use super::generate::parse_grammar::GrammarJSON;
use anyhow::{anyhow, Context, Result};
use std::ffi::{OsStr, OsString};
use std::fs;
use std::path::Path;
use std::process::Command;
use which::which;

const EMSCRIPTEN_TAG: &'static str = concat!("emscripten/emsdk:", env!("EMSCRIPTEN_VERSION"));

pub fn get_grammar_name(src_dir: &Path) -> Result<String> {
    let grammar_json_path = src_dir.join("grammar.json");
    let grammar_json = fs::read_to_string(&grammar_json_path)
        .with_context(|| format!("Failed to read grammar file {:?}", grammar_json_path))?;
    let grammar: GrammarJSON = serde_json::from_str(&grammar_json)
        .with_context(|| format!("Failed to parse grammar file {:?}", grammar_json_path))?;
    Ok(grammar.name)
}

pub fn compile_language_to_wasm(language_dir: &Path, force_docker: bool) -> Result<()> {
    let src_dir = language_dir.join("src");
    let grammar_name = get_grammar_name(&src_dir)?;
    let output_filename = format!("tree-sitter-{}.wasm", grammar_name);

    let emcc_bin = if cfg!(windows) { "emcc.bat" } else { "emcc" };
    let emcc_path = which(emcc_bin)
        .ok()
        .and_then(|p| Command::new(&p).output().and(Ok(p)).ok());

    let mut command;
    if !force_docker && emcc_path.is_some() {
        command = Command::new(emcc_path.unwrap());
        command.current_dir(&language_dir);
    } else if Command::new("docker").output().is_ok() {
        command = Command::new("docker");
        command.args(&["run", "--rm"]);

        // Mount the parser directory as a volume
        let mut volume_string;
        if let (Some(parent), Some(filename)) = (language_dir.parent(), language_dir.file_name()) {
            volume_string = OsString::from(parent);
            volume_string.push(":/src:Z");
            command.arg("--workdir");
            command.arg(&Path::new("/src").join(filename));
        } else {
            volume_string = OsString::from(language_dir);
            volume_string.push(":/src:Z");
            command.args(&["--workdir", "/src"]);
        }

        command.args(&[OsStr::new("--volume"), &volume_string]);

        // Get the current user id so that files created in the docker container will have
        // the same owner.
        if cfg!(unix) {
            let user_id_output = Command::new("id")
                .arg("-u")
                .output()
                .with_context(|| "Failed to get get current user id")?;
            let user_id = String::from_utf8_lossy(&user_id_output.stdout);
            let user_id = user_id.trim();
            command.args(&["--user", user_id]);
        }

        // Run `emcc` in a container using the `emscripten-slim` image
        command.args(&[EMSCRIPTEN_TAG, "emcc"]);
    } else {
        return Err(anyhow!(
            "You must have either emcc or docker on your PATH to run this command"
        ));
    }

    command.args(&[
        "-o",
        &output_filename,
        "-Os",
        "-s",
        "WASM=1",
        "-s",
        "SIDE_MODULE=1",
        "-s",
        "TOTAL_MEMORY=33554432",
        "-s",
        "NODEJS_CATCH_EXIT=0",
        "-s",
        &format!("EXPORTED_FUNCTIONS=[\"_tree_sitter_{}\"]", grammar_name),
        "-fno-exceptions",
        "-I",
        "src",
    ]);

    let src = Path::new("src");
    let parser_c_path = src.join("parser.c");
    let scanner_c_path = src.join("scanner.c");
    let scanner_cc_path = src.join("scanner.cc");
    let scanner_cpp_path = src.join("scanner.cpp");

    if language_dir.join(&scanner_cc_path).exists() {
        command.arg("-xc++").arg(&scanner_cc_path);
    } else if language_dir.join(&scanner_cpp_path).exists() {
        command.arg("-xc++").arg(&scanner_cpp_path);
    } else if language_dir.join(&scanner_c_path).exists() {
        command.arg(&scanner_c_path);
    }

    command.arg(&parser_c_path);

    let output = command
        .output()
        .with_context(|| "Failed to run emcc command")?;
    if !output.status.success() {
        return Err(anyhow!(
            "emcc command failed - {}",
            String::from_utf8_lossy(&output.stderr)
        ));
    }

    // Move the created `.wasm` file into the current working directory.
    fs::rename(&language_dir.join(&output_filename), &output_filename)
        .with_context(|| format!("Couldn't find output file {:?}", output_filename))?;

    Ok(())
}
