use cargo_metadata::{MetadataCommand, Package};
use rustc_version::{Channel, Version};
use std::path::{Path, PathBuf};
use std::{
    env, fmt, io,
    process::{self, Command, Stdio},
};

#[derive(serde_derive::Deserialize, Default)]
struct CTRConfig {
    name: String,
    author: String,
    description: String,
    icon: String,
    target_path: String,
    cargo_manifest_path: PathBuf,
}

#[derive(Ord, PartialOrd, PartialEq, Eq, Debug)]
struct CommitDate {
    year: i32,
    month: i32,
    day: i32,
}

impl CommitDate {
    fn parse(date: &str) -> Option<Self> {
        let mut iter = date.split('-');

        let year = iter.next()?.parse().ok()?;
        let month = iter.next()?.parse().ok()?;
        let day = iter.next()?.parse().ok()?;

        Some(Self { year, month, day })
    }
}

impl fmt::Display for CommitDate {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{:04}-{:02}-{:02}", self.year, self.month, self.day)
    }
}

const MINIMUM_COMMIT_DATE: CommitDate = CommitDate {
    year: 2021,
    month: 10,
    day: 1,
};
const MINIMUM_RUSTC_VERSION: Version = Version::new(1, 56, 0);

fn main() {
    check_rust_version();

    if env::args().any(|arg| arg == "--help" || arg == "-h") {
        print_usage(&mut io::stdout());
        return;
    }

    let optimization_level = if env::args().any(|arg| arg == "--release") {
        String::from("release")
    } else {
        String::from("debug")
    };

    // Skip `cargo 3ds`
    let mut args = env::args().skip(2);

    // Get the command and collect the remaining arguments
    let command = args.next();
    let args: Vec<String> = args.collect();
    let args: Vec<&str> = args.iter().map(String::as_str).collect();

    let (command, must_link) = match command.as_deref() {
        Some("link") => ("build", true),
        Some(command) => (command, false),
        None => {
            print_usage(&mut io::stderr());
            process::exit(2)
        }
    };

    eprintln!("Running Cargo");
    build_elf(command, &args);

    if command != "build" && !must_link {
        // We only do more work if it's a build or build + 3dslink operation
        return;
    }

    eprintln!("Getting metadata");
    let app_conf = get_metadata(&args, &optimization_level);

    eprintln!("Building smdh");
    build_smdh(&app_conf);

    eprintln!("Building 3dsx");
    build_3dsx(&app_conf);

    if must_link {
        eprintln!("Running 3dslink");
        link(&app_conf);
    }
}

fn print_usage(f: &mut impl std::io::Write) {
    let invocation = {
        let mut args = std::env::args();

        // We do this to properly display `cargo-3ds` if invoked that way
        let bin = args.next().unwrap();
        if let Some("3ds") = args.next().as_deref() {
            "cargo 3ds".to_string()
        } else {
            bin
        }
    };

    writeln!(
        f,
        "{name}: {description}.

Usage:
    {invocation} build [--release] [CARGO_OPTS...]
    {invocation} link [--release] [CARGO_OPTS...]
    {invocation} <cargo-command> [CARGO_OPTS...]
    {invocation} -h | --help

Commands:
    build           build a 3dsx executable.
    link            build a 3dsx executable and send it to a device with 3dslink.
    <cargo-command> execute some other Cargo command with 3ds options configured (ex. check or clippy).

Options:
    -h --help       Show this screen.
    --release       Build in release mode.

Additional arguments will be passed through to `cargo build`.
",
        name = env!("CARGO_BIN_NAME"),
        description = env!("CARGO_PKG_DESCRIPTION"),
        invocation = invocation,
    )
    .unwrap();
}

fn check_rust_version() {
    let rustc_version = rustc_version::version_meta().unwrap();

    if rustc_version.channel > Channel::Nightly {
        println!("cargo-3ds requires a nightly rustc version.");
        println!(
            "Please run `rustup override set nightly` to use nightly in the \
            current directory."
        );
        process::exit(1);
    }

    let old_version: bool = MINIMUM_RUSTC_VERSION > rustc_version.semver;

    let old_commit = match rustc_version.commit_date {
        None => false,
        Some(date) => {
            MINIMUM_COMMIT_DATE
                > CommitDate::parse(&date).expect("could not parse `rustc --version` commit date")
        }
    };

    if old_version || old_commit {
        println!(
            "cargo-3ds requires rustc nightly version >= {}",
            MINIMUM_COMMIT_DATE,
        );
        println!("Please run `rustup update nightly` to upgrade your nightly version");

        process::exit(1);
    }
}

fn build_elf(command: &str, args: &[&str]) {
    let rustflags = env::var("RUSTFLAGS").unwrap_or_default()
        + &format!(" -L{}/libctru/lib -lctru", env::var("DEVKITPRO").unwrap());

    let mut process = Command::new("cargo")
        .arg(command)
        .arg("-Z")
        .arg("build-std")
        .arg("--target")
        .arg("armv6k-nintendo-3ds")
        .args(args)
        .env("RUSTFLAGS", rustflags)
        .stdin(Stdio::inherit())
        .stdout(Stdio::inherit())
        .stderr(Stdio::inherit())
        .spawn()
        .unwrap();

    let status = process.wait().unwrap();

    if !status.success() {
        process::exit(status.code().unwrap_or(1));
    }
}

fn get_metadata(args: &[&str], opt_level: &str) -> CTRConfig {
    let metadata = MetadataCommand::new()
        .exec()
        .expect("Failed to get cargo metadata");
    let target_dir = &metadata.target_directory;

    let package: &Package;
    let binary_name: String;
    let target_path: String;

