//! The `grok` library allows you to quickly parse and match potentially unstructured data
//! into a structed result. It is especially helpful when parsing logfiles of all kinds. This
//! [Rust](http://rust-lang.org) version is mainly a port from the
//! [java version](https://github.com/thekrakken/java-grok)
//! which in drew inspiration from the original
//! [ruby version](https://github.com/logstash-plugins/logstash-filter-grok).
#![doc(html_root_url = "https://docs.rs/grok/1.0.0")]
extern crate onig;

include!(concat!(env!("OUT_DIR"), "/patterns.rs"));

use onig::{Captures, Regex};
use std::collections::{BTreeMap, HashMap};
use std::fmt;
use std::error::Error as StdError;
use std::collections::hash_map::Iter as MapIter;
use std::iter::FromIterator;

const MAX_RECURSION: usize = 1024;

const GROK_PATTERN: &str = r"%\{(?<name>(?<pattern>[A-z0-9]+)(?::(?<alias>[A-z0-9_:;\/\s\.]+))?)(?:=(?<definition>(?:(?:[^{}]+|\.+)+)+))?\}";
const NAME_INDEX: usize = 1;
const PATTERN_INDEX: usize = 2;
const ALIAS_INDEX: usize = 3;
const DEFINITION_INDEX: usize = 4;

/// The `Matches` represent matched results from a `Pattern` against text.
#[derive(Debug)]
pub struct Matches<'a> {
    captures: Captures<'a>,
    names: &'a HashMap<String, u32>,
}

impl<'a> Matches<'a> {
    /// Instantiates the matches for a pattern after the match.
    pub fn new(captures: Captures<'a>, names: &'a HashMap<String, u32>) -> Self {
        Matches { captures, names }
    }

    /// Gets the value for the name (or) alias if found, `None` otherwise.
    pub fn get(&self, name_or_alias: &str) -> Option<&str> {
        match self.names.get(name_or_alias) {
            Some(found) => self.captures.at(*found as usize),
            None => None,
        }
    }

    /// Returns the number of matches.
    pub fn len(&self) -> usize {
        self.captures.len() - 1
    }

    /// Returns true if there are no matches, false otherwise.
    pub fn is_empty(&self) -> bool {
        self.len() == 0
    }

    /// Returns a tuple of key/value with all the matches found.
    ///
    /// Note that if no match is found, the value is empty.
    pub fn iter(&'a self) -> MatchesIter<'a> {
        MatchesIter {
            captures: &self.captures,
            names: self.names.iter(),
        }
    }
}

pub struct MatchesIter<'a> {
    captures: &'a Captures<'a>,
    names: MapIter<'a, String, u32>,
}

impl<'a> Iterator for MatchesIter<'a> {
    type Item = (&'a str, &'a str);

    fn next(&mut self) -> Option<Self::Item> {
        self.names.next().map(|(k, v)| {
            let key = k.as_str();
            let value = match self.captures.at(*v as usize) {
                Some(v) => v,
                None => "",
            };
            (key, value)
        })
    }
}

/// The `Pattern` represents a compiled regex, ready to be matched against arbitrary text.
#[derive(Debug)]
pub struct Pattern {
    regex: Regex,
    names: HashMap<String, u32>,
}

impl Pattern {
    /// Creates a new pattern from a raw regex string and an alias map to identify the
    /// fields properly.
    pub fn new(regex: &str, alias: &HashMap<String, String>) -> Result<Self, Error> {
        match Regex::new(regex) {
            Ok(r) => Ok({
                let names = HashMap::from_iter(r.capture_names().map(|(cap_name, cap_idx)| {
                    let name = match alias.iter().find(|&(_k, v)| *v == cap_name) {
                        Some(item) => item.0.clone(),
                        None => String::from(cap_name),
                    };
                    (name, cap_idx[0])
                }));
                Pattern {
                    regex: r,
                    names: names,
                }
            }),
            Err(_) => Err(Error::RegexCompilationFailed(regex.into())),
        }
    }

    /// Matches this compiled `Pattern` against the text and returns the matches.
    pub fn match_against<'a>(&'a self, text: &'a str) -> Option<Matches<'a>> {
        self.regex
            .captures(text)
            .map(|cap| Matches::new(cap, &self.names))
    }
}

