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    use std::cmp::Ordering;
    use std::result;

    use ucd_util::{self, PropertyValues};

    use hir;
    use unicode_tables::age;
    use unicode_tables::case_folding_simple::CASE_FOLDING_SIMPLE;
    use unicode_tables::general_category;
    use unicode_tables::grapheme_cluster_break;
    use unicode_tables::property_bool;
    use unicode_tables::property_names::PROPERTY_NAMES;
    use unicode_tables::property_values::PROPERTY_VALUES;
    use unicode_tables::script;
    use unicode_tables::script_extension;
    use unicode_tables::sentence_break;
    use unicode_tables::word_break;

    type Result<T> = result::Result<T, Error>;

    /// An error that occurs when dealing with Unicode.
    ///
    /// We don't impl the Error trait here because these always get converted
    /// into other public errors. (This error type isn't exported.)
    #[derive(Debug)]
    pub enum Error {
        PropertyNotFound,
        PropertyValueNotFound,
    }

    /// An iterator over a codepoint's simple case equivalence class.
    #[derive(Debug)]
    pub struct SimpleFoldIter(::std::slice::Iter<'static, char>);

    impl Iterator for SimpleFoldIter {
        type Item = char;

        fn next(&mut self) -> Option<char> {
            self.0.next().map(|c| *c)
        }
    }

    /// Return an iterator over the equivalence class of simple case mappings
    /// for the given codepoint. The equivalence class does not include the
    /// given codepoint.
    ///
    /// If the equivalence class is empty, then this returns the next scalar
    /// value that has a non-empty equivalence class, if it exists. If no such
    /// scalar value exists, then `None` is returned. The point of this behavior
    /// is to permit callers to avoid calling `simple_fold` more than they need
    /// to, since there is some cost to fetching the equivalence class.
    pub fn simple_fold(c: char) -> result::Result<SimpleFoldIter, Option<char>> {
        CASE_FOLDING_SIMPLE
            .binary_search_by_key(&c, |&(c1, _)| c1)
            .map(|i| SimpleFoldIter(CASE_FOLDING_SIMPLE[i].1.iter()))
            .map_err(|i| {
                if i >= CASE_FOLDING_SIMPLE.len() {
                    None
                } else {
                    Some(CASE_FOLDING_SIMPLE[i].0)
                }
            })
    }

    /// Returns true if and only if the given (inclusive) range contains at least
    /// one Unicode scalar value that has a non-empty non-trivial simple case
    /// mapping.
    ///
    /// This function panics if `end < start`.
    pub fn contains_simple_case_mapping(start: char, end: char) -> bool {
        assert!(start <= end);
        CASE_FOLDING_SIMPLE
            .binary_search_by(|&(c, _)| {
                if start <= c && c <= end {
                    Ordering::Equal
                } else if c > end {
                    Ordering::Greater
                } else {
                    Ordering::Less
                }
            }).is_ok()
    }

    /// A query for finding a character class defined by Unicode. This supports
    /// either use of a property name directly, or lookup by property value. The
    /// former generally refers to Binary properties (see UTS#44, Table 8), but
    /// as a special exception (see UTS#18, Section 1.2) both general categories
    /// (an enumeration) and scripts (a catalog) are supported as if each of their
    /// possible values were a binary property.
    ///
    /// In all circumstances, property names and values are normalized and
    /// canonicalized. That is, `GC == gc == GeneralCategory == general_category`.
    ///
    /// The lifetime `'a` refers to the shorter of the lifetimes of property name
    /// and property value.
    #[derive(Debug)]
    pub enum ClassQuery<'a> {
        /// Return a class corresponding to a Unicode binary property, named by
        /// a single letter.
        OneLetter(char),
        /// Return a class corresponding to a Unicode binary property.
        ///
        /// Note that, by special exception (see UTS#18, Section 1.2), both
        /// general category values and script values are permitted here as if
        /// they were a binary property.
        Binary(&'a str),
        /// Return a class corresponding to all codepoints whose property
        /// (identified by `property_name`) corresponds to the given value
        /// (identified by `property_value`).
        ByValue {
            /// A property name.
            property_name: &'a str,
            /// A property value.
            property_value: &'a str,
        },
    }

