use std::str;
use std::convert::From;
use std::fmt::{Debug, Display, Formatter, Result as FmtResult};

/// In-memory representation of a RESP value.
#[derive(Clone, Eq, PartialEq)]
pub enum Value {
    /// An integer.
    Int(i64),
    /// A simple string.
    Str(String),
    /// An error.
    Err(String),
    /// A bulk string.
    BStr(Option<String>),
    /// An array.
    Array(Option<Vec<Value>>),
}

impl Value {
    // BStr constants
    const ENCODED_NULL_BSTR: &'static str = "$-1\r\n";
    const ENCODED_EMPTY_BSTR: &'static str = "$0\r\n\r\n";

    // Array constants
    const ENCODED_NULL_ARRAY: &'static str = "*-1\r\n";
    const ENCODED_EMPTY_ARRAY: &'static str = "*0\r\n";

    /// Encodes a `Value` as a string.
    ///
    /// # Examples
    ///
    /// ```
    /// use lib_resp::Value;
    ///
    /// let error = Value::err("ERR");
    ///
    /// assert_eq!(error.encode(), "-ERR\r\n");
    /// ```
    pub fn encode(&self) -> String {
        match self {
            &Value::Int(ref datum) => {
                let datum_str = &datum.to_string();

                let mut encoded = String::with_capacity(datum_str.len() + 3);

                encoded.push(':');

                encoded.push_str(datum_str);

                encoded.push_str("\r\n");

                encoded
            }

            &Value::Str(ref datum) => {
                let mut encoded = String::with_capacity(datum.len() + 3);

                encoded.push('+');

                encoded.push_str(datum);

                encoded.push_str("\r\n");

                encoded
            }

            &Value::Err(ref datum) => {
                let mut encoded = String::with_capacity(datum.len() + 3);

                encoded.push('-');

                encoded.push_str(datum);

                encoded.push_str("\r\n");

                encoded
            }

            &Value::BStr(ref inner) => match inner {
                &None => Value::ENCODED_NULL_BSTR.to_owned(),

                &Some(ref datum) => match datum.len() {
                    0 => Value::ENCODED_EMPTY_BSTR.to_owned(),

                    len => {
                        let len_str = &len.to_string();

                        let mut encoded = String::with_capacity(len + len_str.len() + 5);

                        encoded.push('$');

                        encoded.push_str(len_str);

                        encoded.push_str("\r\n");

                        encoded.push_str(datum);

                        encoded.push_str("\r\n");

                        encoded
                    }
                },
            },

            &Value::Array(ref inner) => match inner {
                &None => Value::ENCODED_NULL_ARRAY.to_owned(),

                &Some(ref data) => match data.len() {
                    0 => Value::ENCODED_EMPTY_ARRAY.to_owned(),

                    len => {
                        let len_str = len.to_string();

                        let mut encoded_len = len_str.len() + 3;

                        let encoded_values: Vec<String> = {
                            data.iter()
                                .map(|value| {
                                    let encoded = value.encode();

                                    encoded_len += encoded.len();

                                    encoded
                                })
                                .collect()
                        };

                        let mut encoded = String::with_capacity(encoded_len);

                        encoded.push('*');

                        encoded.push_str(&len_str);

                        encoded.push_str("\r\n");

                        encoded.push_str(&encoded_values.concat());

                        encoded
                    }
                },
            },
        }
    }

    /// Encodes a `Value` as a vector of bytes.
    ///
    /// # Examples
    ///
    /// ```
    /// use lib_resp::Value;
    ///
    /// let error = Value::err("ERR");
    ///
    /// assert_eq!(&error.encode_bytes(), b"-ERR\r\n");
    /// ```
    #[inline(always)]
    pub fn encode_bytes(&self) -> Vec<u8> {
        self.encode().into_bytes()
    }

    /// Checks if a `Value` is null.
    ///
    /// NOTE: Only the `Array` and `BStr` types can represent a null value.
    ///
    /// # Examples
    ///
    /// ```
    /// use lib_resp::Value;
    ///
    /// let name = Value::BStr(None);
    ///
    /// assert!(name.is_null());
    /// ```
    ///
    /// ```
    /// use lib_resp::Value;
    ///
    /// let name = Value::b_str(Some("Josh"));
    ///
    /// assert!(!name.is_null());
    /// ```
    #[inline]
    pub fn is_null(&self) -> bool {
        match self {
            &Value::Array(None) | &Value::BStr(None) => true,

            // No other types can represent null values
            _ => false,
        }
    }

