#![allow(clippy::module_name_repetitions)]

use std::{collections::BTreeMap, convert::TryFrom, mem, ops::Index};

use hashlink::LinkedHashMap;

use crate::parser::{Event, MarkedEventReceiver, Parser, Tag};
use crate::scanner::{Marker, ScanError, TScalarStyle};

/// A YAML node is stored as this `Yaml` enumeration, which provides an easy way to
/// access your YAML document.
///
/// # Examples
///
/// ```
/// use yaml_rust2::Yaml;
/// let foo = Yaml::from_str("-123"); // convert the string to the appropriate YAML type
/// assert_eq!(foo.as_i64().unwrap(), -123);
///
/// // iterate over an Array
/// let vec = Yaml::Array(vec![Yaml::Integer(1), Yaml::Integer(2)]);
/// for v in vec.as_vec().unwrap() {
///     assert!(v.as_i64().is_some());
/// }
/// ```
#[derive(Clone, PartialEq, PartialOrd, Debug, Eq, Ord, Hash)]
pub enum Yaml {
    /// Float types are stored as String and parsed on demand.
    /// Note that `f64` does NOT implement Eq trait and can NOT be stored in `BTreeMap`.
    Real(String),
    /// YAML int is stored as i64.
    Integer(i64),
    /// YAML scalar.
    String(String),
    /// YAML bool, e.g. `true` or `false`.
    Boolean(bool),
    /// YAML array, can be accessed as a `Vec`.
    Array(Array),
    /// YAML hash, can be accessed as a `LinkedHashMap`.
    ///
    /// Insertion order will match the order of insertion into the map.
    Hash(Hash),
    /// Alias, not fully supported yet.
    Alias(usize),
    /// YAML null, e.g. `null` or `~`.
    Null,
    /// Accessing a nonexistent node via the Index trait returns `BadValue`. This
    /// simplifies error handling in the calling code. Invalid type conversion also
    /// returns `BadValue`.
    BadValue,
}

pub type Array = Vec<Yaml>;
pub type Hash = LinkedHashMap<Yaml, Yaml>;

// parse f64 as Core schema
// See: https://github.com/chyh1990/yaml-rust/issues/51
fn parse_f64(v: &str) -> Option<f64> {
    match v {
        ".inf" | ".Inf" | ".INF" | "+.inf" | "+.Inf" | "+.INF" => Some(f64::INFINITY),
        "-.inf" | "-.Inf" | "-.INF" => Some(f64::NEG_INFINITY),
        ".nan" | "NaN" | ".NAN" => Some(f64::NAN),
        _ => v.parse::<f64>().ok(),
    }
}

/// Main structure for quickly parsing YAML.
///
/// See [`YamlLoader::load_from_str`].
#[derive(Default)]
pub struct YamlLoader {
    docs: Vec<Yaml>,
    // states
    // (current node, anchor_id) tuple
    doc_stack: Vec<(Yaml, usize)>,
    key_stack: Vec<Yaml>,
    anchor_map: BTreeMap<usize, Yaml>,
}

impl MarkedEventReceiver for YamlLoader {
    fn on_event(&mut self, ev: Event, _: Marker) {
        // println!("EV {:?}", ev);
        match ev {
            Event::DocumentStart => {
                // do nothing
            }
            Event::DocumentEnd => {
                match self.doc_stack.len() {
                    // empty document
                    0 => self.docs.push(Yaml::BadValue),
                    1 => self.docs.push(self.doc_stack.pop().unwrap().0),
                    _ => unreachable!(),
                }
            }
            Event::SequenceStart(aid, _) => {
                self.doc_stack.push((Yaml::Array(Vec::new()), aid));
            }
            Event::SequenceEnd => {
                let node = self.doc_stack.pop().unwrap();
                self.insert_new_node(node);
            }
            Event::MappingStart(aid, _) => {
                self.doc_stack.push((Yaml::Hash(Hash::new()), aid));
                self.key_stack.push(Yaml::BadValue);
            }
            Event::MappingEnd => {
                self.key_stack.pop().unwrap();
                let node = self.doc_stack.pop().unwrap();
                self.insert_new_node(node);
            }
            Event::Scalar(v, style, aid, tag) => {
                let node = if style != TScalarStyle::Plain {
                    Yaml::String(v)
                } else if let Some(Tag {
                    ref handle,
                    ref suffix,
                }) = tag
                {
                    if handle == "tag:yaml.org,2002:" {
                        match suffix.as_ref() {
                            "bool" => {
                                // "true" or "false"
                                match v.parse::<bool>() {
                                    Err(_) => Yaml::BadValue,
                                    Ok(v) => Yaml::Boolean(v),
                                }
                            }
                            "int" => match v.parse::<i64>() {
                                Err(_) => Yaml::BadValue,
                                Ok(v) => Yaml::Integer(v),
                            },
                            "float" => match parse_f64(&v) {
                                Some(_) => Yaml::Real(v),
                                None => Yaml::BadValue,
                            },
                            "null" => match v.as_ref() {
                                "~" | "null" => Yaml::Null,
                                _ => Yaml::BadValue,
                            },
                            _ => Yaml::String(v),
                        }
                    } else {
                        Yaml::String(v)
                    }
                } else {
                    // Datatype is not specified, or unrecognized
                    Yaml::from_str(&v)
                };

