#![deny(clippy::expect_used)]
#![deny(clippy::unwrap_used)]
#![deny(clippy::panic)]

use anyhow::{anyhow, bail, ensure, Result};
use cargo_metadata::MetadataCommand;
use clap::{crate_version, lazy_static::lazy_static, Clap};
use dylint_internal::{
    env::{self, var},
    Command,
};
use std::{
    collections::{BTreeMap, BTreeSet},
    env::consts,
    ffi::OsStr,
    fmt::Debug,
    fs::read_dir,
    path::{Path, PathBuf},
};

pub mod driver_builder;

mod error;
use error::warn;
pub use error::{ColorizedError, ColorizedResult};

lazy_static! {
    static ref REQUIRED_FORM: String = format!(
        r#""{}" LIBRARY_NAME "@" TOOLCHAIN "{}""#,
        consts::DLL_PREFIX,
        consts::DLL_SUFFIX
    );
}

type ToolchainMap = BTreeMap<String, BTreeSet<PathBuf>>;

pub type NameToolchainMap = BTreeMap<String, ToolchainMap>;

#[derive(Clap, Debug)]
struct Opts {
    #[clap(subcommand)]
    subcmd: SubCommand,
}

#[derive(Clap, Debug)]
enum SubCommand {
    Dylint(Dylint),
}

#[derive(Clap, Debug, Default)]
#[clap(
    version = crate_version!(),
    after_help = "ENVIRONMENT VARIABLES:

DYLINT_DRIVER_PATH (default: $HOME/.dylint_drivers) is the directory where Dylint stores rustc
drivers.

DYLINT_LIBRARY_PATH (default: none) is a colon-separated list of directories where Dylint searches
for libraries.
",
)]
pub struct Dylint {
    #[clap(long = "all", about = "Load all discovered libraries")]
    pub all: bool,

    #[clap(
        multiple = true,
        number_of_values = 1,
        long = "lib",
        value_name = "name",
        about = "Library name to load lints from. A file with a name of the form \"DLL_PREFIX \
        <name> '@' TOOLCHAIN DLL_SUFFIX\" is searched for in the directories listed in \
        DYLINT_LIBRARY_PATH and in the current package's `debug` and `release` directories."
    )]
    pub libs: Vec<String>,

    #[clap(
        long = "list",
        about = "If no libaries are named, list the name, toolchain, and location of all \
        discovered libraries. If at least one library is named, list the name, level, and \
        description of all lints in all named libraries. Combine with `--all` to list all \
        lints in all discovered libraries."
    )]
    pub list: bool,

    #[clap(
        multiple = true,
        number_of_values = 1,
        long = "path",
        value_name = "path",
        about = "Library path to load lints from"
    )]
    pub paths: Vec<String>,

    #[clap(short = 'q', long = "quiet", about = "Suppress warnings")]
    pub quiet: bool,

    #[clap(
        about = "Libraries to load lints from. Each <name> is searched for as described under \
        `--lib`. If no library is found, <name> is treated as path. To avoid ambiguity, use \
        `--lib` or `--path`."
    )]
    pub names: Vec<String>,

    #[clap(last = true, about = "Arguments for `cargo check`")]
    pub args: Vec<String>,
}

pub fn cargo_dylint<T: AsRef<OsStr>>(args: &[T]) -> ColorizedResult<()> {
    match Opts::parse_from(args).subcmd {
        SubCommand::Dylint(opts) => run(&opts),
    }
    .map_err(ColorizedError::new)
}

pub fn run(opts: &Dylint) -> Result<()> {
    let name_toolchain_map = name_toolchain_map()?;

    run_with_name_toolchain_map(opts, &name_toolchain_map)
}

pub fn name_toolchain_map() -> Result<NameToolchainMap> {
    let mut name_toolchain_map = NameToolchainMap::new();

    let dylint_library_paths = dylint_library_paths()?;
    let profile_paths = profile_paths();

    for path in dylint_library_paths.iter().chain(&profile_paths) {
        for entry in dylint_libraries_in(path)? {
            let (name, toolchain, path) = entry?;
            name_toolchain_map
                .entry(name)
                .or_insert_with(Default::default)
                .entry(toolchain)
                .or_insert_with(Default::default)
                .insert(path);
        }
    }

    Ok(name_toolchain_map)
}

fn dylint_library_paths() -> Result<Vec<PathBuf>> {
    let mut paths = Vec::new();

    if let Ok(val) = var(env::DYLINT_LIBRARY_PATH) {
        for path in val.split(':') {
            let path = PathBuf::from(path);
            ensure!(
                path.is_absolute(),
                "DYLINT_LIBRARY_PATH contains `{}`, which is not absolute",
                path.to_string_lossy()
            );
            ensure!(
                path.is_dir(),
                "DYLINT_LIBRARY_PATH contains `{}`, which is not a directory",
                path.to_string_lossy()
            );
            paths.push(path);
        }
    }

