// This file is part of bsv.
//
// bsv is free software: you can redistribute it and/or modify it under the
// terms of the GNU Affero General Public License as published by the Free
// Software Foundation, either version 3 of the License, or (at your option)
// any later version.
//
// bsv is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
// FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public License for
// more details.
//
// You should have received a copy of the Affero GNU General Public License
// along with bsv.  If not, see <https://www.gnu.org/licenses/>.


use camino::{Utf8Path, Utf8PathBuf};
use regex::RegexSet;

use cas_core::{err, Error, Result};


#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Action {
    Ignore,
    Accept,
}


#[derive(Debug)]
pub struct IgnoreRules {
    patterns: RegexSet,
    actions: Vec<Action>,
}


impl IgnoreRules {
    pub fn new() -> Self {
        Self {
            patterns: RegexSet::new(&[] as &[&str]).unwrap(),
            actions: vec![],
        }
    }

    pub fn from_source<P: AsRef<Utf8Path>>(source: &str, root: P) -> Result<Self> {
        assert!(root.as_ref().is_absolute());

        let separator = if std::path::MAIN_SEPARATOR == '/' {
            "/"
        }
        else {
            assert_eq!(std::path::MAIN_SEPARATOR, '\\');
            "\\\\"
        };

        let mut patterns = Vec::<String>::default();
        let mut actions = Vec::<Action>::default();

        for line in source.lines() {
            let rule = line.trim();
            let mut rule_it = rule.chars().peekable();
            if rule_it.peek().is_none() || rule_it.peek() == Some(&'#') {
                continue;
            }

            if rule_it.peek() == Some(&'!') {
                rule_it.next();
                actions.push(Action::Accept);
            }
            else {
                actions.push(Action::Ignore);
            }

            let mut pat = String::new();
            let mut last_is_sep = false;

            if rule_it.peek() == Some(&'/') {
                pat.push_str("^");
                pat.push_str(&regex::escape(root.as_ref().as_str()));
            }

            while let Some(c) = rule_it.next() {
                if c == '/' {
                    pat.push_str(separator);
                    last_is_sep = true;
                    continue;
                }
                else if c == '*' {
                    if rule_it.peek() == Some(&'*') {
                        rule_it.next();
                        if !last_is_sep || (!rule_it.peek().is_none() && rule_it.peek() != Some(&'/')) {
                            return err!("** pattern can only be used as a whole path segment");
                        }
                        pat.push_str(".*");
                    }
                    else {
                        pat.push_str("[^/]*");
                    }
                }
                else if c == '\\' {
                    let c2 = rule_it.next().ok_or(Error::unknown("invalid \\ at end of rule"))?;
                    let mut buf = [0u8; 4];
                    pat.push_str(&regex::escape(c2.encode_utf8(&mut buf)));
                }
                else {
                    let mut buf = [0u8; 4];
                    pat.push_str(&regex::escape(c.encode_utf8(&mut buf)));
                }
                last_is_sep = false;
            }

            if last_is_sep {
                pat.pop();
            }
            pat.push_str("(/.*)?$");

            dbg!(&pat);
            patterns.push(pat);
        }

        Ok(Self {
            patterns: RegexSet::new(patterns)
                .or_else(|err| err!("failed to compile ignore rules: {err}"))?,
            actions: actions,
        })
    }

    pub fn action_for<P: AsRef<Utf8Path>>(&self, path: P) -> Action {
        assert!(path.as_ref().is_absolute());
        let index = self.patterns.matches(path.as_ref().as_str())
            .iter()
            .next()
            .unwrap_or(self.actions.len());
        *self.actions.get(index).unwrap_or(&Action::Accept)
    }
}



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

    #[test]
    fn test_path_map() {
        let root = Utf8PathBuf::from("/foo.dir/bar");
        let patterns = "!hello/world\nhello\n/world/\n\\!\\*\n*.bak";
        let ignore = IgnoreRules::from_source(patterns, root).unwrap();

        assert_eq!(ignore.action_for(Utf8PathBuf::from("/foo.dir/bar/test")), Action::Accept);
        assert_eq!(ignore.action_for(Utf8PathBuf::from("/foo.dir/bar/test/hello/aoeu")), Action::Ignore);
        assert_eq!(ignore.action_for(Utf8PathBuf::from("/foo.dir/bar/test/hello_world/aoeu")), Action::Accept);
        assert_eq!(ignore.action_for(Utf8PathBuf::from("/foo.dir/bar/test/world/aoeu")), Action::Accept);
        assert_eq!(ignore.action_for(Utf8PathBuf::from("/foo.dir/bar/test/hello/world/aoeu")), Action::Accept);
        assert_eq!(ignore.action_for(Utf8PathBuf::from("/foo.dir/bar/world/aoeu")), Action::Ignore);
        assert_eq!(ignore.action_for(Utf8PathBuf::from("/foo.dir/bar/world")), Action::Ignore);
        assert_eq!(ignore.action_for(Utf8PathBuf::from("/fooXdir/bar/world")), Action::Accept);
        assert_eq!(ignore.action_for(Utf8PathBuf::from("/foo.dir/bar/test/!*/aoeu")), Action::Ignore);
        assert_eq!(ignore.action_for(Utf8PathBuf::from("/foo.dir/bar/test/file.bak")), Action::Ignore);
        assert_eq!(ignore.action_for(Utf8PathBuf::from("/foo.dir/bar/test/fileXbak")), Action::Accept);
        assert_eq!(ignore.action_for(Utf8PathBuf::from("/foo.dir/bar/test.bak/file")), Action::Ignore);
    }
}