extern crate clap;
#[macro_use]
extern crate failure;
extern crate tera;
extern crate ron;
extern crate walkdir;
extern crate itertools;

use std::{
    fs,
    path::{Path},
    collections::HashSet,
};
use clap::{App, Arg, SubCommand};
use itertools::Itertools;

type Result<T> = ::std::result::Result<T, failure::Error>;

const GRAMMAR_DIR: &str = "./src/parser/grammar";
const INLINE_TESTS_DIR: &str = "tests/data/parser/inline";
const GRAMMAR: &str = "./src/grammar.ron";
const SYNTAX_KINDS: &str = "./src/syntax_kinds/generated.rs";
const SYNTAX_KINDS_TEMPLATE: &str = "./src/syntax_kinds/generated.rs.tera";

fn main() -> Result<()> {
    let matches = App::new("tasks")
        .setting(clap::AppSettings::SubcommandRequiredElseHelp)
        .arg(
            Arg::with_name("verify")
                .long("--verify")
                .help("Verify that generated code is up-to-date")
                .global(true)
        )
        .subcommand(SubCommand::with_name("gen-kinds"))
        .subcommand(SubCommand::with_name("gen-tests"))
        .get_matches();
    match matches.subcommand() {
        (name, Some(matches)) => run_gen_command(name, matches.is_present("verify"))?,
        _ => unreachable!(),
    }
    Ok(())
}

fn run_gen_command(name: &str, verify: bool) -> Result<()> {
    match name {
        "gen-kinds" => update(Path::new(SYNTAX_KINDS), &get_kinds()?, verify),
        "gen-tests" => gen_tests(verify),
        _ => unreachable!(),
    }
}

fn update(path: &Path, contents: &str, verify: bool) -> Result<()> {
    match fs::read_to_string(path) {
        Ok(ref old_contents) if old_contents == contents => {
            return Ok(());
        }
        _ => (),
    }
    if verify {
        bail!("`{}` is not up-to-date", path.display());
    }
    fs::write(path, contents)?;
    Ok(())
}

fn get_kinds() -> Result<String> {
    let grammar = grammar()?;
    let template = fs::read_to_string(SYNTAX_KINDS_TEMPLATE)?;
    let ret = tera::Tera::one_off(&template, &grammar, false).map_err(|e| {
        format_err!("template error: {}", e)
    })?;
    Ok(ret)
}

fn grammar() -> Result<ron::value::Value> {
    let text = fs::read_to_string(GRAMMAR)?;
    let ret = ron::de::from_str(&text)?;
    Ok(ret)
}

fn gen_tests(verify: bool) -> Result<()> {
    let tests = tests_from_dir(Path::new(GRAMMAR_DIR))?;

    let inline_tests_dir = Path::new(INLINE_TESTS_DIR);
    if !inline_tests_dir.is_dir() {
        fs::create_dir_all(inline_tests_dir)?;
    }
    let existing = existing_tests(inline_tests_dir)?;

    for t in existing.difference(&tests) {
        panic!("Test is deleted: {}\n{}", t.name, t.text);
    }

    let new_tests = tests.difference(&existing);
    for (i, t) in new_tests.enumerate() {
        let name = format!("{:04}_{}.rs", existing.len() + i + 1, t.name);
        let path = inline_tests_dir.join(name);
        update(&path, &t.text, verify)?;
    }
    Ok(())
}

#[derive(Debug, Eq)]
struct Test {
    name: String,
    text: String,
}

impl PartialEq for Test {
    fn eq(&self, other: &Test) -> bool {
        self.name.eq(&other.name)
    }
}

impl ::std::hash::Hash for Test {
    fn hash<H: ::std::hash::Hasher>(&self, state: &mut H) {
        self.name.hash(state)
    }
}

fn tests_from_dir(dir: &Path) -> Result<HashSet<Test>> {
    let mut res = HashSet::new();
    for entry in ::walkdir::WalkDir::new(dir) {
        let entry = entry.unwrap();
        if !entry.file_type().is_file() {
            continue;
        }
        if entry.path().extension().unwrap_or_default() != "rs" {
            continue;
        }
        let text = fs::read_to_string(entry.path())?;

        for test in collect_tests(&text) {
            if let Some(old_test) = res.replace(test) {
                bail!("Duplicate test: {}", old_test.name)
            }
        }
    }
    Ok(res)
}

fn collect_tests(s: &str) -> Vec<Test> {
    let mut res = vec![];
    let prefix = "// ";
    let comment_blocks = s.lines()
        .map(str::trim_left)
        .group_by(|line| line.starts_with(prefix));

    'outer: for (is_comment, block) in comment_blocks.into_iter() {
        if !is_comment {
            continue;
        }
        let mut block = block.map(|line| &line[prefix.len()..]);

        let name = loop {
            match block.next() {
                Some(line) if line.starts_with("test ") => break line["test ".len()..].to_string(),
                Some(_) => (),
                None => continue 'outer,
            }
        };
        let text: String = itertools::join(block.chain(::std::iter::once("")), "\n");
        assert!(!text.trim().is_empty() && text.ends_with("\n"));
        res.push(Test { name, text })
    }
    res
}

fn existing_tests(dir: &Path) -> Result<HashSet<Test>> {
    let mut res = HashSet::new();
    for file in fs::read_dir(dir)? {
        let file = file?;
        let path = file.path();
        if path.extension().unwrap_or_default() != "rs" {
            continue;
        }
        let name = path.file_name().unwrap().to_str().unwrap();
        let name = name["0000_".len()..name.len() - 3].to_string();
        let text = fs::read_to_string(&path)?;
        res.insert(Test { name, text });
    }
    Ok(res)
}