// This file is part of ICU4X. For terms of use, please see the file

// called LICENSE at the top level of the ICU4X source tree

// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).

//! Types for walking stepwise through a trie.

//!

//! For examples, see the `.cursor()` functions

//! and the `Cursor` types in this module.

use crate::reader;

use crate::ZeroAsciiIgnoreCaseTrie;

use crate::ZeroTrieSimpleAscii;

use core::fmt;

impl<Store> ZeroTrieSimpleAscii<Store>

where

    Store: AsRef<[u8]> + ?Sized,

{

    /// Gets a cursor into the current trie.

    ///

    /// Useful to query a trie with data that is not a slice.

    ///

    /// This is currently supported only on [`ZeroTrieSimpleAscii`]

    /// and [`ZeroAsciiIgnoreCaseTrie`].

    ///

    /// # Examples

    ///

    /// Get a value out of a trie by [writing](fmt::Write) it to the cursor:

    ///

    /// ```

    /// use core::fmt::Write;

    /// use zerotrie::ZeroTrieSimpleAscii;

    ///

    /// // A trie with two values: "abc" and "abcdef"

    /// let trie = ZeroTrieSimpleAscii::from_bytes(b"abc\x80def\x81");

    ///

    /// // Get out the value for "abc"

    /// let mut cursor = trie.cursor();

    /// write!(&mut cursor, "abc");

    /// assert_eq!(cursor.take_value(), Some(0));

    /// ```

    ///

    /// Find the longest prefix match:

    ///

    /// ```

    /// use zerotrie::ZeroTrieSimpleAscii;

    ///

    /// // A trie with two values: "abc" and "abcdef"

    /// let trie = ZeroTrieSimpleAscii::from_bytes(b"abc\x80def\x81");

    ///

    /// // Find the longest prefix of the string "abcdxy":

    /// let query = b"abcdxy";

    /// let mut longest_prefix = 0;

    /// let mut cursor = trie.cursor();

    /// for (i, b) in query.iter().enumerate() {

    ///     // Checking is_empty() is not required, but it is

    ///     // good for efficiency

    ///     if cursor.is_empty() {

    ///         break;

    ///     }

    ///     if cursor.take_value().is_some() {

    ///         longest_prefix = i;

    ///     }

    ///     cursor.step(*b);

    /// }

    ///

    /// // The longest prefix is "abc" which is length 3:

    /// assert_eq!(longest_prefix, 3);

    /// ```

    #[inline]

    pub fn cursor(&self) -> ZeroTrieSimpleAsciiCursor {

        ZeroTrieSimpleAsciiCursor {

            trie: self.as_borrowed_slice(),

        }

    }

}

impl<Store> ZeroAsciiIgnoreCaseTrie<Store>

where

    Store: AsRef<[u8]> + ?Sized,

{

    /// Gets a cursor into the current trie.

    ///

    /// Useful to query a trie with data that is not a slice.

    ///

    /// This is currently supported only on [`ZeroTrieSimpleAscii`]

    /// and [`ZeroAsciiIgnoreCaseTrie`].

    ///

    /// # Examples

    ///

    /// Get a value out of a trie by [writing](fmt::Write) it to the cursor:

    ///

    /// ```

    /// use core::fmt::Write;

    /// use zerotrie::ZeroAsciiIgnoreCaseTrie;

    ///

    /// // A trie with two values: "aBc" and "aBcdEf"

    /// let trie = ZeroAsciiIgnoreCaseTrie::from_bytes(b"aBc\x80dEf\x81");

    ///

    /// // Get out the value for "abc" (case-insensitive!)

    /// let mut cursor = trie.cursor();

    /// write!(&mut cursor, "abc");

    /// assert_eq!(cursor.take_value(), Some(0));

    /// ```

    ///

    /// For more examples, see [`ZeroTrieSimpleAscii::cursor`].

