use serde::{Deserialize, Serialize};
use std::fs;
use std::path::Path;

use sal_os;
use sal_process;

/// Host dependency check error
#[derive(Debug)]
pub enum HostCheckError {
    Io(String),
}

impl std::fmt::Display for HostCheckError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            HostCheckError::Io(e) => write!(f, "IO error: {}", e),
        }
    }
}

impl std::error::Error for HostCheckError {}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct HostCheckReport {
    pub ok: bool,
    pub critical: Vec<String>,
    pub optional: Vec<String>,
    pub notes: Vec<String>,
}

fn hero_vm_root() -> String {
    let home = std::env::var("HOME").unwrap_or_else(|_| "/tmp".into());
    format!("{}/hero/virt/vms", home.trim_end_matches('/'))
}

fn bin_missing(name: &str) -> bool {
    sal_process::which(name).is_none()
}

/// Perform host dependency checks required for image preparation and Cloud Hypervisor run.
/// Returns a structured report that Rhai can consume easily.
pub fn host_check_deps() -> Result<HostCheckReport, HostCheckError> {
    let mut critical: Vec<String> = Vec::new();
    let mut optional: Vec<String> = Vec::new();
    let mut notes: Vec<String> = Vec::new();

    // Must run as root
    let uid_res = sal_process::run("id -u").silent(true).die(false).execute();
    match uid_res {
        Ok(r) if r.success => {
            let uid_s = r.stdout.trim();
            if uid_s != "0" {
                critical.push("not running as root (required for nbd/mount/network)".into());
            }
        }
        _ => {
            notes.push("failed to determine uid via `id -u`".into());
        }
    }

    // Core binaries required for CH and image manipulation
    let core_bins = [
        "cloud-hypervisor",        // CH binary (dynamic)
        "cloud-hypervisor-static", // CH static (if present)
        "ch-remote",
        "ch-remote-static",
        // hypervisor-fw is expected at /images/hypervisor-fw (not on PATH)
        "qemu-img",
        "qemu-nbd",
        "blkid",
        "tune2fs",
        "partprobe",
        "mount",
        "umount",
        "sed",
        "awk",
        "modprobe",
    ];

    // Networking helpers (for default bridge + NAT path)
    let net_bins = ["ip", "nft", "dnsmasq", "systemctl"];

    // Evaluate presence
    let mut have_any_ch = false;
    if !bin_missing("cloud-hypervisor") || !bin_missing("cloud-hypervisor-static") {
        have_any_ch = true;
    }
    if !have_any_ch {
        critical.push("cloud-hypervisor or cloud-hypervisor-static not found on PATH".into());
    }
    if bin_missing("ch-remote") && bin_missing("ch-remote-static") {
        critical.push("ch-remote or ch-remote-static not found on PATH".into());
    }

    for b in [&core_bins[4..], &net_bins[..]].concat() {
        if bin_missing(b) {
            // treat qemu/img/nbd stack and filesystem tools as critical
            // treat networking tools as critical too since default path provisions bridge/DHCP
            critical.push(format!("missing binary: {}", b));
        }
    }

    // Filesystem/path checks
    // Ensure /images exists and expected image files are present (ubuntu, alpine, hypervisor-fw)
    let images_root = "/images";
    if !Path::new(images_root).exists() {
        critical.push(format!("{} not found (expected base images directory)", images_root));
    } else {
        let ubuntu_path = format!("{}/noble-server-cloudimg-amd64.img", images_root);
        let alpine_path = format!("{}/alpine-virt-cloudimg-amd64.qcow2", images_root);
        let fw_path = format!("{}/hypervisor-fw", images_root);
        if !Path::new(&ubuntu_path).exists() {
            critical.push(format!("missing base image: {}", ubuntu_path));
        }
        if !Path::new(&alpine_path).exists() {
            critical.push(format!("missing base image: {}", alpine_path));
        }
        if !Path::new(&fw_path).exists() {
            critical.push(format!("missing firmware: {}", fw_path));
        }
    }

    // Ensure VM root directory is writable/creatable
    let vm_root = hero_vm_root();
    if let Err(e) = sal_os::mkdir(&vm_root) {
        critical.push(format!(
            "cannot create/access VM root directory {}: {}",
            vm_root, e
        ));
    } else {
        // also try writing a small file
        let probe_path = format!("{}/.__hero_probe", vm_root);
        if let Err(e) = fs::write(&probe_path, b"ok") {
            critical.push(format!(
                "VM root not writable {}: {}",
                vm_root, e
            ));
        } else {
            let _ = fs::remove_file(&probe_path);
        }
    }
 
    // Optional Mycelium IPv6 checks when enabled via env
    let ipv6_env = std::env::var("HERO_VIRT_IPV6_ENABLE").unwrap_or_else(|_| "".into());
    let ipv6_enabled = ipv6_env.eq_ignore_ascii_case("1") || ipv6_env.eq_ignore_ascii_case("true");
    if ipv6_enabled {
        // Require mycelium CLI
        if bin_missing("mycelium") {
            critical.push("mycelium CLI not found on PATH (required when HERO_VIRT_IPV6_ENABLE=true)".into());
        }
        // Validate interface presence and global IPv6
        let ifname = std::env::var("HERO_VIRT_MYCELIUM_IF").unwrap_or_else(|_| "mycelium".into());
        let check_if = sal_process::run(&format!("ip -6 addr show dev {}", ifname))
            .silent(true)
            .die(false)
            .execute();
        match check_if {
            Ok(r) if r.success => {
                let out = r.stdout;
                if !(out.contains("inet6") && out.contains("scope global")) {
                    notes.push(format!(
                        "iface '{}' present but no global IPv6 detected; Mycelium may not be up yet",
                        ifname
                    ));
                }
            }
            _ => {
                critical.push(format!(
                    "iface '{}' not found or no IPv6; ensure Mycelium is running",
                    ifname
                ));
            }
        }
        // Best-effort: parse `mycelium inspect` for Address
        let insp = sal_process::run("mycelium inspect").silent(true).die(false).execute();
        match insp {
            Ok(res) if res.success && res.stdout.contains("Address:") => {
                // good enough
            }
            _ => {
                notes.push("`mycelium inspect` did not return an Address; IPv6 overlay may be unavailable".into());
            }
        }
    }
 
    // Summarize ok flag
    let ok = critical.is_empty();
 
    Ok(HostCheckReport {
        ok,
        critical,
        optional,
        notes,
    })
}