/// The basic structure to manage patterns, entry point for common usage.
#[derive(Debug)]
pub struct Grok {
    definitions: BTreeMap<String, String>,
}

impl Grok {
    /// Creates a new `Grok` instance with no patterns.
    pub fn empty() -> Self {
        Grok {
            definitions: BTreeMap::new(),
        }
    }

    /// Creates a new `Grok` instance and loads all the default patterns.
    pub fn with_patterns() -> Self {
        let mut grok = Grok::empty();
        for &(key, value) in PATTERNS {
            grok.insert_definition(String::from(key), String::from(value));
        }
        grok
    }

    /// Inserts a custom pattern.
    pub fn insert_definition<S: Into<String>>(&mut self, name: S, pattern: S) {
        self.definitions.insert(name.into(), pattern.into());
    }

    /// Compiles the given pattern, making it ready for matching.
    pub fn compile(&mut self, pattern: &str, with_alias_only: bool) -> Result<Pattern, Error> {
        let mut named_regex = String::from(pattern);
        let mut alias: HashMap<String, String> = HashMap::new();

        let mut index = 0;
        let mut iteration_left = MAX_RECURSION;
        let mut continue_iteration = true;

        let grok_regex = match Regex::new(GROK_PATTERN) {
            Ok(r) => r,
            Err(_) => return Err(Error::RegexCompilationFailed(GROK_PATTERN.into())),
        };

        while continue_iteration {
            continue_iteration = false;
            if iteration_left == 0 {
                return Err(Error::RecursionTooDeep);
            }
            iteration_left -= 1;

            if let Some(m) = grok_regex.captures(&named_regex.clone()) {
                continue_iteration = true;
                let raw_pattern = match m.at(PATTERN_INDEX) {
                    Some(p) => p,
                    None => {
                        return Err(Error::GenericCompilationFailure(
                            "Could not find pattern in matches".into(),
                        ))
                    }
                };

                let mut name = match m.at(NAME_INDEX) {
                    Some(n) => String::from(n),
                    None => {
                        return Err(Error::GenericCompilationFailure(
                            "Could not find name in matches".into(),
                        ))
                    }
                };

                if let Some(definition) = m.at(DEFINITION_INDEX) {
                    self.insert_definition(raw_pattern, definition);
                    name = format!("{}={}", name, definition);
                }

                // Since a pattern with a given name can show up more than once, we need to
                // loop through the number of matches found and apply the transformations
                // on each of them.
                for _ in 0..named_regex.matches(&format!("%{{{}}}", name)).count() {
                    // Check if we have a definition for the raw pattern key and fail quickly
                    // if not.
                    let pattern_definition = match self.definitions.get(raw_pattern) {
                        Some(d) => d,
                        None => return Err(Error::DefinitionNotFound(raw_pattern.into())),
                    };

                    // If no alias is specified and all but with alias are ignored,
                    // the replacement tells the regex engine to ignore the matches.
                    // Otherwise, the definition is turned into a regex that the
                    // engine understands and uses a named group.

                    let replacement = if with_alias_only && m.at(ALIAS_INDEX).is_none() {
                        format!("(?:{})", pattern_definition)
                    } else {
                        // If an alias is specified by the user use that one to
                        // match the name<index> conversion, otherwise just use
                        // the name of the pattern definition directly.
                        alias.insert(
                            match m.at(ALIAS_INDEX) {
                                Some(a) => a.into(),
                                None => name.clone(),
                            },
                            format!("name{}", index),
                        );

                        format!("(?<name{}>{})", index, pattern_definition)
                    };

                    // Finally, look for the original %{...} style pattern and
                    // replace it with our replacement (only the first occurrence
                    // since we are iterating one by one).
                    named_regex = named_regex.replacen(&format!("%{{{}}}", name), &replacement, 1);

                    index += 1;
                }
            }
        }

        if named_regex.is_empty() {
            Err(Error::CompiledPatternIsEmpty(pattern.into()))
        } else {
            Pattern::new(&named_regex, &alias)
        }
    }
}

impl Default for Grok {
    fn default() -> Grok {
        Grok::with_patterns()
    }
}