    #[inline]

    pub fn cursor(&self) -> ZeroAsciiIgnoreCaseTrieCursor {

        ZeroAsciiIgnoreCaseTrieCursor {

            trie: self.as_borrowed_slice(),

        }

    }

Unexecuted instantiation: <zerotrie::zerotrie::ZeroAsciiIgnoreCaseTrie<zerovec::zerovec::ZeroVec<u8>>>::cursor

Unexecuted instantiation: <zerotrie::zerotrie::ZeroAsciiIgnoreCaseTrie<_>>::cursor

}

impl<'a> ZeroTrieSimpleAscii<&'a [u8]> {

    /// Same as [`ZeroTrieSimpleAscii::cursor()`] but moves self to avoid

    /// having to doubly anchor the trie to the stack.

    #[inline]

    pub fn into_cursor(self) -> ZeroTrieSimpleAsciiCursor<'a> {

        ZeroTrieSimpleAsciiCursor { trie: self }

    }

}

impl<'a> ZeroAsciiIgnoreCaseTrie<&'a [u8]> {

    /// Same as [`ZeroAsciiIgnoreCaseTrie::cursor()`] but moves self to avoid

    /// having to doubly anchor the trie to the stack.

    #[inline]

    pub fn into_cursor(self) -> ZeroAsciiIgnoreCaseTrieCursor<'a> {

        ZeroAsciiIgnoreCaseTrieCursor { trie: self }

    }

}

/// A cursor into a [`ZeroTrieSimpleAscii`], useful for stepwise lookup.

///

/// For examples, see [`ZeroTrieSimpleAscii::cursor()`].

// Clone but not Copy: <https://stackoverflow.com/q/32324251/1407170>

#[derive(Debug, Clone)]

pub struct ZeroTrieSimpleAsciiCursor<'a> {

    trie: ZeroTrieSimpleAscii<&'a [u8]>,

}

/// A cursor into a [`ZeroAsciiIgnoreCaseTrie`], useful for stepwise lookup.

///

/// For examples, see [`ZeroAsciiIgnoreCaseTrie::cursor()`].

// Clone but not Copy: <https://stackoverflow.com/q/32324251/1407170>

#[derive(Debug, Clone)]

pub struct ZeroAsciiIgnoreCaseTrieCursor<'a> {

    trie: ZeroAsciiIgnoreCaseTrie<&'a [u8]>,

}

/// Information about a probed edge.

#[derive(Debug, Copy, Clone, PartialEq, Eq)]

#[non_exhaustive] // no need to destructure or construct this in userland

pub struct AsciiProbeResult {

    /// The character's byte value between this node and its parent.

    pub byte: u8,

    /// The number of siblings of this node, _including itself_.

    pub total_siblings: u8,

}

impl<'a> ZeroTrieSimpleAsciiCursor<'a> {

    /// Steps the cursor one character into the trie based on the character's byte value.

    ///

    /// # Examples

    ///

    /// Unrolled loop checking for string presence at every step:

    ///

    /// ```

    /// use zerotrie::ZeroTrieSimpleAscii;

    ///

    /// // A trie with two values: "abc" and "abcdef"

    /// let trie = ZeroTrieSimpleAscii::from_bytes(b"abc\x80def\x81");

    ///

    /// // Search the trie for the string "abcdxy"

    /// let mut cursor = trie.cursor();

    /// assert_eq!(cursor.take_value(), None); // ""

    /// cursor.step(b'a');

    /// assert_eq!(cursor.take_value(), None); // "a"

    /// cursor.step(b'b');

    /// assert_eq!(cursor.take_value(), None); // "ab"

    /// cursor.step(b'c');

    /// assert_eq!(cursor.take_value(), Some(0)); // "abc"

    /// cursor.step(b'd');

    /// assert_eq!(cursor.take_value(), None); // "abcd"

    /// assert!(!cursor.is_empty());

    /// cursor.step(b'x'); // no strings have the prefix "abcdx"

    /// assert!(cursor.is_empty());

    /// assert_eq!(cursor.take_value(), None); // "abcdx"

    /// cursor.step(b'y');