                self.insert_new_node((node, aid));
            }
            Event::Alias(id) => {
                let n = match self.anchor_map.get(&id) {
                    Some(v) => v.clone(),
                    None => Yaml::BadValue,
                };
                self.insert_new_node((n, 0));
            }
            _ => { /* ignore */ }
        }
        // println!("DOC {:?}", self.doc_stack);
    }
}

#[derive(Debug)]
pub enum LoadError {
    IO(std::io::Error),
    Scan(ScanError),
    Decode(std::borrow::Cow<'static, str>),
}

impl From<std::io::Error> for LoadError {
    fn from(error: std::io::Error) -> Self {
        LoadError::IO(error)
    }
}

impl YamlLoader {
    fn insert_new_node(&mut self, node: (Yaml, usize)) {
        // valid anchor id starts from 1
        if node.1 > 0 {
            self.anchor_map.insert(node.1, node.0.clone());
        }
        if self.doc_stack.is_empty() {
            self.doc_stack.push(node);
        } else {
            let parent = self.doc_stack.last_mut().unwrap();
            match *parent {
                (Yaml::Array(ref mut v), _) => v.push(node.0),
                (Yaml::Hash(ref mut h), _) => {
                    let cur_key = self.key_stack.last_mut().unwrap();
                    // current node is a key
                    if cur_key.is_badvalue() {
                        *cur_key = node.0;
                    // current node is a value
                    } else {
                        let mut newkey = Yaml::BadValue;
                        mem::swap(&mut newkey, cur_key);
                        h.insert(newkey, node.0);
                    }
                }
                _ => unreachable!(),
            }
        }
    }

    /// Load the given string as a set of YAML documents.
    ///
    /// The `source` is interpreted as YAML documents and is parsed. Parsing succeeds if and only
    /// if all documents are parsed successfully. An error in a latter document prevents the former
    /// from being returned.
    pub fn load_from_str(source: &str) -> Result<Vec<Yaml>, ScanError> {
        Self::load_from_iter(source.chars())
    }

    /// Load the contents of the given iterator as a set of YAML documents.
    ///
    /// The `source` is interpreted as YAML documents and is parsed. Parsing succeeds if and only
    /// if all documents are parsed successfully. An error in a latter document prevents the former
    /// from being returned.
    pub fn load_from_iter<I: Iterator<Item = char>>(source: I) -> Result<Vec<Yaml>, ScanError> {
        let mut loader = YamlLoader::default();
        let mut parser = Parser::new(source);
        parser.load(&mut loader, true)?;
        Ok(loader.docs)
    }

    pub fn load_from_bytes(mut source: impl std::io::Read) -> Result<Vec<Yaml>, LoadError> {
        let mut buffer = Vec::new();
        source.read_to_end(&mut buffer)?;

        // Decodes the input buffer using either UTF-8, UTF-16LE or UTF-16BE depending on the BOM codepoint.
        // If the buffer doesn't start with a BOM codepoint, it will use a fallback encoding obtained by
        // detect_utf16_endianness.
        let (res, _) = encoding::types::decode(
            &buffer,
            encoding::DecoderTrap::Strict,
            detect_utf16_endianness(&buffer),
        );
        let s = res.map_err(LoadError::Decode)?;
        YamlLoader::load_from_str(&s).map_err(LoadError::Scan)
    }
}

/// The encoding crate knows how to tell apart UTF-8 from UTF-16LE and utf-16BE, when the
/// bytestream starts with BOM codepoint.
/// However, it doesn't even attempt to guess the UTF-16 endianness of the input bytestream since
/// in the general case the bytestream could start with a codepoint that uses both bytes.
///
/// The YAML-1.2 spec mandates that the first character of a YAML document is an ASCII character.
/// This allows the encoding to be deduced by the pattern of null (#x00) characters.
//
/// See spec at <https://yaml.org/spec/1.2/spec.html#id2771184>
fn detect_utf16_endianness(b: &[u8]) -> encoding::types::EncodingRef {
    if b.len() > 1 && (b[0] != b[1]) {
        if b[0] == 0 {
            return encoding::all::UTF_16BE;
        } else if b[1] == 0 {
            return encoding::all::UTF_16LE;
        }
    }
    encoding::all::UTF_8
}