    Ok(paths)
}

fn profile_paths() -> Vec<PathBuf> {
    let mut paths = Vec::new();

    if let Ok(metadata) = MetadataCommand::new().no_deps().exec() {
        let debug = metadata.target_directory.join_os("debug");
        let release = metadata.target_directory.join_os("release");
        if debug.is_dir() {
            paths.push(debug);
        }
        if release.is_dir() {
            paths.push(release);
        }
    }

    paths
}

#[allow(clippy::option_if_let_else)]
fn dylint_libraries_in(
    path: &Path,
) -> Result<impl Iterator<Item = Result<(String, String, PathBuf)>>> {
    let iter = read_dir(path)?;
    Ok(iter
        .map(|entry| -> Result<Option<(String, String, PathBuf)>> {
            let entry = entry?;
            let path = entry.path();

            Ok(if let Some(filename) = path.file_name() {
                parse_filename(&filename.to_string_lossy())
                    .map(|(lib_name, toolchain)| (lib_name, toolchain, path))
            } else {
                None
            })
        })
        .filter_map(Result::transpose))
}

fn run_with_name_toolchain_map(opts: &Dylint, name_toolchain_map: &NameToolchainMap) -> Result<()> {
    if opts.list
        && opts.libs.is_empty()
        && opts.paths.is_empty()
        && opts.names.is_empty()
        && !opts.all
    {
        return list_libs(name_toolchain_map);
    }

    let resolved = resolve(opts, name_toolchain_map)?;

    if resolved.is_empty() {
        assert!(opts.libs.is_empty());
        assert!(opts.paths.is_empty());
        assert!(opts.names.is_empty());

        if name_toolchain_map.is_empty() {
            warn(opts, "No libraries were found.");
            return Ok(());
        }

        warn(opts, "Nothing to do. Did you forget `--all`?");
        return Ok(());
    }

    if opts.list {
        list_lints(opts, name_toolchain_map, &resolved)
    } else {
        check(opts, name_toolchain_map, &resolved)
    }
}

fn list_libs(name_toolchain_map: &NameToolchainMap) -> Result<()> {
    let name_width = name_toolchain_map
        .keys()
        .map(String::len)
        .max()
        .unwrap_or_default();

    let toolchain_width = name_toolchain_map
        .values()
        .flat_map(ToolchainMap::keys)
        .map(String::len)
        .max()
        .unwrap_or_default();

    for (name, toolchain_map) in name_toolchain_map {
        for (toolchain, paths) in toolchain_map {
            for path in paths {
                let parent = path
                    .parent()
                    .ok_or_else(|| anyhow!("Could not get parent directory"))?;
                println!(
                    "{:<name_width$} {:<toolchain_width$} {}",
                    name,
                    toolchain,
                    parent.to_string_lossy(),
                    name_width = name_width,
                    toolchain_width = toolchain_width
                );
            }
        }
    }

    Ok(())
}

#[allow(unknown_lints)]
#[allow(question_mark_in_expression)]
fn resolve(opts: &Dylint, name_toolchain_map: &NameToolchainMap) -> Result<ToolchainMap> {
    let mut toolchain_map = ToolchainMap::new();

    if opts.all {
        name_toolchain_map.values().cloned().for_each(|other| {
            for (toolchain, mut paths) in other {
                toolchain_map
                    .entry(toolchain)
                    .or_insert_with(Default::default)
                    .append(&mut paths);
            }
        });
    }

    for name in &opts.libs {
        ensure!(!opts.all, "`--lib` cannot be used with `--all`");
        let (toolchain, path) =
            name_as_lib(name_toolchain_map, name, true)?.unwrap_or_else(|| unreachable!());
        toolchain_map
            .entry(toolchain)
            .or_insert_with(Default::default)
            .insert(path);
    }

    for name in &opts.paths {
        let (toolchain, path) = name_as_path(name, true)?.unwrap_or_else(|| unreachable!());
        toolchain_map
            .entry(toolchain)
            .or_insert_with(Default::default)
            .insert(path);
    }

    for name in &opts.names {
        if let Some((toolchain, path)) = name_as_lib(name_toolchain_map, name, false)? {
            ensure!(
                !opts.all,
                "`{}` is a library name and cannot be used with `--all`; if a path was meant, use `--path {}`",
                name,
                name
            );
            toolchain_map
                .entry(toolchain)
                .or_insert_with(Default::default)
                .insert(path);
        } else if let Some((toolchain, path)) = name_as_path(name, false)? {
            toolchain_map
                .entry(toolchain)
                .or_insert_with(Default::default)
                .insert(path);
        } else {
            bail!("Could not find `{}`", name);
        }
    }

