// Copyright 2020 Folyd
// Copyright 1999 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
//!
//! A native Rust port of [Google's robots.txt parser and matcher C++ library](https://github.com/google/robotstxt).
//!
//! - Native Rust port, no third-part crate dependency
//! - Preserves all behaviour of original library
//! - 100% google original test passed
//!
//! # Quick start
//! ```rust
//! use robotstxt::DefaultMatcher;
//!
//! let mut matcher = DefaultMatcher::default();
//! let robots_body = "user-agent: FooBot\n\
//!                    disallow: /\n";
//! assert_eq!(false, matcher.one_agent_allowed_by_robots(robots_body, "FooBot", "https://foo.com/"));
//! ```

use std::borrow::Cow;

use matcher::{LongestMatchRobotsMatchStrategy, RobotsMatcher};
use parser::RobotsTxtParser;

/// A matcher module.
pub mod matcher;
/// A parser module.
pub mod parser;

/// A default [RobotsMatcher] with [LongestMatchRobotsMatchStrategy].
pub type DefaultMatcher<'a> = RobotsMatcher<'a, LongestMatchRobotsMatchStrategy>;

/// Handler for directives found in robots.txt.
pub trait RobotsParseHandler {
    fn handle_robots_start(&mut self);
    fn handle_robots_end(&mut self);
    fn handle_user_agent(&mut self, line_num: u32, user_agent: &str);
    fn handle_allow(&mut self, line_num: u32, value: &str);
    fn handle_disallow(&mut self, line_num: u32, value: &str);
    fn handle_sitemap(&mut self, line_num: u32, value: &str);
    /// Any other unrecognized name/value pairs.
    fn handle_unknown_action(&mut self, line_num: u32, action: &str, value: &str);
}

/// Extracts path (with params) and query part from URL. Removes scheme,
/// authority, and fragment. Result always starts with "/".
/// Returns "/" if the url doesn't have a path or is not valid.
/// ```rust
///use robotstxt::get_path_params_query;
///
///let f= get_path_params_query;
///assert_eq!("/", f(""));
///assert_eq!("/", f("http://www.example.com"));
///assert_eq!("/", f("http://www.example.com/"));
///assert_eq!("/a", f("http://www.example.com/a"));
///assert_eq!("/a/", f("http://www.example.com/a/"));
///assert_eq!(
///    "/a/b?c=http://d.e/",
///    f("http://www.example.com/a/b?c=http://d.e/")
///);
///assert_eq!(
///    "/a/b?c=d&e=f",
///    f("http://www.example.com/a/b?c=d&e=f#fragment")
///);
///assert_eq!("/", f("example.com"));
///assert_eq!("/", f("example.com/"));
///assert_eq!("/a", f("example.com/a"));
///assert_eq!("/a/", f("example.com/a/"));
///assert_eq!("/a/b?c=d&e=f", f("example.com/a/b?c=d&e=f#fragment"));
///assert_eq!("/", f("a"));
///assert_eq!("/", f("a/"));
///assert_eq!("/a", f("/a"));
///assert_eq!("/b", f("a/b"));
///assert_eq!("/?a", f("example.com?a"));
///assert_eq!("/a;b", f("example.com/a;b#c"));
///assert_eq!("/b/c", f("//a/b/c"));
/// ```
pub fn get_path_params_query(url: &str) -> Cow<str> {
    fn find_first_of(s: &str, pattern: &str, start_position: usize) -> Option<usize> {
        s[start_position..]
            .find(|c| pattern.contains(c))
            .map(|pos| pos + start_position)
    }
    fn find(s: &str, pattern: &str, start_position: usize) -> Option<usize> {
        s[start_position..]
            .find(pattern)
            .map(|pos| pos + start_position)
    }

    // Initial two slashes are ignored.
    let search_start = if url.len() >= 2 && url.get(..2) == Some("//") {
        2
    } else {
        0
    };
    let early_path = find_first_of(url, "/?;", search_start);
    let mut protocol_end = find(url, "://", search_start);

    if early_path.is_some() && early_path < protocol_end {
        // If path, param or query starts before ://, :// doesn't indicate protocol.
        protocol_end = None;
    }
    if protocol_end.is_none() {
        protocol_end = Some(search_start);
    } else {
        protocol_end = protocol_end.map(|pos| pos + 3)
    }

    if let Some(path_start) = find_first_of(url, "/?;", protocol_end.unwrap()) {
        let hash_pos = find(url, "#", search_start);
        if hash_pos.is_some() && hash_pos.unwrap() < path_start {
            return Cow::Borrowed("/");
        }

        let path_end = hash_pos.unwrap_or_else(|| url.len());
        if url.get(path_start..=path_start) != Some("/") {
            // Prepend a slash if the result would start e.g. with '?'.
            return Cow::Owned(format!("/{}", &url[path_start..path_end]));
        }
        return Cow::Borrowed(&url[path_start..path_end]);
    }

