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// Copyright 2017 The RLS Project Developers.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! Defines an `AnalysisLoader` trait, which allows to specify directories
//! from which save-analysis JSON files can be read. Also supplies a
//! default implementation `CargoAnalysisLoader` for Cargo-emitted save-analysis
//! files.

use std::env;
use std::ffi::OsStr;
use std::fmt;
use std::path::{Path, PathBuf};
use std::process::Command;

use AnalysisHost;

#[derive(Debug)]
pub struct CargoAnalysisLoader {
    pub path_prefix: Option<PathBuf>,
    pub target: Target,
}

impl CargoAnalysisLoader {
    pub fn new(target: Target) -> CargoAnalysisLoader {
        CargoAnalysisLoader {
            path_prefix: None,
            target,
        }
    }
}

/// Allows to specify from where and which analysis files will be considered
/// when reloading data to lower.
pub trait AnalysisLoader: Sized {
    fn needs_hard_reload(&self, path_prefix: &Path) -> bool;
    fn fresh_host(&self) -> AnalysisHost<Self>;
    fn set_path_prefix(&mut self, path_prefix: &Path);
    fn abs_path_prefix(&self) -> Option<PathBuf>;
    /// Returns every directory in which analysis files are to be considered.
    fn search_directories(&self) -> Vec<PathBuf>;
}

impl AnalysisLoader for CargoAnalysisLoader {
    fn needs_hard_reload(&self, path_prefix: &Path) -> bool {
        self.path_prefix.as_ref().map_or(true, |p| p != path_prefix)
    }

    fn fresh_host(&self) -> AnalysisHost<Self> {
        AnalysisHost::new_with_loader(CargoAnalysisLoader {
            path_prefix: self.path_prefix.clone(),
            .. CargoAnalysisLoader::new(self.target)
        })
    }

    fn set_path_prefix(&mut self, path_prefix: &Path) {
        self.path_prefix = Some(path_prefix.to_owned());
    }

    fn abs_path_prefix(&self) -> Option<PathBuf> {
        self.path_prefix.as_ref()
            .map(|s| Path::new(s).canonicalize().unwrap().to_owned())
    }

    fn search_directories(&self) -> Vec<PathBuf> {
        let path_prefix = self.path_prefix.as_ref().unwrap();
        let target = self.target.to_string();

        // TODO sys_root_path allows to break out of 'sandbox' - is that Ok?
        let principle_path = path_prefix
            .join("target")
            .join("rls")
            .join(&target)
            .join("save-analysis");
        let deps_path = path_prefix
            .join("target")
            .join("rls")
            .join(&target)
            .join("deps")
            .join("save-analysis");
        let sys_root_path = sys_root_path();
        let target_triple = extract_target_triple(sys_root_path.as_path());
        let libs_path = sys_root_path
            .join("lib")
            .join("rustlib")
            .join(&target_triple)
            .join("analysis");

        vec![libs_path, deps_path, principle_path]
    }
}

// FIXME: This can fail when using a custom toolchain in rustup (often linked to
// `/$rust_repo/build/$target/stage2`)
fn extract_target_triple(sys_root_path: &Path) -> String {
    // Extracts nightly-x86_64-pc-windows-msvc from
    // $HOME/.rustup/toolchains/nightly-x86_64-pc-windows-msvc
    let toolchain = sys_root_path
        .iter()
        .last()
        .and_then(OsStr::to_str)
        .expect("extracting toolchain failed");
    // Extracts x86_64-pc-windows-msvc from nightly-x86_64-pc-windows-pc
    let triple = toolchain
        .splitn(2, '-')
        .last()
        .map(String::from)
        .expect("extracting triple failed");
    triple
}

fn sys_root_path() -> PathBuf {
    env::var("SYSROOT")
        .ok()
        .map(PathBuf::from)
        .or_else(|| {
            Command::new(env::var("RUSTC").unwrap_or(String::from("rustc")))
                .arg("--print")
                .arg("sysroot")
                .output()
                .ok()
                .and_then(|out| String::from_utf8(out.stdout).ok())
                .map(|s| PathBuf::from(s.trim()))
        })
        .expect("need to specify SYSROOT or RUSTC env vars, or rustc must be in PATH")
}

#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum Target {
    Release,
    Debug,
}

impl fmt::Display for Target {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Target::Release => write!(f, "release"),
            Target::Debug => write!(f, "debug"),
        }
    }
}

#[cfg(test)]
mod tests {
    use std::path::Path;
    use super::*;

    #[test]
    fn windows_path() {
        let path = Path::new(
            r#"C:\Users\user\.rustup\toolchains\nightly-x86_64-pc-windows-msvc"#,
        );
        assert_eq!(
            extract_target_triple(path),
            String::from("x86_64-pc-windows-msvc")
        );
    }

    #[test]
    fn unix_path() {
        let path = Path::new(
            "/home/user/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu",
        );
        assert_eq!(
            extract_target_triple(path),
            String::from("x86_64-unknown-linux-gnu")
        );
    }
}