//! A BSON document represented as an associative HashMap with insertion ordering.

use std::error;
use std::fmt::{self, Debug, Display, Formatter};
use std::iter::{FromIterator, Map};
use std::marker::PhantomData;

use chrono::{DateTime, Utc};

use linked_hash_map::{self, LinkedHashMap};

use serde::de::{self, Visitor, MapAccess};

use bson::{Array, Bson, Document};
use oid::ObjectId;
use spec::BinarySubtype;

/// Error to indicate that either a value was empty or it contained an unexpected
/// type, for use with the direct getters.
#[derive(PartialEq)]
pub enum ValueAccessError {
    /// Cannot find the expected field with the specified key
    NotPresent,
    /// Found a Bson value with the specified key, but not with the expected type
    UnexpectedType,
}

/// Result of accessing Bson value
pub type ValueAccessResult<T> = Result<T, ValueAccessError>;

impl Debug for ValueAccessError {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        match *self {
            ValueAccessError::NotPresent => write!(f, "ValueAccessError: field is not present"),
            ValueAccessError::UnexpectedType => {
                write!(f, "ValueAccessError: field does not have the expected type")
            }
        }
    }
}

impl Display for ValueAccessError {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        match *self {
            ValueAccessError::NotPresent => write!(f, "field is not present"),
            ValueAccessError::UnexpectedType => write!(f, "field does not have the expected type"),
        }
    }
}

impl error::Error for ValueAccessError {
    fn description(&self) -> &str {
        "Error to indicate that either a value was empty or it contained an unexpected type"
    }
}

/// A BSON document represented as an associative HashMap with insertion ordering.
#[derive(Clone, PartialEq)]
pub struct OrderedDocument {
    inner: LinkedHashMap<String, Bson>,
}

impl Default for OrderedDocument {
    fn default() -> Self {
        Document::new()
    }
}

impl Display for OrderedDocument {
    fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
        try!(write!(fmt, "{{"));

        let mut first = true;
        for (k, v) in self.iter() {
            if first {
                first = false;
                try!(write!(fmt, " "));
            } else {
                try!(write!(fmt, ", "));
            }

            try!(write!(fmt, "{}: {}", k, v));
        }

        try!(write!(fmt, "{}}}", if !first { " " } else { "" }));
        Ok(())
    }
}

impl Debug for OrderedDocument {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        write!(f, "OrderedDocument({:?})", self.inner)
    }
}

/// An iterator over OrderedDocument entries.
pub struct OrderedDocumentIntoIterator {
    inner: LinkedHashMap<String, Bson>,
}

/// An owning iterator over OrderedDocument entries.
pub struct OrderedDocumentIterator<'a> {
    inner: linked_hash_map::Iter<'a, String, Bson>,
}

/// An iterator over an OrderedDocument's keys.
pub struct Keys<'a> {
    inner: Map<OrderedDocumentIterator<'a>, fn((&'a String, &'a Bson)) -> &'a String>,
}

/// An iterator over an OrderedDocument's values.
pub struct Values<'a> {
    inner: Map<OrderedDocumentIterator<'a>, fn((&'a String, &'a Bson)) -> &'a Bson>,
}

impl<'a> Iterator for Keys<'a> {
    type Item = &'a String;
    fn next(&mut self) -> Option<(&'a String)> {
        self.inner.next()
    }
}

impl<'a> Iterator for Values<'a> {
    type Item = &'a Bson;
    fn next(&mut self) -> Option<(&'a Bson)> {
        self.inner.next()
    }
}

impl IntoIterator for OrderedDocument {
    type Item = (String, Bson);
    type IntoIter = OrderedDocumentIntoIterator;

    fn into_iter(self) -> Self::IntoIter {
        OrderedDocumentIntoIterator { inner: self.inner }
    }
}

impl<'a> IntoIterator for &'a OrderedDocument {
    type Item = (&'a String, &'a Bson);
    type IntoIter = OrderedDocumentIterator<'a>;

    fn into_iter(self) -> Self::IntoIter {
        OrderedDocumentIterator { inner: self.inner.iter() }
    }
}

impl FromIterator<(String, Bson)> for OrderedDocument {
    fn from_iter<T: IntoIterator<Item = (String, Bson)>>(iter: T) -> Self {
        let mut doc = OrderedDocument::new();
        for (k, v) in iter {
            doc.insert(k, v.to_owned());
        }
        doc
    }
}

impl<'a> Iterator for OrderedDocumentIntoIterator {
    type Item = (String, Bson);
    fn next(&mut self) -> Option<(String, Bson)> {
        self.inner.pop_front()
    }
}

impl<'a> Iterator for OrderedDocumentIterator<'a> {
    type Item = (&'a String, &'a Bson);
    fn next(&mut self) -> Option<(&'a String, &'a Bson)> {
        self.inner.next()
    }
}

impl OrderedDocument {
    /// Creates a new empty OrderedDocument.
    pub fn new() -> OrderedDocument {
        OrderedDocument { inner: LinkedHashMap::new() }
    }

