use {
    derive_more::Display,
    error_stack::{bail, report, Context, IntoReport, Result, ResultExt},
    fatfs::{FileSystem, FormatVolumeOptions, FsOptions, ReadWriteSeek},
    std::{fmt::Display, fs::File, io, path::Path, process::Command},
};

fn main() -> Result<(), Error> {
    let mut args = std::env::args();
    args.next();

    // let disk_meta = fs::metadata("target/disk.img").unwrap();
    // let config_meta = fs::metadata("system.toml").unwrap();

    // if disk_meta.modified().unwrap() < config_meta.modified().unwrap() {
    //     // TODO: work on adding in system.toml support
    //     // TODO: rebuild the disk
    // }

    match args.next().as_deref() {
        Some("build" | "b") => {
            let mut release = false;
            let mut target = Target::X86_64;
            for arg in args {
                if arg == "-r" || arg == "--release" {
                    release = true;
                } else if arg == "rv64" || arg == "riscv64" || arg == "riscv64-virt" {
                    target = Target::Riscv64Virt;
                } else if arg == "arm64" || arg == "aarch64" || arg == "aarch64-virt" {
                    target = Target::Aarch64;
                } else {
                    return Err(report!(Error::InvalidSubCom));
                }
            }

            build(release, target).change_context(Error::Build)
        }
        Some("run" | "r") => {
            let mut release = false;
            let mut target = Target::X86_64;
            for arg in args {
                if arg == "-r" || arg == "--release" {
                    release = true;
                } else if arg == "rv64" || arg == "riscv64" || arg == "riscv64-virt" {
                    target = Target::Riscv64Virt;
                } else if arg == "arm64" || arg == "aarch64" || arg == "aarch64-virt" {
                    target = Target::Aarch64;
                } else {
                    return Err(report!(Error::InvalidSubCom));
                }
            }

            build(release, target)?;
            run(release, target)
        }
        Some("help" | "h") => {
            println!(concat!(
                "AbleOS RepBuild\n",
                "Subcommands:\n",
                "  build (b): Build a bootable disk image\n",
                "   help (h): Print this message\n",
                "    run (r): Build and run AbleOS in QEMU\n\n",
                "Options for build and run:\n",
                "        -r: build in release mode",
                "  [target]: sets target"
            ),);
            Ok(())
        }
        _ => Err(report!(Error::InvalidSubCom)),
    }
}

fn get_fs() -> Result<FileSystem<impl ReadWriteSeek>, io::Error> {
    let mut img = File::options()
        .read(true)
        .write(true)
        .create(true)
        .open(Path::new("target/disk.img"))?;

    img.set_len(1024 * 1024 * 64)?;

    fatfs::format_volume(&mut img, FormatVolumeOptions::new())?;

    let fs = FileSystem::new(img, FsOptions::new())?;
    let bootdir = fs.root_dir().create_dir("efi")?.create_dir("boot")?;

    io::copy(
        &mut File::open("limine/BOOTX64.EFI")
            .into_report()
            .attach_printable("copying Limine bootloader (have you pulled the submodule?)")?,
        &mut bootdir.create_file("bootx64.efi")?,
    )?;

    io::copy(
        &mut File::open("limine/BOOTAA64.EFI")
            .into_report()
            .attach_printable(
                "copying Limine bootloader arm version (have you pulled the submodule?)",
            )?,
        &mut bootdir.create_file("bootaa64.efi")?,
    )?;

    io::copy(
        &mut File::open("repbuild/limine.cfg")?,
        &mut fs.root_dir().create_file("limine.cfg")?,
    )?;

    io::copy(
        &mut File::open("repbuild/background.bmp")?,
        &mut fs.root_dir().create_file("background.bmp")?,
    )?;
    io::copy(
        &mut File::open("repbuild/holeybytes/inf_loop.hb")?,
        &mut fs.root_dir().create_file("inf_loop.hb")?,
    )?;

    io::copy(
        &mut File::open("repbuild/holeybytes/ecall.hb")?,
        &mut fs.root_dir().create_file("ecall.hb")?,
    )?;

    drop(bootdir);
    Ok(fs)
}

fn build(release: bool, target: Target) -> Result<(), Error> {
    let fs = get_fs().change_context(Error::Io)?;
    let mut com = Command::new("cargo");
    com.current_dir("kernel");
    com.args(["b"]);
    if release {
        com.arg("-r");
    }

    if target == Target::Riscv64Virt {
        com.args(["--target", "targets/riscv64-virt-ableos.json"]);
    }
    if target == Target::Aarch64 {
        com.args(["--target", "targets/aarch64-virt-ableos.json"]);
    }

    match com.status() {
        Ok(s) if s.code() != Some(0) => bail!(Error::Build),
        Err(e) => bail!(report!(e).change_context(Error::Build)),
        _ => (),
    }

    let kernel_dir = match target {
        Target::X86_64 => "target/x86_64-ableos",
        Target::Riscv64Virt => "target/riscv64-virt-ableos",
        Target::Aarch64 => "target/aarch64-virt-ableos",
    };