    /// Checks is a `Value` is empty.
    ///
    /// # Examples
    ///
    /// ```
    /// use lib_resp::Value;
    ///
    /// let error = Value::err("");
    ///
    /// assert!(error.is_empty());
    /// ```
    ///
    /// ```
    /// use lib_resp::Value;
    ///
    /// let error = Value::err("ERR");
    ///
    /// assert!(!error.is_empty())
    /// ```
    ///
    /// Null values count as empty too:
    ///
    /// ```
    /// use lib_resp::Value;
    ///
    /// let name = Value::BStr(None);
    ///
    /// assert!(name.is_empty());
    /// ```
    #[inline]
    pub fn is_empty(&self) -> bool {
        match self {
            &Value::Int(_) => false,

            &Value::Str(ref value) | &Value::Err(ref value) => value.is_empty(),

            &Value::BStr(ref inner) => match inner {
                &None => true,

                &Some(ref value) => value.is_empty(),
            },

            &Value::Array(ref inner) => match inner {
                &None => true,

                &Some(ref items) => items.is_empty(),
            },
        }
    }

    /// Constructs a new integer value.
    ///
    /// NOTE: Using this function has no benefits, it's simply here for completeness.
    ///
    /// # Examples
    ///
    /// ```
    /// use lib_resp::Value;
    ///
    /// let age = Value::int(-3);
    ///
    /// println!("{:?}", age);
    /// ```
    #[inline(always)]
    pub fn int(value: i64) -> Self {
        Value::Int(value)
    }

    /// Constructs a new simple string.
    ///
    /// # Examples
    ///
    /// ```
    /// use lib_resp::Value;
    ///
    /// let status = Value::str("OK");
    ///
    /// println!("{:?}", status);
    /// ```
    #[inline(always)]
    pub fn str<T>(value: T) -> Self
    where
        T: ToString,
    {
        Value::Str(value.to_string())
    }

    /// Constructs a new error.
    ///
    /// # Examples
    ///
    /// ```
    /// use lib_resp::Value;
    ///
    /// let err = Value::err("ERR");
    ///
    /// println!("{:?}", err);
    /// ```
    #[inline(always)]
    pub fn err<T>(error: T) -> Self
    where
        T: ToString,
    {
        Value::Err(error.to_string())
    }

    #[inline(always)]
    pub fn b_str<T>(value: Option<T>) -> Self
    where
        T: ToString,
    {
        Value::BStr(value.map(|v| v.to_string()))
    }

    /// Constructs a new array value.
    ///
    /// NOTE: Using this function has no benefits, it's simply here for completeness.
    ///
    /// # Examples
    ///
    /// ```
    /// use lib_resp::Value;
    ///
    /// let users = Value::array(Some(vec![
    ///     Value::b_str(Some("foo")),
    ///     Value::b_str(Some("bar")),
    ///     Value::b_str(Some("baz"))
    /// ]));
    ///
    /// println!("{:?}", users);
    /// ```
    #[inline(always)]
    pub fn array(values: Option<Vec<Value>>) -> Self {
        Value::Array(values)
    }
}

impl Debug for Value {
    fn fmt(&self, f: &mut Formatter) -> FmtResult {
        match self {
            &Value::Int(ref datum) => write!(f, "Int({})", datum),

            &Value::Str(ref datum) => write!(f, r#"Str("{}")"#, datum),

            &Value::Err(ref datum) => write!(f, r#"Err("{}")"#, datum),

            &Value::BStr(ref value) => match value {
                &None => write!(f, "BStr(None)"),

                &Some(ref datum) => match datum.len() {
                    0 => write!(f, "BStr(0)"),

                    len => write!(f, r#"BStr({}, "{}")"#, len, datum),
                },
            },

            &Value::Array(ref value) => {
                write!(f, "Array[")?;

                match value {
                    &Some(ref data) => {
                        write!(f, "{}](", data.len())?;

                        for (i, datum) in data.iter().enumerate() {
                            write!(f, "{:?}", datum)?;

                            if data.len() - 1 > i {
                                write!(f, ", ")?;
                            }
                        }

                        write!(f, ")")
                    }

                    &None => write!(f, "-1]"),
                }
            }
        }
    }
}

impl Display for Value {
    fn fmt(&self, f: &mut Formatter) -> FmtResult {
        match self {
            &Value::Int(ref datum) => write!(f, "(integer) {}", datum),

            &Value::Str(ref datum) => write!(f, "{}", datum),

            &Value::Err(ref datum) => write!(f, "(error) {}", datum),

            &Value::BStr(ref value) => match value {
                &Some(ref datum) => write!(f, r#""{}""#, datum),

                &None => write!(f, r#""""#),
            },

            &Value::Array(ref value) => match value {
                &Some(ref data) => {
                    for (i, datum) in data.iter().enumerate() {
                        let n = i + 1;

                        write!(f, "{}) {}", n, datum)?;

                        if n < data.len() {
                            write!(f, "\r\n")?;
                        }
                    }

                    Ok(())
                }

                &None => write!(f, "(empty list or set)"),
            },
        }
    }
}

impl From<i64> for Value {
    fn from(value: i64) -> Self {
        Value::int(value)
    }
}