    Cow::Borrowed("/")
}

/// Parses body of a robots.txt and emits parse callbacks. This will accept
/// typical typos found in robots.txt, such as 'disalow'.
///
/// Note, this function will accept all kind of input but will skip
/// everything that does not look like a robots directive.
pub fn parse_robotstxt(robots_body: &str, parse_callback: &mut impl RobotsParseHandler) {
    let mut parser = RobotsTxtParser::new(robots_body, parse_callback);
    parser.parse();
}

#[cfg(test)]
mod tests {
    #![allow(unused_variables)]

    use super::*;

    #[derive(Default)]
    struct RobotsStatsReporter {
        last_line_seen: u32,
        valid_directives: u32,
        unknown_directives: u32,
        sitemap: String,
    }

    impl RobotsStatsReporter {
        fn digest(&mut self, line_num: u32) {
            assert!(line_num >= self.last_line_seen);
            self.last_line_seen = line_num;
            self.valid_directives += 1;
        }
    }

    impl RobotsParseHandler for RobotsStatsReporter {
        fn handle_robots_start(&mut self) {
            self.last_line_seen = 0;
            self.valid_directives = 0;
            self.unknown_directives = 0;
            self.sitemap.clear();
        }

        fn handle_robots_end(&mut self) {}

        fn handle_user_agent(&mut self, line_num: u32, user_agent: &str) {
            self.digest(line_num);
        }

        fn handle_allow(&mut self, line_num: u32, value: &str) {
            self.digest(line_num);
        }

        fn handle_disallow(&mut self, line_num: u32, value: &str) {
            self.digest(line_num);
        }

        fn handle_sitemap(&mut self, line_num: u32, value: &str) {
            self.digest(line_num);
            self.sitemap.push_str(value);
        }

        // Any other unrecognized name/v pairs.
        fn handle_unknown_action(&mut self, line_num: u32, action: &str, value: &str) {
            self.last_line_seen = line_num;
            self.unknown_directives += 1;
        }
    }

    #[test]
    // Different kinds of line endings are all supported: %x0D / %x0A / %x0D.0A
    fn test_lines_numbers_are_counted_correctly() {
        let mut report = RobotsStatsReporter::default();
        let unix_file = "User-Agent: foo\n\
        Allow: /some/path\n\
        User-Agent: bar\n\
        \n\
        \n\
        Disallow: /\n";
        super::parse_robotstxt(unix_file, &mut report);
        assert_eq!(4, report.valid_directives);
        assert_eq!(6, report.last_line_seen);

        let mac_file = "User-Agent: foo\r\
        Allow: /some/path\r\
        User-Agent: bar\r\
        \r\
        \r\
        Disallow: /\r";
        super::parse_robotstxt(mac_file, &mut report);
        assert_eq!(4, report.valid_directives);
        assert_eq!(6, report.last_line_seen);

        let no_final_new_line = "User-Agent: foo\n\
        Allow: /some/path\n\
        User-Agent: bar\n\
        \n\
        \n\
        Disallow: /";
        super::parse_robotstxt(no_final_new_line, &mut report);
        assert_eq!(4, report.valid_directives);
        assert_eq!(6, report.last_line_seen);

        let mixed_file = "User-Agent: foo\n\
        Allow: /some/path\r\n\
        User-Agent: bar\n\
        \r\n\
        \n\
        Disallow: /";
        super::parse_robotstxt(mixed_file, &mut report);
        assert_eq!(4, report.valid_directives);
        assert_eq!(6, report.last_line_seen);
    }

