// Copyright 2017 Google Inc.
//
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file or at
// https://opensource.org/licenses/MIT.

//! find's permission matching uses a very unix-centric approach, that would
//! be tricky to both implement and use on a windows platform. So we don't
//! even try.

use std::error::Error;
use std::io::{stderr, Write};
#[cfg(unix)]
use uucore::mode::{parse_numeric, parse_symbolic};

use super::{Matcher, MatcherIO, WalkEntry};

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
#[cfg(unix)]
pub enum ComparisonType {
    /// mode bits have to match exactly
    Exact,
    /// all specified mode bits must be set. Others can be as well
    AtLeast,
    /// at least one of the specified bits must be set (or if no bits are
    /// specified then any mode will match)
    AnyOf,
}

#[cfg(unix)]
impl ComparisonType {
    fn mode_bits_match(self, pattern: u32, value: u32) -> bool {
        match self {
            ComparisonType::Exact => (0o7777 & value) == pattern,
            ComparisonType::AtLeast => (value & pattern) == pattern,
            ComparisonType::AnyOf => pattern == 0 || (value & pattern) > 0,
        }
    }
}

#[cfg(unix)]
mod parsing {
    use super::{parse_numeric, parse_symbolic, ComparisonType, Error};

    pub fn split_comparison_type(pattern: &str) -> (ComparisonType, &str) {
        let mut chars = pattern.chars();

        match chars.next() {
            Some('-') => (ComparisonType::AtLeast, chars.as_str()),
            Some('/') => (ComparisonType::AnyOf, chars.as_str()),
            _ => (ComparisonType::Exact, pattern),
        }
    }

    pub fn parse_mode(pattern: &str, for_dir: bool) -> Result<u32, Box<dyn Error>> {
        let mode = if pattern.contains(|c: char| c.is_ascii_digit()) {
            parse_numeric(0, pattern, for_dir)?
        } else {
            let mut mode = 0;
            for chunk in pattern.split(',') {
                mode = parse_symbolic(mode, chunk, 0, for_dir)?;
            }
            mode
        };
        Ok(mode)
    }
}

#[cfg(unix)]
#[derive(Debug)]
pub struct PermMatcher {
    comparison_type: ComparisonType,
    file_pattern: u32,
    dir_pattern: u32,
}

#[cfg(not(unix))]
pub struct PermMatcher {}

impl PermMatcher {
    #[cfg(unix)]
    pub fn new(pattern: &str) -> Result<Self, Box<dyn Error>> {
        let (comparison_type, pattern) = parsing::split_comparison_type(pattern);
        let file_pattern = parsing::parse_mode(pattern, false)?;
        let dir_pattern = parsing::parse_mode(pattern, false)?;
        Ok(Self {
            comparison_type,
            file_pattern,
            dir_pattern,
        })
    }

    #[cfg(not(unix))]
    pub fn new(_dummy_pattern: &str) -> Result<PermMatcher, Box<dyn Error>> {
        Err(From::from(
            "Permission matching is not available on this platform",
        ))
    }
}

impl Matcher for PermMatcher {
    #[cfg(unix)]
    fn matches(&self, file_info: &WalkEntry, _: &mut MatcherIO) -> bool {
        use std::os::unix::fs::PermissionsExt;
        match file_info.metadata() {
            Ok(metadata) => {
                let pattern = if metadata.is_dir() {
                    self.dir_pattern
                } else {
                    self.file_pattern
                };
                self.comparison_type
                    .mode_bits_match(pattern, metadata.permissions().mode())
            }
            Err(e) => {
                writeln!(
                    &mut stderr(),
                    "Error getting permissions for {}: {}",
                    file_info.path().to_string_lossy(),
                    e
                )
                .unwrap();
                false
            }
        }
    }

    #[cfg(not(unix))]
    fn matches(&self, _dummy_file_info: &WalkEntry, _: &mut MatcherIO) -> bool {
        writeln!(
            &mut stderr(),
            "Permission matching not available on this platform!"
        )
        .unwrap();
        return false;
    }
}

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

    use crate::find::matchers::tests::get_dir_entry_for;
    use crate::find::tests::FakeDependencies;

    #[track_caller]
    fn assert_parse(pattern: &str, comparison_type: ComparisonType, mode: u32) {
        let matcher = PermMatcher::new(pattern).unwrap();
        assert_eq!(matcher.comparison_type, comparison_type);
        assert_eq!(matcher.file_pattern, mode);
        assert_eq!(matcher.dir_pattern, mode);
    }

    #[test]
    fn parsing_prefix() {
        assert_parse("u=rwx", Exact, 0o700);
        assert_parse("-u=rwx", AtLeast, 0o700);
        assert_parse("/u=rwx", AnyOf, 0o700);

        assert_parse("700", Exact, 0o700);
        assert_parse("-700", AtLeast, 0o700);
        assert_parse("/700", AnyOf, 0o700);
    }

    #[test]
    fn parsing_octal() {
        assert_parse("/1", AnyOf, 0o001);
        assert_parse("/7777", AnyOf, 0o7777);
    }