/// An error that occurred when using this library.
#[derive(Clone, Debug, PartialEq)]
pub enum Error {
    /// The recursion while compiling has exhausted the limit.
    RecursionTooDeep,
    /// After compiling, the resulting compiled regex pattern is empty.
    CompiledPatternIsEmpty(String),
    /// A corresponding pattern definition could not be found for the given name.
    DefinitionNotFound(String),
    /// If the compilation for a specific regex in the underlying engine failed.
    RegexCompilationFailed(String),
    /// Something is messed up during the compilation phase.
    GenericCompilationFailure(String),
    /// Hints that destructuring should not be exhaustive.
    ///
    /// This enum may grow additional variants, so this makes sure clients
    /// don't count on exhaustive matching. (Otherwise, adding a new variant
    /// could break existing code.)
    #[doc(hidden)]
    __Nonexhaustive,
}

impl StdError for Error {
    fn description(&self) -> &str {
        match *self {
            Error::RecursionTooDeep => "compilation recursion reached the limit",
            Error::CompiledPatternIsEmpty(_) => "compiled pattern is empty",
            Error::DefinitionNotFound(_) => "pattern definition not found while compiling",
            Error::RegexCompilationFailed(_) => "regex compilation in the engine failed",
            Error::GenericCompilationFailure(_) => {
                "something happened during the compilation phase"
            }
            Error::__Nonexhaustive => unreachable!(),
        }
    }

    fn cause(&self) -> Option<&StdError> {
        None
    }
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Error::RecursionTooDeep => write!(
                f,
                "Recursion while compiling reached the limit of {}",
                MAX_RECURSION
            ),
            Error::CompiledPatternIsEmpty(ref p) => write!(
                f,
                "The given pattern \"{}\" ended up compiling into an empty regex",
                p
            ),
            Error::DefinitionNotFound(ref d) => write!(
                f,
                "The given pattern definition name \"{}\" could not be found in the definition map",
                d
            ),
            Error::RegexCompilationFailed(ref r) => write!(
                f,
                "The given regex \"{}\" failed compilation in the underlying engine",
                r
            ),
            Error::GenericCompilationFailure(ref d) => write!(
                f,
                "Something unexpected happened during the compilation phase: \"{}\"",
                d
            ),
            Error::__Nonexhaustive => unreachable!(),
        }
    }
}

#[cfg(test)]
mod tests {

    use super::*;

    #[test]
    fn test_simple_anonymous_pattern() {
        let mut grok = Grok::empty();
        grok.insert_definition("USERNAME", r"[a-zA-Z0-9._-]+");
        let pattern = grok.compile("%{USERNAME}", false)
            .expect("Error while compiling!");

        let matches = pattern.match_against("root").expect("No matches found!");
        assert_eq!("root", matches.get("USERNAME").unwrap());
        assert_eq!(1, matches.len());
        let matches = pattern
            .match_against("john doe")
            .expect("No matches found!");
        assert_eq!("john", matches.get("USERNAME").unwrap());
        assert_eq!(1, matches.len());
    }

    #[test]
    fn test_simple_named_pattern() {
        let mut grok = Grok::empty();
        grok.insert_definition("USERNAME", r"[a-zA-Z0-9._-]+");
        let pattern = grok.compile("%{USERNAME:usr}", false)
            .expect("Error while compiling!");

        let matches = pattern.match_against("root").expect("No matches found!");
        assert_eq!("root", matches.get("usr").unwrap());
        assert_eq!(1, matches.len());
        let matches = pattern
            .match_against("john doe")
            .expect("No matches found!");
        assert_eq!("john", matches.get("usr").unwrap());
        assert_eq!(1, matches.len());
    }

    #[test]
    fn test_alias_anonymous_pattern() {
        let mut grok = Grok::empty();
        grok.insert_definition("USERNAME", r"[a-zA-Z0-9._-]+");
        grok.insert_definition("USER", r"%{USERNAME}");
        let pattern = grok.compile("%{USER}", false)
            .expect("Error while compiling!");

        let matches = pattern.match_against("root").expect("No matches found!");
        assert_eq!("root", matches.get("USER").unwrap());
        let matches = pattern
            .match_against("john doe")
            .expect("No matches found!");
        assert_eq!("john", matches.get("USER").unwrap());
    }