    /// assert_eq!(cursor.take_value(), None); // "abcdxy"

    /// ```

    ///

    /// If the byte is not ASCII, the cursor will become empty:

    ///

    /// ```

    /// use zerotrie::ZeroTrieSimpleAscii;

    ///

    /// // A trie with two values: "abc" and "abcdef"

    /// let trie = ZeroTrieSimpleAscii::from_bytes(b"abc\x80def\x81");

    ///

    /// let mut cursor = trie.cursor();

    /// assert_eq!(cursor.take_value(), None); // ""

    /// cursor.step(b'a');

    /// assert_eq!(cursor.take_value(), None); // "a"

    /// cursor.step(b'b');

    /// assert_eq!(cursor.take_value(), None); // "ab"

    /// cursor.step(b'\xFF');

    /// assert!(cursor.is_empty());

    /// assert_eq!(cursor.take_value(), None);

    /// ```

    #[inline]

    pub fn step(&mut self, byte: u8) {

        reader::step_parameterized::<ZeroTrieSimpleAscii<[u8]>>(&mut self.trie.store, byte);

    }

    /// Takes the value at the current position.

    ///

    /// Calling this function on a new cursor is equivalent to calling `.get()`

    /// with the empty string (except that it can only be called once).

    ///

    /// # Examples

    ///

    /// ```

    /// use zerotrie::ZeroTrieSimpleAscii;

    ///

    /// // A trie with two values: "" and "abc"

    /// let trie = ZeroTrieSimpleAscii::from_bytes(b"\x80abc\x81");

    ///

    /// assert_eq!(Some(0), trie.get(""));

    /// let mut cursor = trie.cursor();

    /// assert_eq!(Some(0), cursor.take_value());

    /// assert_eq!(None, cursor.take_value());

    /// ```

    #[inline]

    pub fn take_value(&mut self) -> Option<usize> {

        reader::take_value(&mut self.trie.store)

    }

    /// Steps the cursor one character into the trie based on an edge index,

    /// returning the corresponding character as a byte.

    ///

    /// This function is similar to [`Self::step()`], but it takes an index instead of a char.

    /// This enables stepwise iteration over the contents of the trie.

    ///

    /// If there are multiple possibilities for the next byte, the `index` argument allows

    /// visiting them in order. Since this function steps the cursor, the cursor must be

    /// cloned (a cheap operation) in order to visit multiple children.

    ///

    /// # Examples

    ///

    /// Continually query index 0 to extract the first item from a trie:

    ///

    /// ```

    /// use zerotrie::ZeroTrieSimpleAscii;

    ///

    /// let data: &[(String, usize)] = &[

    ///     ("ab".to_string(), 111),

    ///     ("abcxyz".to_string(), 22),

    ///     ("abde".to_string(), 333),

    ///     ("afg".to_string(), 44),

    /// ];

    ///

    /// let trie: ZeroTrieSimpleAscii<Vec<u8>> =

    ///     data.iter().map(|(s, v)| (s.as_str(), *v)).collect();

    ///

    /// let mut cursor = trie.cursor();

    /// let mut key = String::new();

    /// let value = loop {

    ///     if let Some(value) = cursor.take_value() {

    ///         break value;

    ///     }

    ///     let probe_result = cursor.probe(0).unwrap();

    ///     key.push(char::from(probe_result.byte));

    /// };

    ///

    /// assert_eq!(key, "ab");

    /// assert_eq!(value, 111);

    /// ```

    ///

    /// Stepwise iterate over all entries in the trie:

    ///

    /// ```

    /// # use zerotrie::ZeroTrieSimpleAscii;

    /// # let data: &[(String, usize)] = &[

    /// #     ("ab".to_string(), 111),

    /// #     ("abcxyz".to_string(), 22),

    /// #     ("abde".to_string(), 333),

    /// #     ("afg".to_string(), 44)

    /// # ];

    /// # let trie: ZeroTrieSimpleAscii<Vec<u8>> = data

    /// #     .iter()

    /// #     .map(|(s, v)| (s.as_str(), *v))

    /// #     .collect();

    /// // (trie built as in previous example)

    ///

    /// // Initialize the iteration at the first child of the trie.