    impl<'a> ClassQuery<'a> {
        fn canonicalize(&self) -> Result<CanonicalClassQuery> {
            match *self {
                ClassQuery::OneLetter(c) => self.canonical_binary(&c.to_string()),
                ClassQuery::Binary(name) => self.canonical_binary(name),
                ClassQuery::ByValue { property_name, property_value } => {
                    let property_name = normalize(property_name);
                    let property_value = normalize(property_value);

                    let canon_name = match canonical_prop(&property_name) {
                        None => return Err(Error::PropertyNotFound),
                        Some(canon_name) => canon_name,
                    };
                    Ok(match canon_name {
                        "General_Category" => {
                            let canon = match canonical_gencat(&property_value) {
                                None => return Err(Error::PropertyValueNotFound),
                                Some(canon) => canon,
                            };
                            CanonicalClassQuery::GeneralCategory(canon)
                        }
                        "Script" => {
                            let canon = match canonical_script(&property_value) {
                                None => return Err(Error::PropertyValueNotFound),
                                Some(canon) => canon,
                            };
                            CanonicalClassQuery::Script(canon)
                        }
                        _ => {
                            let vals = match property_values(canon_name) {
                                None => return Err(Error::PropertyValueNotFound),
                                Some(vals) => vals,
                            };
                            let canon_val = match canonical_value(
                                vals,
                                &property_value,
                            ) {
                                None => return Err(Error::PropertyValueNotFound),
                                Some(canon_val) => canon_val,
                            };
                            CanonicalClassQuery::ByValue {
                                property_name: canon_name,
                                property_value: canon_val,
                            }
                        }
                    })
                }
            }
        }

        fn canonical_binary(&self, name: &str) -> Result<CanonicalClassQuery> {
            let norm = normalize(name);

            if let Some(canon) = canonical_prop(&norm) {
                return Ok(CanonicalClassQuery::Binary(canon));
            }
            if let Some(canon) = canonical_gencat(&norm) {
                return Ok(CanonicalClassQuery::GeneralCategory(canon));
            }
            if let Some(canon) = canonical_script(&norm) {
                return Ok(CanonicalClassQuery::Script(canon));
            }
            Err(Error::PropertyNotFound)
        }
    }

    /// Like ClassQuery, but its parameters have been canonicalized. This also
    /// differentiates binary properties from flattened general categories and
    /// scripts.
    #[derive(Debug, Eq, PartialEq)]
    enum CanonicalClassQuery {
        /// The canonical binary property name.
        Binary(&'static str),
        /// The canonical general category name.
        GeneralCategory(&'static str),
        /// The canonical script name.
        Script(&'static str),
        /// An arbitrary association between property and value, both of which
        /// have been canonicalized.
        ///
        /// Note that by construction, the property name of ByValue will never
        /// be General_Category or Script. Those two cases are subsumed by the
        /// eponymous variants.
        ByValue {
            /// The canonical property name.
            property_name: &'static str,
            /// The canonical property value.
            property_value: &'static str,
        },
    }

    /// Looks up a Unicode class given a query. If one doesn't exist, then
    /// `None` is returned.
    pub fn class<'a>(query: ClassQuery<'a>) -> Result<hir::ClassUnicode> {
        use self::CanonicalClassQuery::*;

