: vec![Check::ok("hardware H.264", "ok")],
            },
        ];
        assert!(hosting_verdict(&sections).contains("capture"));
    }
}