    (|| -> std::io::Result<_> {
        io::copy(
            &mut File::open(
                Path::new(kernel_dir)
                    .join(if release { "release" } else { "debug" })
                    .join("kernel"),
            )?,
            &mut fs.root_dir().create_file("kernel")?,
        )
        .map(|_| ())
    })()
    .into_report()
    .change_context(Error::Io)
}

fn run(release: bool, target: Target) -> Result<(), Error> {
    let mut com = match target {
        Target::X86_64 => Command::new("qemu-system-x86_64"),
        Target::Riscv64Virt => Command::new("qemu-system-riscv64"),
        Target::Aarch64 => Command::new("qemu-system-aarch64"),
    };
    let ovmf_path = fetch_ovmf(target);

    match target {
        Target::X86_64 => {
            #[rustfmt::skip]
            com.args([
                "-bios", &ovmf_path.change_context(Error::OvmfFetch)?,
                "-drive", "file=target/disk.img,format=raw",
                "-m", "4G",
                "-smp", "cores=4",
            ]);
        }
        Target::Riscv64Virt => {
            #[rustfmt::skip]
            com.args([
                "-M", "virt",
                "-m", "128M",
                "-serial", "stdio",
                "-kernel",
                if release {
                    "target/riscv64-virt-ableos/release/kernel"
                } else {
                    "target/riscv64-virt-ableos/debug/kernel"
                }
            ]);
        }
        Target::Aarch64 => {
            #[rustfmt::skip]
            com.args([
                "-M", "virt",
                "-cpu", "cortex-a72",
                "-device", "ramfb",
                "-device", "qemu-xhci",
                "-device", "usb-kbd",
                "-m", "2G",
                "-bios", &ovmf_path.change_context(Error::OvmfFetch)?,
                "-drive", "file=target/disk.img,format=raw",
            ]);
        }
    }

    match com
        .status()
        .into_report()
        .change_context(Error::ProcessSpawn)?
    {
        s if s.success() => Ok(()),
        s => Err(report!(Error::Qemu(s.code()))),
    }
}

fn fetch_ovmf(target: Target) -> Result<String, OvmfFetchError> {
    let (ovmf_url, ovmf_path) = match target {
        Target::X86_64 => (
            "https://retrage.github.io/edk2-nightly/bin/RELEASEX64_OVMF.fd",
            "target/RELEASEX64_OVMF.fd",
        ),
        Target::Riscv64Virt => return Err(OvmfFetchError::Empty.into()),
        Target::Aarch64 => (
            "https://retrage.github.io/edk2-nightly/bin/RELEASEAARCH64_QEMU_EFI.fd",
            "target/RELEASEAARCH64_QEMU_EFI.fd",
        ),
    };

    let mut file = match std::fs::metadata(ovmf_path) {
        Err(e) if e.kind() == std::io::ErrorKind::NotFound => std::fs::OpenOptions::new()
            .create(true)
            .write(true)
            .read(true)
            .open(ovmf_path)
            .into_report()
            .change_context(OvmfFetchError::Io)?,
        Ok(_) => return Ok(ovmf_path.to_owned()),
        Err(e) => return Err(report!(e).change_context(OvmfFetchError::Io)),
    };
    let mut bytes = reqwest::blocking::get(ovmf_url)
        .into_report()
        .change_context(OvmfFetchError::Fetch)?;

    bytes
        .copy_to(&mut file)
        .into_report()
        .change_context(OvmfFetchError::Io)?;

    Ok(ovmf_path.to_owned())
}

#[derive(Debug, Display)]
enum OvmfFetchError {
    #[display(fmt = "Failed to fetch OVMF package")]
    Fetch,
    #[display(fmt = "No OVMF package available")]
    Empty,
    #[display(fmt = "IO Error")]
    Io,
}

impl Context for OvmfFetchError {}

#[derive(Clone, Copy, PartialEq, Eq)]
enum Target {
    X86_64,
    Riscv64Virt,
    Aarch64,
}

#[derive(Debug, Display)]
enum Error {
    #[display(fmt = "Failed to build the kernel")]
    Build,
    #[display(fmt = "Missing or invalid subcommand (available: build, run)")]
    InvalidSubCom,
    #[display(fmt = "IO Error")]
    Io,
    #[display(fmt = "Failed to spawn a process")]
    ProcessSpawn,
    #[display(fmt = "Failed to fetch UEFI firmware")]
    OvmfFetch,
    #[display(fmt = "QEMU Error: {}", "fmt_qemu_err(*_0)")]
    Qemu(Option<i32>),
}

impl Context for Error {}

fn fmt_qemu_err(e: Option<i32>) -> impl Display {
    struct W(Option<i32>);
    impl Display for W {
        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
            if let Some(c) = self.0 {
                c.fmt(f)
            } else {
                f.write_str("Interrupted by signal")
            }
        }
    }

    W(e)
}