        match query.canonicalize()? {
            Binary(name) => {
                property_set(property_bool::BY_NAME, name)
                    .map(hir_class)
                    .ok_or(Error::PropertyNotFound)
            }
            GeneralCategory("Any") => {
                Ok(hir_class(&[('\0', '\u{10FFFF}')]))
            }
            GeneralCategory("Assigned") => {
                let mut cls =
                    property_set(general_category::BY_NAME, "Unassigned")
                        .map(hir_class)
                        .ok_or(Error::PropertyNotFound)?;
                cls.negate();
                Ok(cls)
            }
            GeneralCategory("ASCII") => {
                Ok(hir_class(&[('\0', '\x7F')]))
            }
            GeneralCategory(name) => {
                property_set(general_category::BY_NAME, name)
                    .map(hir_class)
                    .ok_or(Error::PropertyValueNotFound)
            }
            Script(name) => {
                property_set(script::BY_NAME, name)
                    .map(hir_class)
                    .ok_or(Error::PropertyValueNotFound)
            }
            ByValue { property_name: "Age", property_value } => {
                let mut class = hir::ClassUnicode::empty();
                for set in ages(property_value)? {
                    class.union(&hir_class(set));
                }
                Ok(class)
            }
            ByValue { property_name: "Script_Extensions", property_value } => {
                property_set(script_extension::BY_NAME, property_value)
                    .map(hir_class)
                    .ok_or(Error::PropertyValueNotFound)
            }
            ByValue { property_name: "Grapheme_Cluster_Break", property_value } => {
                property_set(grapheme_cluster_break::BY_NAME, property_value)
                    .map(hir_class)
                    .ok_or(Error::PropertyValueNotFound)
            }
            ByValue { property_name: "Sentence_Break", property_value } => {
                property_set(sentence_break::BY_NAME, property_value)
                    .map(hir_class)
                    .ok_or(Error::PropertyValueNotFound)
            }
            ByValue { property_name: "Word_Break", property_value } => {
                property_set(word_break::BY_NAME, property_value)
                    .map(hir_class)
                    .ok_or(Error::PropertyValueNotFound)
            }
            _ => {
                // What else should we support?
                Err(Error::PropertyNotFound)
            }
        }
    }

    /// Build a Unicode HIR class from a sequence of Unicode scalar value ranges.
    pub fn hir_class(ranges: &[(char, char)]) -> hir::ClassUnicode {
        let hir_ranges: Vec<hir::ClassUnicodeRange> = ranges
            .iter()
            .map(|&(s, e)| hir::ClassUnicodeRange::new(s, e))
            .collect();
        hir::ClassUnicode::new(hir_ranges)
    }

    fn canonical_prop(normalized_name: &str) -> Option<&'static str> {
        ucd_util::canonical_property_name(PROPERTY_NAMES, normalized_name)
    }

    fn canonical_gencat(normalized_value: &str) -> Option<&'static str> {
        match normalized_value {
            "any" => Some("Any"),
            "assigned" => Some("Assigned"),
            "ascii" => Some("ASCII"),
            _ => {
                let gencats = property_values("General_Category").unwrap();
                canonical_value(gencats, normalized_value)
            }
        }
    }

    fn canonical_script(normalized_value: &str) -> Option<&'static str> {
        let scripts = property_values("Script").unwrap();
        canonical_value(scripts, normalized_value)
    }

    fn canonical_value(
        vals: PropertyValues,
        normalized_value: &str,
    ) -> Option<&'static str> {
        ucd_util::canonical_property_value(vals, normalized_value)
    }

    fn normalize(x: &str) -> String {
        let mut x = x.to_string();
        ucd_util::symbolic_name_normalize(&mut x);
        x
    }

    fn property_values(
        canonical_property_name: &'static str,
    ) -> Option<PropertyValues>
    {
        ucd_util::property_values(PROPERTY_VALUES, canonical_property_name)
    }

    fn property_set(
        name_map: &'static [(&'static str, &'static [(char, char)])],
        canonical: &'static str,
    ) -> Option<&'static [(char, char)]> {
        name_map
            .binary_search_by_key(&canonical, |x| x.0)
            .ok()
            .map(|i| name_map[i].1)
    }

