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use crate::ByteError;

use alloc::fmt::{self, Display, Formatter};

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
/// The unit of bytes.
pub enum ByteUnit {
    /// 1 B = 1 byte
    B,
    /// 1 KB = 1000 bytes
    KB,
    /// 1 KiB = 1024 bytes
    KiB,
    /// 1 MB = 1000000 bytes
    MB,
    /// 1 MiB = 1048576 bytes
    MiB,
    /// 1 GB = 1000000000 bytes
    GB,
    /// 1 GiB = 1073741824 bytes
    GiB,
    /// 1 TB = 1000000000000 bytes
    TB,
    /// 1 TiB = 1099511627776 bytes
    TiB,
    /// 1 PB = 1000000000000000 bytes
    PB,
    /// 1 PiB = 1125899906842624 bytes
    PiB,
}

impl Display for ByteUnit {
    #[inline]
    fn fmt(&self, f: &mut Formatter) -> Result<(), fmt::Error> {
        f.write_str(self.as_ref())
    }
}

impl AsRef<str> for ByteUnit {
    #[inline]
    fn as_ref(&self) -> &str {
        self.as_str()
    }
}

impl ByteUnit {
    /// Get an instance of `ByteUnit` from a string slice.
    ///
    /// ```
    /// extern crate byte_unit;
    ///
    /// use byte_unit::ByteUnit;
    ///
    /// assert_eq!(ByteUnit::B, ByteUnit::from_str("").unwrap());
    /// assert_eq!(ByteUnit::B, ByteUnit::from_str("b").unwrap());
    /// assert_eq!(ByteUnit::B, ByteUnit::from_str("B").unwrap());
    /// assert_eq!(ByteUnit::KB, ByteUnit::from_str("k").unwrap());
    /// assert_eq!(ByteUnit::KB, ByteUnit::from_str("K").unwrap());
    /// assert_eq!(ByteUnit::KiB, ByteUnit::from_str("Kib").unwrap());
    /// assert_eq!(ByteUnit::MB, ByteUnit::from_str("mb").unwrap());
    /// assert_eq!(ByteUnit::MiB, ByteUnit::from_str("mib").unwrap());
    /// assert_eq!(ByteUnit::GB, ByteUnit::from_str("GB").unwrap());
    /// assert_eq!(ByteUnit::GiB, ByteUnit::from_str("GiB").unwrap());
    /// assert_eq!(ByteUnit::TB, ByteUnit::from_str("TB").unwrap());
    /// assert_eq!(ByteUnit::TiB, ByteUnit::from_str("TIB").unwrap());
    /// assert_eq!(ByteUnit::PB, ByteUnit::from_str("PB").unwrap());
    /// assert_eq!(ByteUnit::PiB, ByteUnit::from_str("PiB").unwrap());
    /// ```
    pub fn from_str<S: AsRef<str>>(unit: S) -> Result<ByteUnit, ByteError> {
        let s = unit.as_ref().trim();

        let mut chars = s.chars();