    Ok(toolchain_map)
}

pub fn name_as_lib(
    name_toolchain_map: &NameToolchainMap,
    name: &str,
    as_lib_only: bool,
) -> Result<Option<(String, PathBuf)>> {
    if !is_valid_lib_name(name) {
        ensure!(!as_lib_only, "`{}` is not a valid library name", name);
        return Ok(None);
    }

    if let Some(toolchain_map) = name_toolchain_map.get(name) {
        let mut toolchain_paths = flatten_toolchain_map(toolchain_map);

        return match toolchain_paths.len() {
            0 => Ok(None),
            1 => Ok(Some(toolchain_paths.remove(0))),
            _ => Err(anyhow!(
                "Found multiple libraries matching `{}`: {:?}",
                name,
                toolchain_paths
                    .iter()
                    .map(|(_, path)| path)
                    .collect::<Vec<_>>()
            )),
        };
    }

    ensure!(!as_lib_only, "Could not find `--lib {}`", name);

    Ok(None)
}

fn is_valid_lib_name(name: &str) -> bool {
    Path::new(name).file_name() == Some(OsStr::new(name))
}

fn name_as_path(name: &str, as_path_only: bool) -> Result<Option<(String, PathBuf)>> {
    if let Ok(path) = PathBuf::from(name).canonicalize() {
        if let Some(filename) = path.file_name() {
            if let Some((_, toolchain)) = parse_filename(&filename.to_string_lossy()) {
                return Ok(Some((toolchain, path)));
            }

            ensure!(
                !as_path_only,
                "`--path {}` was used, but the filename does not have the required form: {}",
                name,
                *REQUIRED_FORM
            );

            // smoelius: If `name` contains a path separator, then it was clearly meant to be a
            // path.
            ensure!(
                !name.contains(std::path::MAIN_SEPARATOR),
                "`{}` is a valid path, but the filename does not have the required form: {}",
                name,
                *REQUIRED_FORM
            );
        }

        ensure!(
            !as_path_only,
            "`--path {}` was used, but it is invalid",
            name
        );
    }

    ensure!(!as_path_only, "Could not find `--path {}`", name);

    Ok(None)
}

fn parse_filename(filename: &str) -> Option<(String, String)> {
    let file_stem = filename.strip_suffix(consts::DLL_SUFFIX)?;
    let target_name = file_stem.strip_prefix(consts::DLL_PREFIX)?;
    parse_target_name(target_name)
}

fn parse_target_name(target_name: &str) -> Option<(String, String)> {
    let mut iter = target_name.splitn(2, '@');
    let lib_name = iter.next()?;
    let toolchain = iter.next()?;
    Some((lib_name.to_owned(), toolchain.to_owned()))
}

fn list_lints(
    _opts: &Dylint,
    name_toolchain_map: &NameToolchainMap,
    resolved: &ToolchainMap,
) -> Result<()> {
    for (name, toolchain_map) in name_toolchain_map {
        for (toolchain, paths) in toolchain_map {
            for path in paths {
                if resolved
                    .get(toolchain)
                    .map_or(false, |paths| paths.contains(path))
                {
                    let driver = driver_builder::get(&toolchain)?;
                    let dylint_libs = serde_json::to_string(&[path])?;

                    print!("{}", name);
                    if toolchain_map.keys().len() >= 2 {
                        print!("@{}", toolchain);
                    }
                    if paths.len() >= 2 {
                        let parent = path
                            .parent()
                            .ok_or_else(|| anyhow!("Could not get parent directory"))?;
                        print!(" ({})", parent.to_string_lossy());
                    }
                    println!();

                    // smoelius: `-W help` is the normal way to list lints, so we can be sure it
                    // gets the lints loaded. However, we don't actually use it to list the lints.
                    Command::new(driver)
                        .envs(vec![
                            (env::DYLINT_LIBS.to_owned(), dylint_libs),
                            (env::DYLINT_LIST.to_owned(), "1".to_owned()),
                        ])
                        .args(vec!["rustc", "-W", "help"])
                        .success()?;

                    println!();
                }
            }
        }
    }

    Ok(())
}

fn check(
    opts: &Dylint,
    _name_toolchain_map: &NameToolchainMap,
    resolved: &ToolchainMap,
) -> Result<()> {
    let clippy_disable_docs_links = clippy_disable_docs_links()?;

    for (toolchain, paths) in resolved {
        let driver = driver_builder::get(&toolchain)?;
        let dylint_libs = serde_json::to_string(&paths)?;