    /// Gets an iterator over the entries of the map.
    pub fn iter<'a>(&'a self) -> OrderedDocumentIterator<'a> {
        self.into_iter()
    }

    /// Clears the document, removing all values.
    pub fn clear(&mut self) {
        self.inner.clear();
    }

    /// Returns a reference to the Bson corresponding to the key.
    pub fn get(&self, key: &str) -> Option<&Bson> {
        self.inner.get(key)
    }

    /// Gets a mutable reference to the Bson corresponding to the key
    pub fn get_mut(&mut self, key: &str) -> Option<&mut Bson> {
        self.inner.get_mut(key)
    }

    /// Get a floating point value for this key if it exists and has
    /// the correct type.
    pub fn get_f64(&self, key: &str) -> ValueAccessResult<f64> {
        match self.get(key) {
            Some(&Bson::FloatingPoint(v)) => Ok(v),
            Some(_) => Err(ValueAccessError::UnexpectedType),
            None => Err(ValueAccessError::NotPresent),
        }
    }

    /// Get a string slice this key if it exists and has the correct type.
    pub fn get_str(&self, key: &str) -> ValueAccessResult<&str> {
        match self.get(key) {
            Some(&Bson::String(ref v)) => Ok(v),
            Some(_) => Err(ValueAccessError::UnexpectedType),
            None => Err(ValueAccessError::NotPresent),
        }
    }

    /// Get a reference to an array for this key if it exists and has
    /// the correct type.
    pub fn get_array(&self, key: &str) -> ValueAccessResult<&Array> {
        match self.get(key) {
            Some(&Bson::Array(ref v)) => Ok(v),
            Some(_) => Err(ValueAccessError::UnexpectedType),
            None => Err(ValueAccessError::NotPresent),
        }
    }

    /// Get a reference to a document for this key if it exists and has
    /// the correct type.
    pub fn get_document(&self, key: &str) -> ValueAccessResult<&Document> {
        match self.get(key) {
            Some(&Bson::Document(ref v)) => Ok(v),
            Some(_) => Err(ValueAccessError::UnexpectedType),
            None => Err(ValueAccessError::NotPresent),
        }
    }

    /// Get a bool value for this key if it exists and has the correct type.
    pub fn get_bool(&self, key: &str) -> ValueAccessResult<bool> {
        match self.get(key) {
            Some(&Bson::Boolean(v)) => Ok(v),
            Some(_) => Err(ValueAccessError::UnexpectedType),
            None => Err(ValueAccessError::NotPresent),
        }
    }

    /// Returns wether this key has a null value
    pub fn is_null(&self, key: &str) -> bool {
        self.get(key) == Some(&Bson::Null)
    }

    /// Get an i32 value for this key if it exists and has the correct type.
    pub fn get_i32(&self, key: &str) -> ValueAccessResult<i32> {
        match self.get(key) {
            Some(&Bson::I32(v)) => Ok(v),
            Some(_) => Err(ValueAccessError::UnexpectedType),
            None => Err(ValueAccessError::NotPresent),
        }
    }

    /// Get an i64 value for this key if it exists and has the correct type.
    pub fn get_i64(&self, key: &str) -> ValueAccessResult<i64> {
        match self.get(key) {
            Some(&Bson::I64(v)) => Ok(v),
            Some(_) => Err(ValueAccessError::UnexpectedType),
            None => Err(ValueAccessError::NotPresent),
        }
    }

    /// Get a time stamp value for this key if it exists and has the correct type.
    pub fn get_time_stamp(&self, key: &str) -> ValueAccessResult<i64> {
        match self.get(key) {
            Some(&Bson::TimeStamp(v)) => Ok(v),
            Some(_) => Err(ValueAccessError::UnexpectedType),
            None => Err(ValueAccessError::NotPresent),
        }
    }

    /// Get a generic binary value for this key if it exists and has the correct type.
    pub fn get_binary_generic(&self, key: &str) -> ValueAccessResult<&Vec<u8>> {
        match self.get(key) {
            Some(&Bson::Binary(BinarySubtype::Generic, ref v)) => Ok(v),
            Some(_) => Err(ValueAccessError::UnexpectedType),
            None => Err(ValueAccessError::NotPresent),
        }
    }

