use crate::{Comparator, Op, Version, VersionReq};

pub(crate) fn matches_req(req: &VersionReq, ver: &Version) -> bool {
    for cmp in &req.comparators {
        if !matches_impl(cmp, ver) {
            return false;
        }
    }

    if ver.pre.is_empty() {
        return true;
    }

    // If a version has a prerelease tag (for example, 1.2.3-alpha.3) then it
    // will only be allowed to satisfy req if at least one comparator with the
    // same major.minor.patch also has a prerelease tag.
    for cmp in &req.comparators {
        if pre_is_compatible(cmp, ver) {
            return true;
        }
    }

    false
}

pub(crate) fn matches_comparator(cmp: &Comparator, ver: &Version) -> bool {
    matches_impl(cmp, ver) && (ver.pre.is_empty() || pre_is_compatible(cmp, ver))
}

fn matches_impl(cmp: &Comparator, ver: &Version) -> bool {
    match cmp.op {
        Op::Exact | Op::Wildcard => matches_exact(cmp, ver),
        Op::Greater => matches_greater(cmp, ver),
        Op::GreaterEq => matches_exact(cmp, ver) || matches_greater(cmp, ver),
        Op::Less => matches_less(cmp, ver),
        Op::LessEq => matches_exact(cmp, ver) || matches_less(cmp, ver),
        Op::Tilde => matches_tilde(cmp, ver),
        Op::Caret => matches_caret(cmp, ver),
        #[cfg(no_non_exhaustive)]
        Op::__NonExhaustive => unreachable!(),
    }
}

fn matches_exact(cmp: &Comparator, ver: &Version) -> bool {
    if ver.major != cmp.major {
        return false;
    }

    if let Some(minor) = cmp.minor {
        if ver.minor != minor {
            return false;
        }
    }

    if let Some(patch) = cmp.patch {
        if ver.patch != patch {
            return false;
        }
    }

    ver.pre == cmp.pre
}

fn matches_greater(cmp: &Comparator, ver: &Version) -> bool {
    if ver.major != cmp.major {
        return ver.major > cmp.major;
    }

    match cmp.minor {
        None => return false,
        Some(minor) => {
            if ver.minor != minor {
                return ver.minor > minor;
            }
        }
    }

    match cmp.patch {
        None => return false,
        Some(patch) => {
            if ver.patch != patch {
                return ver.patch > patch;
            }
        }
    }

    ver.pre > cmp.pre
}

fn matches_less(cmp: &Comparator, ver: &Version) -> bool {
    if ver.major != cmp.major {
        return ver.major < cmp.major;
    }

    match cmp.minor {
        None => return false,
        Some(minor) => {
            if ver.minor != minor {
                return ver.minor < minor;
            }
        }
    }

    match cmp.patch {
        None => return false,
        Some(patch) => {
            if ver.patch != patch {
                return ver.patch < patch;
            }
        }
    }

    ver.pre < cmp.pre
}

fn matches_tilde(cmp: &Comparator, ver: &Version) -> bool {
    if ver.major != cmp.major {
        return false;
    }

    if let Some(minor) = cmp.minor {
        if ver.minor != minor {
            return false;
        }
    }

    if let Some(patch) = cmp.patch {
        if ver.patch != patch {
            return ver.patch > patch;
        }
    }

    ver.pre >= cmp.pre
}

fn matches_caret(cmp: &Comparator, ver: &Version) -> bool {
    if ver.major != cmp.major {
        return false;
    }

    let minor = match cmp.minor {
        None => return true,
        Some(minor) => minor,
    };

    let patch = match cmp.patch {
        None => {
            if cmp.major > 0 {
                return ver.minor >= minor;
            } else {
                return ver.minor == minor;
            }
        }
        Some(patch) => patch,
    };

    if cmp.major > 0 {
        if ver.minor != minor {
            return ver.minor > minor;
        } else if ver.patch != patch {
            return ver.patch > patch;
        }
    } else if minor > 0 {
        if ver.minor != minor {
            return false;
        } else if ver.patch != patch {
            return ver.patch > patch;
        }
    } else if ver.minor != minor || ver.patch != patch {
        return false;
    }

    ver.pre >= cmp.pre
}

fn pre_is_compatible(cmp: &Comparator, ver: &Version) -> bool {
    cmp.major == ver.major
        && cmp.minor == Some(ver.minor)
        && cmp.patch == Some(ver.patch)
        && !cmp.pre.is_empty()
}