macro_rules! define_as (
    ($name:ident, $t:ident, $yt:ident) => (
#[must_use]
pub fn $name(&self) -> Option<$t> {
    match *self {
        Yaml::$yt(v) => Some(v),
        _ => None
    }
}
    );
);

macro_rules! define_as_ref (
    ($name:ident, $t:ty, $yt:ident) => (
#[must_use]
pub fn $name(&self) -> Option<$t> {
    match *self {
        Yaml::$yt(ref v) => Some(v),
        _ => None
    }
}
    );
);

macro_rules! define_into (
    ($name:ident, $t:ty, $yt:ident) => (
#[must_use]
pub fn $name(self) -> Option<$t> {
    match self {
        Yaml::$yt(v) => Some(v),
        _ => None
    }
}
    );
);

impl Yaml {
    define_as!(as_bool, bool, Boolean);
    define_as!(as_i64, i64, Integer);

    define_as_ref!(as_str, &str, String);
    define_as_ref!(as_hash, &Hash, Hash);
    define_as_ref!(as_vec, &Array, Array);

    define_into!(into_bool, bool, Boolean);
    define_into!(into_i64, i64, Integer);
    define_into!(into_string, String, String);
    define_into!(into_hash, Hash, Hash);
    define_into!(into_vec, Array, Array);

    /// Return whether `self` is a [`Yaml::Null`] node.
    #[must_use]
    pub fn is_null(&self) -> bool {
        matches!(*self, Yaml::Null)
    }

    /// Return whether `self` is a [`Yaml::BadValue`] node.
    #[must_use]
    pub fn is_badvalue(&self) -> bool {
        matches!(*self, Yaml::BadValue)
    }

    /// Return whether `self` is a [`Yaml::Array`] node.
    #[must_use]
    pub fn is_array(&self) -> bool {
        matches!(*self, Yaml::Array(_))
    }

    /// Return the `f64` value contained in this YAML node.
    ///
    /// If the node is not a [`Yaml::Real`] YAML node or its contents is not a valid `f64` string,
    /// `None` is returned.
    #[must_use]
    pub fn as_f64(&self) -> Option<f64> {
        if let Yaml::Real(ref v) = self {
            parse_f64(v)
        } else {
            None
        }
    }

    /// Return the `f64` value contained in this YAML node.
    ///
    /// If the node is not a [`Yaml::Real`] YAML node or its contents is not a valid `f64` string,
    /// `None` is returned.
    #[must_use]
    pub fn into_f64(self) -> Option<f64> {
        self.as_f64()
    }
}

#[cfg_attr(feature = "cargo-clippy", allow(clippy::should_implement_trait))]
impl Yaml {
    /// Convert a string to a [`Yaml`] node.
    ///
    /// [`Yaml`] does not implement [`std::str::FromStr`] since conversion may not fail. This
    /// function falls back to [`Yaml::String`] if nothing else matches.
    ///
    /// # Examples
    /// ```
    /// # use yaml_rust2::yaml::Yaml;
    /// assert!(matches!(Yaml::from_str("42"), Yaml::Integer(42)));
    /// assert!(matches!(Yaml::from_str("0x2A"), Yaml::Integer(42)));
    /// assert!(matches!(Yaml::from_str("0o52"), Yaml::Integer(42)));
    /// assert!(matches!(Yaml::from_str("~"), Yaml::Null));
    /// assert!(matches!(Yaml::from_str("null"), Yaml::Null));
    /// assert!(matches!(Yaml::from_str("true"), Yaml::Boolean(true)));
    /// assert!(matches!(Yaml::from_str("3.14"), Yaml::Real(_)));
    /// assert!(matches!(Yaml::from_str("foo"), Yaml::String(_)));
    /// ```
    #[must_use]
    pub fn from_str(v: &str) -> Yaml {
        if let Some(number) = v.strip_prefix("0x") {
            if let Ok(i) = i64::from_str_radix(number, 16) {
                return Yaml::Integer(i);
            }
        } else if let Some(number) = v.strip_prefix("0o") {
            if let Ok(i) = i64::from_str_radix(number, 8) {
                return Yaml::Integer(i);
            }
        } else if let Some(number) = v.strip_prefix('+') {
            if let Ok(i) = number.parse::<i64>() {
                return Yaml::Integer(i);
            }
        }
        match v {
            "~" | "null" => Yaml::Null,
            "true" => Yaml::Boolean(true),
            "false" => Yaml::Boolean(false),
            _ => {
                if let Ok(integer) = v.parse::<i64>() {
                    Yaml::Integer(integer)
                } else if parse_f64(v).is_some() {
                    Yaml::Real(v.to_owned())
                } else {
                    Yaml::String(v.to_owned())
                }
            }
        }
    }
}