    #[test]
    fn test_ailas_named_pattern() {
        let mut grok = Grok::empty();
        grok.insert_definition("USERNAME", r"[a-zA-Z0-9._-]+");
        grok.insert_definition("USER", r"%{USERNAME}");
        let pattern = grok.compile("%{USER:usr}", false)
            .expect("Error while compiling!");

        let matches = pattern.match_against("root").expect("No matches found!");
        assert_eq!("root", matches.get("usr").unwrap());
        let matches = pattern
            .match_against("john doe")
            .expect("No matches found!");
        assert_eq!("john", matches.get("usr").unwrap());
    }

    #[test]
    fn test_composite_or_pattern() {
        let mut grok = Grok::empty();
        grok.insert_definition("MAC", r"(?:%{CISCOMAC}|%{WINDOWSMAC}|%{COMMONMAC})");
        grok.insert_definition("CISCOMAC", r"(?:(?:[A-Fa-f0-9]{4}\.){2}[A-Fa-f0-9]{4})");
        grok.insert_definition("WINDOWSMAC", r"(?:(?:[A-Fa-f0-9]{2}-){5}[A-Fa-f0-9]{2})");
        grok.insert_definition("COMMONMAC", r"(?:(?:[A-Fa-f0-9]{2}:){5}[A-Fa-f0-9]{2})");
        let pattern = grok.compile("%{MAC}", false)
            .expect("Error while compiling!");

        let matches = pattern
            .match_against("5E:FF:56:A2:AF:15")
            .expect("No matches found!");
        assert_eq!("5E:FF:56:A2:AF:15", matches.get("MAC").unwrap());
        assert_eq!(4, matches.len());
        let matches = pattern
            .match_against("hello! 5E:FF:56:A2:AF:15 what?")
            .expect("No matches found!");
        assert_eq!("5E:FF:56:A2:AF:15", matches.get("MAC").unwrap());
        assert_eq!(true, pattern.match_against("5E:FF").is_none());
    }

    #[test]
    fn test_multiple_patterns() {
        let mut grok = Grok::empty();
        grok.insert_definition("YEAR", r"(\d\d){1,2}");
        grok.insert_definition("MONTH", r"\b(?:Jan(?:uary)?|Feb(?:ruary)?|Mar(?:ch)?|Apr(?:il)?|May|Jun(?:e)?|Jul(?:y)?|Aug(?:ust)?|Sep(?:tember)?|Oct(?:ober)?|Nov(?:ember)?|Dec(?:ember)?)\b");
        grok.insert_definition("DAY", r"(?:Mon(?:day)?|Tue(?:sday)?|Wed(?:nesday)?|Thu(?:rsday)?|Fri(?:day)?|Sat(?:urday)?|Sun(?:day)?)");
        let pattern = grok.compile("%{DAY} %{MONTH} %{YEAR}", false)
            .expect("Error while compiling!");

        let matches = pattern
            .match_against("Monday March 2012")
            .expect("No matches found!");
        assert_eq!("Monday", matches.get("DAY").unwrap());
        assert_eq!("March", matches.get("MONTH").unwrap());
        assert_eq!("2012", matches.get("YEAR").unwrap());
        assert_eq!(None, matches.get("unknown"));
    }

    #[test]
    fn test_with_alias_only() {
        let mut grok = Grok::empty();
        grok.insert_definition("MAC", r"(?:%{CISCOMAC}|%{WINDOWSMAC}|%{COMMONMAC})");
        grok.insert_definition("CISCOMAC", r"(?:(?:[A-Fa-f0-9]{4}\.){2}[A-Fa-f0-9]{4})");
        grok.insert_definition("WINDOWSMAC", r"(?:(?:[A-Fa-f0-9]{2}-){5}[A-Fa-f0-9]{2})");
        grok.insert_definition("COMMONMAC", r"(?:(?:[A-Fa-f0-9]{2}:){5}[A-Fa-f0-9]{2})");
        let pattern = grok.compile("%{MAC:macaddr}", true)
            .expect("Error while compiling!");