    #[test]
    // BOM characters are unparseable and thus skipped. The rules following the line
    // are used.
    fn test_utf8_byte_order_mark_is_skipped() {
        let mut report = RobotsStatsReporter::default();
        let utf8_file_full_bom = "\u{EF}\u{BB}\u{BF}\
        User-Agent: foo\n\
        Allow: /AnyValue\n";
        super::parse_robotstxt(utf8_file_full_bom, &mut report);
        assert_eq!(2, report.valid_directives);
        assert_eq!(0, report.unknown_directives);

        // We allow as well partial ByteOrderMarks.
        let utf8_file_partial_2bom = "\u{EF}\u{BB}\
        User-Agent: foo\n\
        Allow: /AnyValue\n";
        super::parse_robotstxt(utf8_file_partial_2bom, &mut report);
        assert_eq!(2, report.valid_directives);
        assert_eq!(0, report.unknown_directives);

        let utf8_file_partial_1bom = "\u{EF}\
        User-Agent: foo\n\
        Allow: /AnyValue\n";
        super::parse_robotstxt(utf8_file_partial_1bom, &mut report);
        assert_eq!(2, report.valid_directives);
        assert_eq!(0, report.unknown_directives);

        // If the BOM is not the right sequence, the first line looks like garbage
        // that is skipped (we essentially see "\x11\xBFUser-Agent").
        let utf8_file_broken_bom = "\u{EF}\u{11}\u{BF}\
        User-Agent: foo\n\
        Allow: /AnyValue\n";
        super::parse_robotstxt(utf8_file_broken_bom, &mut report);
        assert_eq!(1, report.valid_directives);
        // // We get one broken line.
        assert_eq!(1, report.unknown_directives);

        // Some other messed up file: BOMs only valid in the beginning of the file.
        let utf8_bom_somewhere_in_middle_of_file = "User-Agent: foo\n\
        \u{EF}\u{BB}\u{BF}\
        Allow: /AnyValue\n";
        super::parse_robotstxt(utf8_bom_somewhere_in_middle_of_file, &mut report);
        assert_eq!(1, report.valid_directives);
        assert_eq!(1, report.unknown_directives);
    }

    #[test]
    // Google specific: the I-D allows any line that crawlers might need, such as
    // sitemaps, which Google supports.
    // See REP I-D section "Other records".
    // https://tools.ietf.org/html/draft-koster-rep#section-2.2.4
    fn test_non_standard_line_example_sitemap() {
        let mut report = RobotsStatsReporter::default();

        {
            let sitemap_loc = "http://foo.bar/sitemap.xml";
            let mut robotstxt: String = "User-Agent: foo\n\
        Allow: /some/path\n\
        User-Agent: bar\n\
        \n\
        \n"
            .into();
            robotstxt.push_str(&format!("Sitemap: {}\n", sitemap_loc));

            super::parse_robotstxt(&robotstxt, &mut report);
            assert_eq!(sitemap_loc, report.sitemap.as_str());
        }

        {
            // A sitemap line may appear anywhere in the file.
            let mut robotstxt = String::new();
            let sitemap_loc = "http://foo.bar/sitemap.xml";
            let robotstxt_temp = "User-Agent: foo\n\
            Allow: /some/path\n\
            User-Agent: bar\n\
            \n\
            \n";
            robotstxt.push_str(&format!("Sitemap: {}\n{}", sitemap_loc, robotstxt_temp));

            super::parse_robotstxt(&robotstxt, &mut report);
            assert_eq!(sitemap_loc, report.sitemap.as_str());
        }
    }

    #[test]
    fn test_blank_line_case() {
        let robots_content = r#"User-agent: *
Disallow: /*q=
Disallow: /users/*?
Disallow: /join/*?
Disallow: /morelikethis/
Disallow: /download/
Disallow: /checkout/
Disallow: /global/
Disallow: /api/
Disallow: /critiques/
 
Sitemap: http://sitemaps.test.net/sitemap-index.xml.gz"#;
        let mut matcher = DefaultMatcher::default();
        assert!(matcher.one_agent_allowed_by_robots(
            &robots_content,
            "bot",
            "https://www.test.com/"
        ));
    }

    #[test]
    fn test_unknown_robotstxt_case() {
        let robots_content = "#!/usr/bin/env bash\n\
# Make sure you have `curl` installed\n\
\n\
######## VARIABLES #########\n\
abc";
        let mut matcher = DefaultMatcher::default();
        assert!(matcher.one_agent_allowed_by_robots(
            &robots_content,
            "bot",
            "https://www.test.com/"
        ));
    }
}