    #[test]
    fn parsing_human_readable_individual_bits() {
        assert_parse("/u=r", AnyOf, 0o400);
        assert_parse("/u=w", AnyOf, 0o200);
        assert_parse("/u=x", AnyOf, 0o100);

        assert_parse("/g=r", AnyOf, 0o040);
        assert_parse("/g=w", AnyOf, 0o020);
        assert_parse("/g=x", AnyOf, 0o010);

        assert_parse("/o+r", AnyOf, 0o004);
        assert_parse("/o+w", AnyOf, 0o002);
        assert_parse("/o+x", AnyOf, 0o001);

        assert_parse("/a+r", AnyOf, 0o444);
        assert_parse("/a+w", AnyOf, 0o222);
        assert_parse("/a+x", AnyOf, 0o111);
    }

    #[test]
    fn parsing_human_readable_multiple_bits() {
        assert_parse("/u=rwx", AnyOf, 0o700);
        assert_parse("/a=rwx", AnyOf, 0o777);
    }

    #[test]
    fn parsing_human_readable_multiple_categories() {
        assert_parse("/u=rwx,g=rx,o+r", AnyOf, 0o754);
        assert_parse("/u=rwx,g=rx,o+r,a+w", AnyOf, 0o776);
        assert_parse("/ug=rwx,o+r", AnyOf, 0o774);
    }

    #[test]
    fn parsing_human_readable_set_id_bits() {
        assert_parse("/u=s", AnyOf, 0o4000);
        assert_parse("/g=s", AnyOf, 0o2000);
        assert_parse("/ug=s", AnyOf, 0o6000);
        assert_parse("/o=s", AnyOf, 0o0000);
    }

    #[test]
    fn parsing_human_readable_sticky_bit() {
        assert_parse("/o=t", AnyOf, 0o1000);
    }

    #[test]
    fn parsing_fails() {
        PermMatcher::new("urwx,g=rx,o+r").expect_err("missing equals should fail");
        PermMatcher::new("d=rwx,g=rx,o+r").expect_err("invalid category should fail");
        PermMatcher::new("u=dwx,g=rx,o+r").expect_err("invalid permission bit should fail");
        PermMatcher::new("u_rwx,g=rx,o+r")
            .expect_err("invalid category/permission separator should fail");
        PermMatcher::new("77777777777777").expect_err("overflowing octal value should fail");

        // FIXME: uucore::mode shouldn't accept this
        // PermMatcher::new("u=rwxg=rx,o+r")
        //     .expect_err("missing comma should fail");
    }

    #[test]
    fn comparison_type_matching() {
        let c = ComparisonType::Exact;
        assert!(
            c.mode_bits_match(0, 0),
            "Exact: only 0 should match if pattern is 0"
        );
        assert!(
            !c.mode_bits_match(0, 0o444),
            "Exact: only 0 should match if pattern is 0"
        );
        assert!(
            c.mode_bits_match(0o444, 0o444),
            "Exact: identical bits should match"
        );
        assert!(
            !c.mode_bits_match(0o444, 0o777),
            "Exact: non-identical bits should fail"
        );
        assert!(
            c.mode_bits_match(0o444, 0o70444),
            "Exact:high-end bits should be ignored"
        );

        let c = ComparisonType::AtLeast;
        assert!(
            c.mode_bits_match(0, 0),
            "AtLeast: anything should match if pattern is 0"
        );
        assert!(
            c.mode_bits_match(0, 0o444),
            "AtLeast: anything should match if pattern is 0"
        );
        assert!(
            c.mode_bits_match(0o444, 0o777),
            "AtLeast: identical bits should match"
        );
        assert!(
            c.mode_bits_match(0o444, 0o777),
            "AtLeast: extra bits should match"
        );
        assert!(
            !c.mode_bits_match(0o444, 0o700),
            "AtLeast: missing bits should fail"
        );
        assert!(
            c.mode_bits_match(0o444, 0o70444),
            "AtLeast: high-end bits should be ignored"
        );

        let c = ComparisonType::AnyOf;
        assert!(
            c.mode_bits_match(0, 0),
            "AnyOf: anything should match if pattern is 0"
        );
        assert!(
            c.mode_bits_match(0, 0o444),
            "AnyOf: anything should match if pattern is 0"
        );
        assert!(
            c.mode_bits_match(0o444, 0o777),
            "AnyOf: identical bits should match"
        );
        assert!(
            c.mode_bits_match(0o444, 0o777),
            "AnyOf: extra bits should match"
        );
        assert!(
            c.mode_bits_match(0o777, 0o001),
            "AnyOf: anything should match as long as it has one bit in common"
        );
        assert!(
            !c.mode_bits_match(0o010, 0o001),
            "AnyOf: no matching bits shouldn't match"
        );
        assert!(
            c.mode_bits_match(0o444, 0o70444),
            "AnyOf: high-end bits should be ignored"
        );
    }

    #[test]
    fn perm_matches() {
        let file_info = get_dir_entry_for("test_data/simple", "abbbc");
        let deps = FakeDependencies::new();

        let matcher = PermMatcher::new("-u+r").unwrap();
        assert!(
            matcher.matches(&file_info, &mut deps.new_matcher_io()),
            "user-readable pattern should match file"
        );

        let matcher = PermMatcher::new("-u+x").unwrap();
        assert!(
            !matcher.matches(&file_info, &mut deps.new_matcher_io()),
            "user-executable pattern should not match file"
        );
    }
}
