use anyhow::{Result, bail};
use std::path::PathBuf;
use std::process::Command;

use crate::cli::HostOpts;
use crate::common::display::DisplayServer;

pub fn check_host_binaries(display: DisplayServer, opts: &HostOpts) -> Result<()> {
    // Unknown is handled (and rejected) by the caller; nothing to check here.
    if display == DisplayServer::Unknown {
        return Ok(());
    }

    // Shared across both backends: the gst tools, audio routing, and the
    // encode/mux tail elements.
    require("gst-launch-1.0")?;
    require("gst-inspect-1.0")?;
    require("pactl")?;
    require_gst_element("h264parse")?;
    require_gst_element("mpegtsmux")?;
    require_gst_element("pulsesrc")?;
    require_gst_element("avenc_aac")?;
    require_gst_element("aacparse")?;

    // Encoder depends on --no-hwencode (software x264 vs hardware VAAPI).
    if opts.no_hwencode {
        require_gst_element("x264enc")?;
    } else {
        require_gst_element("vah264enc")?;
    }

    // Per-backend video source, plus the X11 window-picker when --window is set.
    match display {
        DisplayServer::Wayland => require_gst_element("pipewiresrc")?,
        DisplayServer::X11 => {
            require_gst_element("ximagesrc")?;
            if opts.window {
                require("xwininfo")?;
            }
        }
        DisplayServer::Unknown => unreachable!("early-returned above"),
    }

    Ok(())
}

fn require(bin: &str) -> Result<PathBuf> {
    match which(bin) {
        Some(p) => Ok(p),
        None => bail!("`{bin}` not found on PATH.\n{}", install_hint_for_bin(bin)),
    }
}

fn require_gst_element(name: &str) -> Result<()> {
    let ok = Command::new("gst-inspect-1.0")
        .args(["--exists", name])
        .status()
        .map(|s| s.success())
        .unwrap_or(false);
    if !ok {
        bail!(
            "GStreamer element `{name}` not available.\n{}",
            install_hint_for_gst_element(name)
        );
    }
    Ok(())
}

fn which(bin: &str) -> Option<PathBuf> {
    let path = std::env::var_os("PATH")?;
    for dir in std::env::split_paths(&path) {
        let candidate = dir.join(bin);
        if candidate.is_file() {
            return Some(candidate);
        }
    }
    None
}

fn install_hint_for_bin(bin: &str) -> String {
    let distro = detect_distro();
    let pkg = match bin {
        "gst-launch-1.0" | "gst-inspect-1.0" => match distro.as_deref() {
            Some("arch" | "cachyos" | "manjaro" | "endeavouros") => "gstreamer gst-plugins-base",
            Some("debian" | "ubuntu" | "pop" | "linuxmint") => "gstreamer1.0-tools",
            Some("fedora" | "nobara") => "gstreamer1 gstreamer1-plugins-base-tools",
            _ => "gstreamer + tools",
        },
        "pactl" => match distro.as_deref() {
            Some("arch" | "cachyos" | "manjaro" | "endeavouros") => "libpulse",
            Some("debian" | "ubuntu" | "pop" | "linuxmint") => "pulseaudio-utils",
            Some("fedora" | "nobara") => "pulseaudio-utils",
            Some("opensuse" | "opensuse-tumbleweed" | "opensuse-leap") => "pulseaudio-utils",
            _ => "pulseaudio-utils (provides `pactl`)",
        },
        "xwininfo" => match distro.as_deref() {
            Some("arch" | "cachyos" | "manjaro" | "endeavouros") => "xorg-xwininfo",
            Some("debian" | "ubuntu" | "pop" | "linuxmint") => "x11-utils",
            Some("fedora" | "nobara") => "xorg-x11-utils",
            Some("opensuse" | "opensuse-tumbleweed" | "opensuse-leap") => "xwininfo",
            _ => "xwininfo (X11 window-info utility)",
        },
        _ => bin,
    };
    install_command(&distro, pkg)
}