    /// An iterator over Unicode Age sets. Each item corresponds to a set of
    /// codepoints that were added in a particular revision of Unicode. The
    /// iterator yields items in chronological order.
    #[derive(Debug)]
    struct AgeIter {
        ages: &'static [(&'static str, &'static [(char, char)])],
    }

    fn ages(canonical_age: &str) -> Result<AgeIter> {
        const AGES: &'static [(&'static str, &'static [(char, char)])] = &[
            ("V1_1", age::V1_1),
            ("V2_0", age::V2_0),
            ("V2_1", age::V2_1),
            ("V3_0", age::V3_0),
            ("V3_1", age::V3_1),
            ("V3_2", age::V3_2),
            ("V4_0", age::V4_0),
            ("V4_1", age::V4_1),
            ("V5_0", age::V5_0),
            ("V5_1", age::V5_1),
            ("V5_2", age::V5_2),
            ("V6_0", age::V6_0),
            ("V6_1", age::V6_1),
            ("V6_2", age::V6_2),
            ("V6_3", age::V6_3),
            ("V7_0", age::V7_0),
            ("V8_0", age::V8_0),
            ("V9_0", age::V9_0),
            ("V10_0", age::V10_0),
            ("V11_0", age::V11_0),
            ("V12_0", age::V12_0),
            ("V12_1", age::V12_1),
        ];
        assert_eq!(AGES.len(), age::BY_NAME.len(), "ages are out of sync");

        let pos = AGES.iter().position(|&(age, _)| canonical_age == age);
        match pos {
            None => Err(Error::PropertyValueNotFound),
            Some(i) => Ok(AgeIter { ages: &AGES[..i+1] }),
        }
    }

    impl Iterator for AgeIter {
        type Item = &'static [(char, char)];

        fn next(&mut self) -> Option<&'static [(char, char)]> {
            if self.ages.is_empty() {
                None
            } else {
                let set = self.ages[0];
                self.ages = &self.ages[1..];
                Some(set.1)
            }
        }
    }

    #[cfg(test)]
    mod tests {
        use super::{contains_simple_case_mapping, simple_fold};

        #[test]
        fn simple_fold_k() {
            let xs: Vec<char> = simple_fold('k').unwrap().collect();
            assert_eq!(xs, vec!['K', 'K']);

            let xs: Vec<char> = simple_fold('K').unwrap().collect();
            assert_eq!(xs, vec!['k', 'K']);

            let xs: Vec<char> = simple_fold('K').unwrap().collect();
            assert_eq!(xs, vec!['K', 'k']);
        }

        #[test]
        fn simple_fold_a() {
            let xs: Vec<char> = simple_fold('a').unwrap().collect();
            assert_eq!(xs, vec!['A']);

            let xs: Vec<char> = simple_fold('A').unwrap().collect();
            assert_eq!(xs, vec!['a']);
        }

        #[test]
        fn simple_fold_empty() {
            assert_eq!(Some('A'), simple_fold('?').unwrap_err());
            assert_eq!(Some('A'), simple_fold('@').unwrap_err());
            assert_eq!(Some('a'), simple_fold('[').unwrap_err());
            assert_eq!(Some('Ⰰ'), simple_fold('☃').unwrap_err());
        }

        #[test]
        fn simple_fold_max() {
            assert_eq!(None, simple_fold('\u{10FFFE}').unwrap_err());
            assert_eq!(None, simple_fold('\u{10FFFF}').unwrap_err());
        }

        #[test]
        fn range_contains() {
            assert!(contains_simple_case_mapping('A', 'A'));
            assert!(contains_simple_case_mapping('Z', 'Z'));
            assert!(contains_simple_case_mapping('A', 'Z'));
            assert!(contains_simple_case_mapping('@', 'A'));
            assert!(contains_simple_case_mapping('Z', '['));
            assert!(contains_simple_case_mapping('☃', 'Ⰰ'));

            assert!(!contains_simple_case_mapping('[', '['));
            assert!(!contains_simple_case_mapping('[', '`'));

            assert!(!contains_simple_case_mapping('☃', '☃'));
        }

        #[test]
        fn regression_466() {
            use super::{CanonicalClassQuery, ClassQuery};

            let q = ClassQuery::OneLetter('C');
            assert_eq!(
                q.canonicalize().unwrap(),
                CanonicalClassQuery::GeneralCategory("Other"));
        }
    }

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