use std::env;
use std::fs::File;
use std::io::prelude::*;
use std::path::Path;
use substring::Substring;
use walkdir::WalkDir;

#[cfg(windows)]
const LINE_ENDING: &'static str = "\r\n";
#[cfg(not(windows))]
const LINE_ENDING: &'static str = "\n";

const CARET: char = '^';

/// Converts the content into a vector of strings, each string separated by the last caret in the file.
// Unfortunately, it doesn't separate comments yet but the get_entry() ignores them, anyway.
fn normalize_entries<S: Into<String>>(content: S) -> Vec<String> {
    let cst_ending = format!("{}{}", CARET, LINE_ENDING);
    let entries = content
        .into()
        .trim_end()
        .trim_end_matches(CARET)
        .split(cst_ending.as_str())
        .map(|s| s.to_string())
        .collect::<Vec<String>>();

    return entries;
}

/// Parses a specific entry from a string.
///
/// # Example
/// ```rust
/// use cst::get_entry;
///
/// let input = "1 ^The quick brown fox jumps over the lazy dog.^";
/// let expect = "The quick brown fox jumps over the lazy dog.";
/// let entry = get_entry(input, 1);
/// assert_eq!(entry.unwrap(), expect);
/// ```
pub fn get_entry<S: Into<String>>(content: S, key: usize) -> Option<String> {
    let entries = normalize_entries(content);

    // Find the entry
    for entry in entries {
        if entry.contains(&key.to_string()) {
            let start_index = entry.find(CARET)?;
            let line = entry.substring(start_index + 1, entry.len());
            return Some(line.to_string());
        }
    }

    // No entry found.
    return None;
}

pub struct UIText {
    language: String,
}

/// The UIText is a wrapper around the get_entry() function that recursively searches directories for a file with the given language and key.
///
/// # Example
/// ```rust
/// use cst::UIText;
///
/// let expect = "The quick brown fox jumps over the lazy dog.";
/// let ui_text = UIText::new("example"); // uitext/example.dir
/// let entry = ui_text.get_text(101, 1); // Entry 1 of _101_[name].cst
///
/// assert_eq!(entry.unwrap(), expect);
/// ```
impl UIText {
    pub fn new<S: Into<String>>(language: S) -> UIText {
        UIText {
            language: language.into(),
        }
    }

    pub fn get_text(&self, id: usize, key: usize) -> Option<String> {
        let language_dir = format!(
            "{}/uitext/{}.dir/",
            env::current_dir().unwrap().display(),
            self.language
        );

        for entry in WalkDir::new(&language_dir)
            .sort_by_file_name()
            .into_iter()
            .filter_map(|e| e.ok())
        {
            let f_name = entry.file_name().to_string_lossy();
            let find_id = format!("_{}_", id);
            if f_name.contains(&find_id) && f_name.ends_with(".cst") {
                let mut open_file =
                    match File::open(Path::new(format!("{}/{}", language_dir, f_name).as_str())) {
                        Err(_) => panic!("couldn't open {}", f_name),
                        Ok(file) => file,
                    };
                let mut contents = String::new();
                match open_file.read_to_string(&mut contents) {
                    Ok(_) => return Some(get_entry(contents, key)?),
                    Err(why) => panic!("couldn't read {}: {}", f_name, why),
                }
            }
        }
        return None;
    }
}

#[cfg(test)]
mod tests {
    use crate::{get_entry, normalize_entries, UIText};

    #[cfg(windows)]
    const LINE_ENDING: &'static str = "\r\n";
    #[cfg(not(windows))]
    const LINE_ENDING: &'static str = "\n";

    #[test]
    fn get_uitext() {
        let ui_text = UIText::new("lorem");
        let expected = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin ac dictum orci, at tincidunt nulla. Donec aliquet, eros non interdum posuere, ipsum sapien molestie nunc, nec facilisis libero ipsum et risus. In sed lorem vel ipsum placerat viverra.".to_string();
        dbg!(ui_text.get_text(101, 1));
        assert_eq!(ui_text.get_text(101, 1).unwrap(), expected);
    }

    #[test]
    fn is_normalized() {
        let example = format!(
            "1 ^The quick brown fox^{}2 ^jumps over the lazy dog^{}",
            LINE_ENDING, LINE_ENDING
        );
        let input = normalize_entries(example);
        let expected = [
            "1 ^The quick brown fox".to_string(),
            "2 ^jumps over the lazy dog".to_string(),
        ];
        assert_eq!(input, expected);
    }

    #[test]
    fn test_entry() {
        let example = format!(
            "# comment{}1 ^The quick brown fox^{}2 ^jumps over the lazy dog^{}",
            LINE_ENDING, LINE_ENDING, LINE_ENDING
        );
        let expected = "jumps over the lazy dog".to_string();
        dbg!(get_entry(&example, 2));
        assert_eq!(get_entry(example, 2).unwrap(), expected);
    }
}