    /// let mut stack = Vec::from([(trie.cursor(), 0, 0)]);

    /// let mut key = Vec::new();

    /// let mut results = Vec::new();

    /// loop {

    ///     let Some((mut cursor, index, suffix_len)) = stack.pop() else {

    ///         // Nothing left in the trie.

    ///         break;

    ///     };

    ///     // Check to see if there is a value at the current node.

    ///     if let Some(value) = cursor.take_value() {

    ///         results.push((String::from_utf8(key.clone()).unwrap(), value));

    ///     }

    ///     // Now check for children of the current node.

    ///     let mut sub_cursor = cursor.clone();

    ///     if let Some(probe_result) = sub_cursor.probe(index) {

    ///         // Found a child. Add the current byte edge to the key.

    ///         key.push(probe_result.byte);

    ///         // Add the child to the stack, and also add back the current

    ///         // node if there are more siblings to visit.

    ///         if index + 1 < probe_result.total_siblings as usize {

    ///             stack.push((cursor, index + 1, suffix_len));

    ///             stack.push((sub_cursor, 0, 1));

    ///         } else {

    ///             stack.push((sub_cursor, 0, suffix_len + 1));

    ///         }

    ///     } else {

    ///         // No more children. Pop this node's bytes from the key.

    ///         for _ in 0..suffix_len {

    ///             key.pop();

    ///         }

    ///     }

    /// }

    ///

    /// assert_eq!(&results, data);

    /// ```

    pub fn probe(&mut self, index: usize) -> Option<AsciiProbeResult> {

        reader::probe_parameterized::<ZeroTrieSimpleAscii<[u8]>>(&mut self.trie.store, index)

    }

    /// Checks whether the cursor points to an empty trie.

    ///

    /// Use this to determine when to stop iterating.

    #[inline]

    pub fn is_empty(&self) -> bool {

        self.trie.is_empty()

    }

}

impl<'a> ZeroAsciiIgnoreCaseTrieCursor<'a> {

    /// Steps the cursor one byte into the trie.

    ///

    /// Returns the byte if matched, which may be a different case than the input byte.

    /// If this function returns `None`, any lookup loops can be terminated.

    ///

    /// # Examples

    ///

    /// Normalize the case of a value by stepping through an ignore-case trie:

    ///

    /// ```

    /// use std::borrow::Cow;

    /// use zerotrie::ZeroAsciiIgnoreCaseTrie;

    ///

    /// // A trie with two values: "aBc" and "aBcdEf"

    /// let trie = ZeroAsciiIgnoreCaseTrie::from_bytes(b"aBc\x80dEf\x81");

    ///

    /// // Get out the value for "abc" and normalize the key string

    /// let mut cursor = trie.cursor();

    /// let mut key_str = Cow::Borrowed("abc".as_bytes());

    /// let mut i = 0;

    /// let value = loop {

    ///     let Some(&input_byte) = key_str.get(i) else {

    ///         break cursor.take_value();

    ///     };

    ///     let Some(matched_byte) = cursor.step(input_byte) else {

    ///         break None;

    ///     };

    ///     if matched_byte != input_byte {

    ///         key_str.to_mut()[i] = matched_byte;

    ///     }

    ///     i += 1;

    /// };

    ///

    /// assert_eq!(value, Some(0));

    /// assert_eq!(&*key_str, "aBc".as_bytes());

    /// ```

    ///

    /// For more examples, see [`ZeroTrieSimpleAsciiCursor::step`].

    #[inline]

    pub fn step(&mut self, byte: u8) -> Option<u8> {

        reader::step_parameterized::<ZeroAsciiIgnoreCaseTrie<[u8]>>(&mut self.trie.store, byte)

    }

Unexecuted instantiation: <zerotrie::cursor::ZeroAsciiIgnoreCaseTrieCursor>::step

Unexecuted instantiation: <zerotrie::cursor::ZeroAsciiIgnoreCaseTrieCursor>::step

    /// Takes the value at the current position.