        // smoelius: Set CLIPPY_DISABLE_DOCS_LINKS to prevent lints from accidentally linking to the
        // Clippy repository. But set it to the JSON-encoded original value so that the Clippy
        // library can unset the variable.
        // smoelius: This doesn't work if another library is loaded alongside Clippy.
        // smoelius: This was fixed in `clippy_utils`:
        // https://github.com/rust-lang/rust-clippy/commit/1a206fc4abae0b57a3f393481367cf3efca23586
        // But I am going to continue to set CLIPPY_DISABLE_DOCS_LINKS because it doesn't seem to
        // hurt and it provides a small amount of backward compatibility.
        dylint_internal::check()
            .envs(vec![
                (
                    env::CLIPPY_DISABLE_DOCS_LINKS.to_owned(),
                    clippy_disable_docs_links.clone(),
                ),
                (env::DYLINT_LIBS.to_owned(), dylint_libs),
                (
                    env::RUSTC_WORKSPACE_WRAPPER.to_owned(),
                    driver.to_string_lossy().to_string(),
                ),
                (env::RUSTUP_TOOLCHAIN.to_owned(), toolchain.clone()),
            ])
            .args(opts.args.clone())
            .success()?;
    }

    Ok(())
}

fn flatten_toolchain_map(toolchain_map: &ToolchainMap) -> Vec<(String, PathBuf)> {
    toolchain_map
        .iter()
        .flat_map(|(toolchain, paths)| {
            paths
                .iter()
                .map(|path| (toolchain.clone(), path.clone()))
                .collect::<Vec<_>>()
        })
        .collect()
}

fn clippy_disable_docs_links() -> Result<String> {
    let val = var(env::CLIPPY_DISABLE_DOCS_LINKS).ok();
    serde_json::to_string(&val).map_err(Into::into)
}

#[cfg(test)]
mod test {
    #![allow(clippy::unwrap_used)]

    use super::*;
    use dylint_examples as examples;
    use lazy_static::lazy_static;
    use std::env::set_var;
    use test_env_log::test;

    lazy_static! {
        static ref NAME_TOOLCHAIN_MAP: NameToolchainMap = {
            examples::build().unwrap();
            let dylint_library_path = examples::iter()
                .unwrap()
                .map(|example| {
                    example
                        .unwrap()
                        .join("target")
                        .join("debug")
                        .to_string_lossy()
                        .to_string()
                })
                .collect::<Vec<_>>()
                .join(":");
            set_var(env::DYLINT_LIBRARY_PATH, dylint_library_path);
            name_toolchain_map().unwrap()
        };
    }

    #[test]
    fn multiple_libraries_multiple_toolchains() {
        let allow_clippy = NAME_TOOLCHAIN_MAP.get("allow_clippy").unwrap();
        let question_mark_in_expression = NAME_TOOLCHAIN_MAP
            .get("question_mark_in_expression")
            .unwrap();

        assert_ne!(
            allow_clippy.keys().collect::<Vec<_>>(),
            question_mark_in_expression.keys().collect::<Vec<_>>()
        );

        let opts = Dylint {
            libs: vec![
                "allow_clippy".to_owned(),
                "question_mark_in_expression".to_owned(),
            ],
            ..Dylint::default()
        };

        run_with_name_toolchain_map(&opts, &NAME_TOOLCHAIN_MAP).unwrap();
    }

    // smoelius: Check that loading multiple libraries with the same Rust toolchain works. At one point,
    // I was getting this error from `libloading`:
    //
    //   cannot allocate memory in static TLS block
    //
    // The culprit turned out to be the `rand` crate, which uses a lot of thread local storage. `rand`
    // is used by `tempfile`, which is used by various Rust compiler crates. Essentially, each library
    // had its own copy of the Rust compiler, and therefore its own copy of the `rand` crate, and this
    // was eating up all the thread local storage.
    //
    // The solution was to add `extern crate rustc_driver` to each library. This causes the library to
    // link against `librust_driver.so`, which dylint-driver also links against. So, essentially, each
    // library now uses dylint-driver's copy of the `rand` crate.
    //
    // This thread was very helpful in diagnosing the problem:
    //
    //   https://bugzilla.redhat.com/show_bug.cgi?id=1722181
    //
    #[test]
    fn multiple_libraries_one_toolchain() {
        let clippy = NAME_TOOLCHAIN_MAP.get("clippy").unwrap();
        let question_mark_in_expression = NAME_TOOLCHAIN_MAP
            .get("question_mark_in_expression")
            .unwrap();

        assert_eq!(
            clippy.keys().collect::<Vec<_>>(),
            question_mark_in_expression.keys().collect::<Vec<_>>()
        );

        let opts = Dylint {
            libs: vec![
                "clippy".to_owned(),
                "question_mark_in_expression".to_owned(),
            ],
            ..Dylint::default()
        };

        run_with_name_toolchain_map(&opts, &NAME_TOOLCHAIN_MAP).unwrap();
    }
}