    // Check if we compiled the crate or an example
    if let Some(example_pos) = args.iter().position(|arg| *arg == "--example") {
        let example_name = *args.get(example_pos + 1).expect("No example given");

        // Find the example's package
        package = metadata
            .packages
            .iter()
            .find(|pkg| {
                pkg.targets.iter().any(|target| {
                    target.name == example_name && target.kind.iter().any(|kind| kind == "example")
                })
            })
            .expect("Could not find package for example");

        binary_name = format!("{} - {} example", example_name, package.name);
        target_path = format!(
            "{}/armv6k-nintendo-3ds/{}/examples/{}",
            target_dir, opt_level, example_name
        );
    } else {
        // Otherwise get the current/root crate
        package = metadata.root_package().expect("No root crate found");
        binary_name = package.name.clone();
        target_path = format!(
            "{}/armv6k-nintendo-3ds/{}/{}",
            target_dir, opt_level, package.name
        );
    }

    let mut icon = String::from("./icon.png");

    if !Path::new(&icon).exists() {
        icon = format!(
            "{}/libctru/default_icon.png",
            env::var("DEVKITPRO").unwrap()
        );
    }

    CTRConfig {
        name: binary_name,
        author: package.authors[0].clone(),
        description: package
            .description
            .clone()
            .unwrap_or_else(|| String::from("Homebrew Application")),
        icon,
        target_path,
        cargo_manifest_path: package.manifest_path.clone().into(),
    }
}

fn build_smdh(config: &CTRConfig) {
    let mut process = Command::new("smdhtool")
        .arg("--create")
        .arg(&config.name)
        .arg(&config.description)
        .arg(&config.author)
        .arg(&config.icon)
        .arg(format!("{}.smdh", config.target_path))
        .stdin(Stdio::inherit())
        .stdout(Stdio::inherit())
        .stderr(Stdio::inherit())
        .spawn()
        .unwrap();

    let status = process.wait().unwrap();

    if !status.success() {
        process::exit(status.code().unwrap_or(1));
    }
}

fn build_3dsx(config: &CTRConfig) {
    let mut command = Command::new("3dsxtool");
    let mut process = command
        .arg(format!("{}.elf", config.target_path))
        .arg(format!("{}.3dsx", config.target_path))
        .arg(format!("--smdh={}.smdh", config.target_path));

    // If romfs directory exists, automatically include it
    let (romfs_path, is_default_romfs) = get_romfs_path(config);
    if romfs_path.is_dir() {
        println!("Adding RomFS from {}", romfs_path.display());
        process = process.arg(format!("--romfs={}", romfs_path.display()));
    } else if !is_default_romfs {
        eprintln!(
            "Could not find configured RomFS dir: {}",
            romfs_path.display()
        );
        process::exit(1);
    }

    let mut process = process
        .stdin(Stdio::inherit())
        .stdout(Stdio::inherit())
        .stderr(Stdio::inherit())
        .spawn()
        .unwrap();

    let status = process.wait().unwrap();

    if !status.success() {
        process::exit(status.code().unwrap_or(1));
    }
}

fn link(config: &CTRConfig) {
    let mut process = Command::new("3dslink")
        .arg(format!("{}.3dsx", config.target_path))
        .stdin(Stdio::inherit())
        .stdout(Stdio::inherit())
        .stderr(Stdio::inherit())
        .spawn()
        .unwrap();

    let status = process.wait().unwrap();

    if !status.success() {
        process::exit(status.code().unwrap_or(1));
    }
}

/// Read the RomFS path from the Cargo manifest. If it's unset, use the default.
/// The returned boolean is true when the default is used.
fn get_romfs_path(config: &CTRConfig) -> (PathBuf, bool) {
    let manifest_path = &config.cargo_manifest_path;
    let manifest_str = std::fs::read_to_string(manifest_path)
        .unwrap_or_else(|e| panic!("Could not open {}: {e}", manifest_path.display()));
    let manifest_data: toml::Value =
        toml::de::from_str(&manifest_str).expect("Could not parse Cargo manifest as TOML");

    // Find the romfs setting and compute the path
    let mut is_default = false;
    let romfs_dir_setting = manifest_data
        .as_table()
        .and_then(|table| table.get("package"))
        .and_then(toml::Value::as_table)
        .and_then(|table| table.get("metadata"))
        .and_then(toml::Value::as_table)
        .and_then(|table| table.get("cargo-3ds"))
        .and_then(toml::Value::as_table)
        .and_then(|table| table.get("romfs_dir"))
        .and_then(toml::Value::as_str)
        .unwrap_or_else(|| {
            is_default = true;
            "romfs"
        });
    let mut romfs_path = manifest_path.clone();
    romfs_path.pop(); // Pop Cargo.toml
    romfs_path.push(romfs_dir_setting);

    (romfs_path, is_default)
}