fn install_hint_for_gst_element(name: &str) -> String {
    let distro = detect_distro();
    let pkg = match name {
        "pipewiresrc" => match distro.as_deref() {
            Some("arch" | "cachyos" | "manjaro" | "endeavouros") => "gst-plugin-pipewire",
            Some("debian" | "ubuntu" | "pop" | "linuxmint") => "gstreamer1.0-pipewire",
            Some("fedora" | "nobara") => "pipewire-gstreamer",
            Some("opensuse" | "opensuse-tumbleweed" | "opensuse-leap") => "pipewire-gstreamer",
            _ => "the GStreamer PipeWire plugin",
        },
        "vah264enc" => match distro.as_deref() {
            Some("arch" | "cachyos" | "manjaro" | "endeavouros") => "gst-plugin-va",
            Some("debian" | "ubuntu" | "pop" | "linuxmint") => "gstreamer1.0-plugins-bad",
            Some("fedora" | "nobara") => "gstreamer1-plugins-bad-free",
            Some("opensuse" | "opensuse-tumbleweed" | "opensuse-leap") => "gstreamer-plugins-bad",
            _ => "the GStreamer VA-API plugin (requires an H.264-capable GPU; almost all modern GPUs)",
        },
        "x264enc" => match distro.as_deref() {
            Some("arch" | "cachyos" | "manjaro" | "endeavouros") => "gst-plugins-ugly",
            Some("debian" | "ubuntu" | "pop" | "linuxmint") => "gstreamer1.0-plugins-ugly",
            Some("fedora" | "nobara") => "gstreamer1-plugins-ugly",
            Some("opensuse" | "opensuse-tumbleweed" | "opensuse-leap") => "gstreamer-plugins-ugly",
            _ => "the GStreamer x264 plugin (plugins-ugly)",
        },
        "ximagesrc" => match distro.as_deref() {
            Some("arch" | "cachyos" | "manjaro" | "endeavouros") => "gst-plugins-good",
            Some("debian" | "ubuntu" | "pop" | "linuxmint") => "gstreamer1.0-plugins-good",
            Some("fedora" | "nobara") => "gstreamer1-plugins-good",
            Some("opensuse" | "opensuse-tumbleweed" | "opensuse-leap") => "gstreamer-plugins-good",
            _ => "the GStreamer X11 plugin (plugins-good)",
        },
        "h264parse" | "mpegtsmux" | "aacparse" => match distro.as_deref() {
            Some("arch" | "cachyos" | "manjaro" | "endeavouros") => "gst-plugins-bad",
            Some("debian" | "ubuntu" | "pop" | "linuxmint") => "gstreamer1.0-plugins-bad",
            Some("fedora" | "nobara") => "gstreamer1-plugins-bad-free",
            Some("opensuse" | "opensuse-tumbleweed" | "opensuse-leap") => "gstreamer-plugins-bad",
            _ => "the GStreamer plugins-bad set",
        },
        "pulsesrc" => match distro.as_deref() {
            Some("arch" | "cachyos" | "manjaro" | "endeavouros") => "gst-plugins-good",
            Some("debian" | "ubuntu" | "pop" | "linuxmint") => "gstreamer1.0-pulseaudio",
            Some("fedora" | "nobara") => "gstreamer1-plugins-good",
            Some("opensuse" | "opensuse-tumbleweed" | "opensuse-leap") => "gstreamer-plugins-good",
            _ => "the GStreamer PulseAudio plugin",
        },
        "avenc_aac" => match distro.as_deref() {
            Some("arch" | "cachyos" | "manjaro" | "endeavouros") => "gst-libav",
            Some("debian" | "ubuntu" | "pop" | "linuxmint") => "gstreamer1.0-libav",
            Some("fedora" | "nobara") => "gstreamer1-libav",
            Some("opensuse" | "opensuse-tumbleweed" | "opensuse-leap") => "gstreamer-libav",
            _ => "the GStreamer libav (avenc) plugin",
        },
        _ => name,
    };
    install_command(&distro, pkg)
}

fn install_command(distro: &Option<String>, pkg: &str) -> String {
    let cmd = match distro.as_deref() {
        Some("arch" | "cachyos" | "manjaro" | "endeavouros") => format!("sudo pacman -S {pkg}"),
        Some("debian" | "ubuntu" | "pop" | "linuxmint") => format!("sudo apt install {pkg}"),
        Some("fedora" | "nobara") => format!("sudo dnf install {pkg}"),
        Some("opensuse" | "opensuse-tumbleweed" | "opensuse-leap") => format!("sudo zypper install {pkg}"),
        _ => format!("install the `{pkg}` package via your distro's package manager"),
    };
    format!("Install hint: {cmd}")
}

fn detect_distro() -> 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("ID=") {
            return Some(rest.trim_matches('"').to_lowercase());
        }
    }
    None
}