    /// Get an object id value for this key if it exists and has the correct type.
    pub fn get_object_id(&self, key: &str) -> ValueAccessResult<&ObjectId> {
        match self.get(key) {
            Some(&Bson::ObjectId(ref v)) => Ok(v),
            Some(_) => Err(ValueAccessError::UnexpectedType),
            None => Err(ValueAccessError::NotPresent),
        }
    }

    /// Get a UTC datetime value for this key if it exists and has the correct type.
    pub fn get_utc_datetime(&self, key: &str) -> ValueAccessResult<&DateTime<Utc>> {
        match self.get(key) {
            Some(&Bson::UtcDatetime(ref v)) => Ok(v),
            Some(_) => Err(ValueAccessError::UnexpectedType),
            None => Err(ValueAccessError::NotPresent),
        }
    }

    /// Returns true if the map contains a value for the specified key.
    pub fn contains_key(&self, key: &str) -> bool {
        self.inner.contains_key(key)
    }

    /// Gets a collection of all keys in the document.
    pub fn keys<'a>(&'a self) -> Keys<'a> {
        fn first<A, B>((a, _): (A, B)) -> A {
            a
        }
        let first: fn((&'a String, &'a Bson)) -> &'a String = first;

        Keys { inner: self.iter().map(first) }
    }

    /// Gets a collection of all values in the document.
    pub fn values<'a>(&'a self) -> Values<'a> {
        fn second<A, B>((_, b): (A, B)) -> B {
            b
        }
        let second: fn((&'a String, &'a Bson)) -> &'a Bson = second;

        Values { inner: self.iter().map(second) }
    }

    /// Returns the number of elements in the document.
    pub fn len(&self) -> usize {
        self.inner.len()
    }

    /// Returns true if the document contains no elements
    pub fn is_empty(&self) -> bool {
        self.inner.is_empty()
    }

    /// Sets the value of the entry with the OccupiedEntry's key,
    /// and returns the entry's old value. Accepts any type that
    /// can be converted into Bson.
    pub fn insert<KT: Into<String>, BT: Into<Bson>>(&mut self, key: KT, val: BT) -> Option<Bson> {
        self.insert_bson(key.into(), val.into())
    }

    /// Sets the value of the entry with the OccupiedEntry's key,
    /// and returns the entry's old value.
    pub fn insert_bson(&mut self, key: String, val: Bson) -> Option<Bson> {
        self.inner.insert(key, val)
    }

    /// Takes the value of the entry out of the document, and returns it.
    pub fn remove(&mut self, key: &str) -> Option<Bson> {
        self.inner.remove(key)
    }

    pub fn entry(&mut self, k: String) -> Entry {
        Entry {
            inner: self.inner.entry(k),
        }
    }
}

pub struct Entry<'a> {
    inner: linked_hash_map::Entry<'a, String, Bson>,
}

impl<'a> Entry<'a> {
    pub fn key(&self) -> &str {
        self.inner.key()
    }

    pub fn or_insert(self, default: Bson) -> &'a mut Bson {
        self.inner.or_insert(default)
    }

    pub fn or_insert_with<F: FnOnce() -> Bson>(self, default: F) -> &'a mut Bson {
        self.inner.or_insert_with(default)
    }
}

impl From<LinkedHashMap<String, Bson>> for OrderedDocument {
    fn from(tree: LinkedHashMap<String, Bson>) -> OrderedDocument {
        OrderedDocument { inner: tree }
    }
}

pub struct OrderedDocumentVisitor {
    marker: PhantomData<OrderedDocument>,
}

impl OrderedDocumentVisitor {
    pub fn new() -> OrderedDocumentVisitor {
        OrderedDocumentVisitor { marker: PhantomData }
    }
}

impl<'de> Visitor<'de> for OrderedDocumentVisitor {
    type Value = OrderedDocument;

    fn expecting(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "expecting ordered document")
    }

    #[inline]
    fn visit_unit<E>(self) -> Result<OrderedDocument, E>
        where E: de::Error
    {
        Ok(OrderedDocument::new())
    }

    #[inline]
    fn visit_map<V>(self, mut visitor: V) -> Result<OrderedDocument, V::Error>
        where V: MapAccess<'de>
    {
        let mut inner = match visitor.size_hint() {
            Some(size) => LinkedHashMap::with_capacity(size),
            None => LinkedHashMap::new(),
        };

        while let Some((key, value)) = try!(visitor.next_entry()) {
            inner.insert(key, value);
        }

        Ok(inner.into())
    }
}