// Copyright 2019 Marcus Geiger
//
// 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.

/*!
This crate provides a simple regular expression based parsing library
for reading the `.gitmodules` file of a Git repository.

# Usage

Add this to your `Cargo.toml`:

``` toml
[dependencies]
gitmodules = "0.1"
```

Usage is trivial:
``` rust
use std::io::BufReader;
use gitmodules::{read_gitmodules, Submodule};

fn demo() {
    let text = r#"
# this is a comment line
[submodule "foo"]
    path = "some/path"
"#
    .as_bytes();
    let text = BufReader::new(text);
    let submodules = read_gitmodules(text).unwrap();
    println!("Submodule name {}", submodules.first().unwrap().name());
}
```
*/

#[macro_use]
extern crate log;
#[macro_use]
extern crate lazy_static;

use regex::Regex;
use std::io::prelude::*;

/// Represents a Git submodule entry with its attributes.
#[derive(Debug)]
pub struct Submodule {
    name: String,
    entries: Vec<(String, String)>,
}

#[allow(dead_code)]
impl Submodule {
    pub fn new(name: &str, entries: Vec<(String, String)>) -> Self {
        return Submodule {
            name: name.to_string(),
            entries: entries,
        };
    }

    /// Returns the name of the submodule. The name is the only
    /// required attribute of the submodule.
    pub fn name(&self) -> &str {
        &self.name
    }

    /// Returns the optional path of the Git submodule in the Git
    /// repository.
    pub fn path(&self) -> Option<String> {
        for (k, v) in &self.entries {
            if k == "path" {
                return Some(v.clone());
            }
        }
        return None;
    }

    /// Returns the optional entries of the Git submodule, excluding
    /// its name.
    pub fn entries(&self) -> &Vec<(String, String)> {
        &self.entries
    }
}

lazy_static! {
    // Note: be lenient about white spaces, although a proper
    // gitmodules file looks different.
    static ref RE_COMMENT: Regex = Regex::new(r#"^\s*#.*"#).unwrap();
    static ref RE_MODULE: Regex = Regex::new(r#"^\[submodule\s*"([^""]+)"\s*\]"#).unwrap();
    static ref RE_MODULE_ENTRY: Regex = Regex::new(r#"^\s*(\S+)\s*=\s*(.*)\s*"#).unwrap();
}

/// Read a `.gitmodules` file and return a vector of the configured
/// Git submodules.
pub fn read_gitmodules<R>(reader: R) -> std::io::Result<Vec<Submodule>>
where
    R: BufRead,
{
    let mut submodules: Vec<Submodule> = Vec::new();

    let mut module_name: Option<String> = None;
    let mut module_entries: Vec<(String, String)> = Vec::new();

    for (n, line) in reader.lines().enumerate() {
        let line = line.unwrap();
        let line = line.trim();
        if line.is_empty() {
            continue;
        }
        trace!("Parsing line {}: '{}'", n, &line);
        if RE_COMMENT.is_match(&line) {
            continue;
        } else if let Some(capture) = RE_MODULE.captures(&line) {
            let submodule_name = capture.get(1).unwrap().as_str();
            if let Some(name) = module_name.clone() {
                let submodule = Submodule::new(&name, module_entries.clone());
                submodules.push(submodule);
            }
            module_name = Some(submodule_name.to_string());
            module_entries = Vec::new();
        } else if let Some(capture) = RE_MODULE_ENTRY.captures(&line) {
            let key = capture.get(1).unwrap().as_str();
            let val = capture.get(2).unwrap().as_str();
            module_entries.push((key.to_string(), val.to_string()));
        } else {
            error!("ERROR: invalid line {}: '{}'", n, line);
        }
    }

    if let Some(name) = module_name {
        let submodule = Submodule::new(&name, module_entries.clone());
        submodules.push(submodule);
    }

    Ok(submodules)
}

#[cfg(test)]
mod tests {
    use std::io::BufReader;

    use super::*;

    use std::sync::{Once, ONCE_INIT};

    static INIT: Once = ONCE_INIT;

    /// Setup function that is only run once, even if called multiple times.
    fn setup() {
        INIT.call_once(|| {
            env_logger::init();
        });
    }

    #[test]
    fn gitmodules_with_comments() {
        setup();

        let text = r#"
# this is a comment line
[submodule "foo"]
	path = "some/path"
"#
        .as_bytes();
        let text = BufReader::new(text);
        let submodules = read_gitmodules(text).unwrap();

        assert_eq!(1, submodules.len());

        let module = submodules.first().unwrap();
        assert_eq!("foo", module.name());
        assert_eq!("\"some/path\"", module.path().unwrap());
    }

    #[test]
    fn gitmodules_with_broken_lines() {
        setup();

        let text = r#"
# the next line is normally invalid because of the missing white space before the identifier
  [submodule"foo"]
   [submodule	"bar"]

path="bar/path"
 one = 1
  two=2
[submodule "baz"]
	path = "baz/path"
	flag = true
"#
        .as_bytes();
        let text = BufReader::new(text);
        let submodules = read_gitmodules(text).unwrap();

        assert_eq!(3, submodules.len());

        let module = submodules.first().unwrap();
        assert_eq!("foo", module.name());
        assert!(module.entries().is_empty());

        let module = submodules.get(1).unwrap();
        assert_eq!("bar", module.name());
        assert_eq!("\"bar/path\"", module.path().unwrap());
        let actual_one = module.entries().iter().find(|&(key, _)| key == "one");
        let expected_one = ("one".to_string(), "1".to_string());
        assert_eq!(Some(&expected_one), actual_one);
        let actual_two = module.entries().iter().find(|&(key, _)| key == "two");
        let expected_two = ("two".to_string(), "2".to_string());
        assert_eq!(Some(&expected_two), actual_two);

        let module = submodules.get(2).unwrap();
        assert_eq!("baz", module.name());
        assert_eq!("\"baz/path\"", module.path().unwrap());
        let actual = module.entries().iter().find(|&(key, _)| key == "flag");
        let expected = ("flag".to_string(), "true".to_string());
        assert_eq!(Some(&expected), actual);
    }
}