static BAD_VALUE: Yaml = Yaml::BadValue;
impl<'a> Index<&'a str> for Yaml {
    type Output = Yaml;

    fn index(&self, idx: &'a str) -> &Yaml {
        let key = Yaml::String(idx.to_owned());
        match self.as_hash() {
            Some(h) => h.get(&key).unwrap_or(&BAD_VALUE),
            None => &BAD_VALUE,
        }
    }
}

impl Index<usize> for Yaml {
    type Output = Yaml;

    fn index(&self, idx: usize) -> &Yaml {
        if let Some(v) = self.as_vec() {
            v.get(idx).unwrap_or(&BAD_VALUE)
        } else if let Some(v) = self.as_hash() {
            let key = Yaml::Integer(i64::try_from(idx).unwrap());
            v.get(&key).unwrap_or(&BAD_VALUE)
        } else {
            &BAD_VALUE
        }
    }
}

impl IntoIterator for Yaml {
    type Item = Yaml;
    type IntoIter = YamlIter;

    fn into_iter(self) -> Self::IntoIter {
        YamlIter {
            yaml: self.into_vec().unwrap_or_default().into_iter(),
        }
    }
}

/// An iterator over a [`Yaml`] node.
pub struct YamlIter {
    yaml: std::vec::IntoIter<Yaml>,
}

impl Iterator for YamlIter {
    type Item = Yaml;

    fn next(&mut self) -> Option<Yaml> {
        self.yaml.next()
    }
}

#[cfg(test)]
mod test {
    use crate::YamlLoader;

    #[test]
    fn test_read_bom() {
        let s = b"\xef\xbb\xbf---
a: 1
b: 2.2
c: [1, 2]
";
        let out = YamlLoader::load_from_bytes(s as &[u8]).unwrap();
        let doc = &out[0];
        assert_eq!(doc["a"].as_i64().unwrap(), 1i64);
        assert!((doc["b"].as_f64().unwrap() - 2.2f64).abs() <= f64::EPSILON);
        assert_eq!(doc["c"][1].as_i64().unwrap(), 2i64);
        assert!(doc["d"][0].is_badvalue());
    }

    #[test]
    fn test_read_utf16le() {
        let s = b"\xff\xfe-\x00-\x00-\x00
\x00a\x00:\x00 \x001\x00
\x00b\x00:\x00 \x002\x00.\x002\x00
\x00c\x00:\x00 \x00[\x001\x00,\x00 \x002\x00]\x00
\x00";
        let out = YamlLoader::load_from_bytes(s as &[u8]).unwrap();
        let doc = &out[0];
        println!("GOT: {doc:?}");
        assert_eq!(doc["a"].as_i64().unwrap(), 1i64);
        assert!((doc["b"].as_f64().unwrap() - 2.2f64) <= f64::EPSILON);
        assert_eq!(doc["c"][1].as_i64().unwrap(), 2i64);
        assert!(doc["d"][0].is_badvalue());
    }

    #[test]
    fn test_read_utf16be() {
        let s = b"\xfe\xff\x00-\x00-\x00-\x00
\x00a\x00:\x00 \x001\x00
\x00b\x00:\x00 \x002\x00.\x002\x00
\x00c\x00:\x00 \x00[\x001\x00,\x00 \x002\x00]\x00
";
        let out = YamlLoader::load_from_bytes(s as &[u8]).unwrap();
        let doc = &out[0];
        println!("GOT: {doc:?}");
        assert_eq!(doc["a"].as_i64().unwrap(), 1i64);
        assert!((doc["b"].as_f64().unwrap() - 2.2f64).abs() <= f64::EPSILON);
        assert_eq!(doc["c"][1].as_i64().unwrap(), 2i64);
        assert!(doc["d"][0].is_badvalue());
    }

    #[test]
    fn test_read_utf16le_nobom() {
        let s = b"-\x00-\x00-\x00
\x00a\x00:\x00 \x001\x00
\x00b\x00:\x00 \x002\x00.\x002\x00
\x00c\x00:\x00 \x00[\x001\x00,\x00 \x002\x00]\x00
\x00";
        let out = YamlLoader::load_from_bytes(s as &[u8]).unwrap();
        let doc = &out[0];
        println!("GOT: {doc:?}");
        assert_eq!(doc["a"].as_i64().unwrap(), 1i64);
        assert!((doc["b"].as_f64().unwrap() - 2.2f64).abs() <= f64::EPSILON);
        assert_eq!(doc["c"][1].as_i64().unwrap(), 2i64);
        assert!(doc["d"][0].is_badvalue());
    }
}