    ///

    /// For more details, see [`ZeroTrieSimpleAsciiCursor::take_value`].

    #[inline]

    pub fn take_value(&mut self) -> Option<usize> {

        reader::take_value(&mut self.trie.store)

    }

Unexecuted instantiation: <zerotrie::cursor::ZeroAsciiIgnoreCaseTrieCursor>::take_value

Unexecuted instantiation: <zerotrie::cursor::ZeroAsciiIgnoreCaseTrieCursor>::take_value

    /// Probes the next byte in the cursor.

    ///

    /// For more details, see [`ZeroTrieSimpleAsciiCursor::probe`].

    pub fn probe(&mut self, index: usize) -> Option<AsciiProbeResult> {

        reader::probe_parameterized::<ZeroAsciiIgnoreCaseTrie<[u8]>>(&mut self.trie.store, index)

    }

    /// Checks whether the cursor points to an empty trie.

    ///

    /// For more details, see [`ZeroTrieSimpleAsciiCursor::is_empty`].

    #[inline]

    pub fn is_empty(&self) -> bool {

        self.trie.is_empty()

    }

}

impl<'a> fmt::Write for ZeroTrieSimpleAsciiCursor<'a> {

    /// Steps the cursor through each ASCII byte of the string.

    ///

    /// If the string contains non-ASCII chars, an error is returned.

    ///

    /// # Examples

    ///

    /// ```

    /// use core::fmt::Write;

    /// use zerotrie::ZeroTrieSimpleAscii;

    ///

    /// // A trie with two values: "abc" and "abcdef"

    /// let trie = ZeroTrieSimpleAscii::from_bytes(b"abc\x80def\x81");

    ///

    /// let mut cursor = trie.cursor();

    /// cursor.write_str("abcdxy").expect("all ASCII");

    /// cursor.write_str("🚂").expect_err("non-ASCII");

    /// ```

    fn write_str(&mut self, s: &str) -> fmt::Result {

        for b in s.bytes() {

            if !b.is_ascii() {

                return Err(fmt::Error);

            }

            self.step(b);

        }

        Ok(())

    }

    /// Equivalent to [`ZeroTrieSimpleAsciiCursor::step()`], except returns

    /// an error if the char is non-ASCII.

    ///

    /// # Examples

    ///

    /// ```

    /// use core::fmt::Write;

    /// use zerotrie::ZeroTrieSimpleAscii;

    ///

    /// // A trie with two values: "abc" and "abcdef"

    /// let trie = ZeroTrieSimpleAscii::from_bytes(b"abc\x80def\x81");

    ///

    /// let mut cursor = trie.cursor();

    /// cursor.write_char('a').expect("ASCII");

    /// cursor.write_char('x').expect("ASCII");

    /// cursor.write_char('🚂').expect_err("non-ASCII");

    /// ```

    fn write_char(&mut self, c: char) -> fmt::Result {

        if !c.is_ascii() {

            return Err(fmt::Error);

        }

        self.step(c as u8);

        Ok(())

    }

}

impl<'a> fmt::Write for ZeroAsciiIgnoreCaseTrieCursor<'a> {

    /// Steps the cursor through each ASCII byte of the string.

    ///

    /// If the string contains non-ASCII chars, an error is returned.

    fn write_str(&mut self, s: &str) -> fmt::Result {

        for b in s.bytes() {

            if !b.is_ascii() {

                return Err(fmt::Error);

            }

            self.step(b);

        }

        Ok(())

    }

    /// Equivalent to [`ZeroAsciiIgnoreCaseTrieCursor::step()`], except returns

    /// an error if the char is non-ASCII.

    fn write_char(&mut self, c: char) -> fmt::Result {

        if !c.is_ascii() {

            return Err(fmt::Error);

        }

        self.step(c as u8);

        Ok(())

    }

}