        let matches = pattern
            .match_against("5E:FF:56:A2:AF:15")
            .expect("No matches found!");
        assert_eq!("5E:FF:56:A2:AF:15", matches.get("macaddr").unwrap());
        assert_eq!(1, matches.len());
        let matches = pattern
            .match_against("hello! 5E:FF:56:A2:AF:15 what?")
            .expect("No matches found!");
        assert_eq!("5E:FF:56:A2:AF:15", matches.get("macaddr").unwrap());
        assert_eq!(true, pattern.match_against("5E:FF").is_none());
    }

    #[test]
    fn test_match_iterator() {
        let mut grok = Grok::empty();
        grok.insert_definition("YEAR", r"(\d\d){1,2}");
        grok.insert_definition("MONTH", r"\b(?:Jan(?:uary)?|Feb(?:ruary)?|Mar(?:ch)?|Apr(?:il)?|May|Jun(?:e)?|Jul(?:y)?|Aug(?:ust)?|Sep(?:tember)?|Oct(?:ober)?|Nov(?:ember)?|Dec(?:ember)?)\b");
        grok.insert_definition("DAY", r"(?:Mon(?:day)?|Tue(?:sday)?|Wed(?:nesday)?|Thu(?:rsday)?|Fri(?:day)?|Sat(?:urday)?|Sun(?:day)?)");
        grok.insert_definition("USERNAME", r"[a-zA-Z0-9._-]+");
        grok.insert_definition("SPACE", r"\s*");

        let pattern = grok.compile(
            "%{DAY:day} %{MONTH:month} %{YEAR:year}%{SPACE}%{USERNAME:user}?",
            true,
        ).expect("Error while compiling!");
        let matches = pattern
            .match_against("Monday March 2012")
            .expect("No matches found!");
        let mut found = 0;
        for (k, v) in matches.iter() {
            match k {
                "day" => assert_eq!("Monday", v),
                "month" => assert_eq!("March", v),
                "year" => assert_eq!("2012", v),
                "user" => assert_eq!("", v), // <- optional
                e => panic!(format!("{:?}", e)),
            }
            found += 1;
        }
        assert_eq!(4, found);
    }

    #[test]
    fn test_loaded_default_patterns() {
        let mut grok = Grok::with_patterns();
        let pattern = grok.compile("%{DAY} %{MONTH} %{YEAR}", false)
            .expect("Error while compiling!");

        let matches = pattern
            .match_against("Monday March 2012")
            .expect("No matches found!");
        assert_eq!("Monday", matches.get("DAY").unwrap());
        assert_eq!("March", matches.get("MONTH").unwrap());
        assert_eq!("2012", matches.get("YEAR").unwrap());
        assert_eq!(None, matches.get("unknown"));
    }

    #[test]
    fn test_compilation_of_all_default_patterns() {
        let mut grok = Grok::default();
        let mut num_checked = 0;
        for &(key, _) in PATTERNS {
            let pattern = format!("%{{{}}}", key);
            grok.compile(&pattern, false).expect(&format!(
                "Pattern {} key {} failed to compile!",
                pattern, key
            ));
            num_checked += 1;
        }
        assert!(num_checked > 0);
    }

    #[test]
    fn test_adhoc_pattern() {
        let mut grok = Grok::default();
        let pattern = grok.compile(r"\[(?<threadname>[^\]]+)\]", false)
            .expect("Error while compiling!");

        let matches = pattern
            .match_against("[thread1]")
            .expect("No matches found!");
        assert_eq!("thread1", matches.get("threadname").unwrap());
    }

    #[test]
    fn test_adhoc_pattern_in_iter() {
        let mut grok = Grok::default();
        let pattern = grok.compile(r"\[(?<threadname>[^\]]+)\]", false)
            .expect("Error while compiling!");

        let matches = pattern
            .match_against("[thread1]")
            .expect("No matches found!");
        let mut found = 0;
        for (k, v) in matches.iter() {
            assert_eq!("threadname", k);
            assert_eq!("thread1", v);
            found += 1;
        }
        assert_eq!(1, found);
    }
}