        match chars.next() {
            Some(c) => {
                match c.to_ascii_uppercase() {
                    'B' => if let Some(_) = chars.next() {
                        Err(ByteError::UnitIncorrect(format!("The character {:?} is incorrect. No character is expected.", c)))
                    } else {
                        Ok(ByteUnit::B)
                    }
                    'K' => match chars.next() {
                        Some(c) => match c.to_ascii_uppercase() {
                            'I' => match chars.next() {
                                Some(c) => match c.to_ascii_uppercase() {
                                    'B' => Ok(ByteUnit::KiB),
                                    _ => Err(ByteError::UnitIncorrect(format!("The character {:?} is incorrect. A 'B' is expected.", c)))
                                }
                                None => Ok(ByteUnit::KiB)
                            }
                            'B' => if let Some(_) = chars.next() {
                                Err(ByteError::UnitIncorrect(format!("The character {:?} is incorrect. No character is expected.", c)))
                            } else {
                                Ok(ByteUnit::KB)
                            }
                            _ => Err(ByteError::UnitIncorrect(format!("The character {:?} is incorrect. A 'B' or an 'i' is expected.", c)))
                        }
                        None => Ok(ByteUnit::KB)
                    }
                    'M' => match chars.next() {
                        Some(c) => match c.to_ascii_uppercase() {
                            'I' => match chars.next() {
                                Some(c) => match c.to_ascii_uppercase() {
                                    'B' => Ok(ByteUnit::MiB),
                                    _ => Err(ByteError::UnitIncorrect(format!("The character {:?} is incorrect. A 'B' is expected.", c)))
                                }
                                None => Ok(ByteUnit::MiB)
                            }
                            'B' => if let Some(_) = chars.next() {
                                Err(ByteError::UnitIncorrect(format!("The character {:?} is incorrect. No character is expected.", c)))
                            } else {
                                Ok(ByteUnit::MB)
                            },
                            _ => Err(ByteError::UnitIncorrect(format!("The character {:?} is incorrect. A 'B' or an 'i' is expected.", c)))
                        }
                        None => Ok(ByteUnit::MB)
                    },
                    'G' => match chars.next() {
                        Some(c) => match c.to_ascii_uppercase() {
                            'I' => match chars.next() {
                                Some(c) => match c.to_ascii_uppercase() {
                                    'B' => Ok(ByteUnit::GiB),
                                    _ => Err(ByteError::UnitIncorrect(format!("The character {:?} is incorrect. A 'B' is expected.", c)))
                                }
                                None => Ok(ByteUnit::GiB)
                            }
                            'B' => if let Some(_) = chars.next() {
                                Err(ByteError::UnitIncorrect(format!("The character {:?} is incorrect. No character is expected.", c)))
                            } else {
                                Ok(ByteUnit::GB)
                            },
                            _ => Err(ByteError::UnitIncorrect(format!("The character {:?} is incorrect. A 'B' or an 'i' is expected.", c)))
                        }
                        None => Ok(ByteUnit::GB)
                    },
                    'T' => match chars.next() {
                        Some(c) => match c.to_ascii_uppercase() {
                            'I' => match chars.next() {
                                Some(c) => match c.to_ascii_uppercase() {
                                    'B' => Ok(ByteUnit::TiB),
                                    _ => Err(ByteError::UnitIncorrect(format!("The character {:?} is incorrect. A 'B' is expected.", c)))
                                }
                                None => {
                                    Ok(ByteUnit::TiB)
                                }
                            }
                            'B' => if let Some(_) = chars.next() {
                                Err(ByteError::UnitIncorrect(format!("The character {:?} is incorrect. No character is expected.", c)))
                            } else {
                                Ok(ByteUnit::TB)
                            },
                            _ => Err(ByteError::UnitIncorrect(format!("The character {:?} is incorrect. A 'B' or an 'i' is expected.", c)))
                        }
                        None => Ok(ByteUnit::TB)
                    },
                    'P' => match chars.next() {
                        Some(c) => match c.to_ascii_uppercase() {
                            'I' => match chars.next() {
                                Some(c) => match c.to_ascii_uppercase() {
                                    'B' => Ok(ByteUnit::PiB),
                                    _ => Err(ByteError::UnitIncorrect(format!("The character {:?} is incorrect. A 'B' is expected.", c)))
                                }
                                None => Ok(ByteUnit::PiB)
                            }
                            'B' => if let Some(_) = chars.next() {
                                Err(ByteError::UnitIncorrect(format!("The character {:?} is incorrect. No character is expected.", c)))
                            } else {
                                Ok(ByteUnit::PB)
                            },
                            _ => Err(ByteError::UnitIncorrect(format!("The character {:?} is incorrect. A 'B' or an 'i' is expected.", c)))
                        }
                        None => Ok(ByteUnit::PB)
                    },
                    _ => Err(ByteError::UnitIncorrect(format!("The character {:?} is incorrect. A 'B', a 'K', a 'M', a 'G', a 'T', a 'P' or no character is expected.", c)))
                }
            }
            None => Ok(ByteUnit::B)
        }
    }

    /// Use string slice to represent this `ByteUnit`.
    ///
    /// ```
    /// extern crate byte_unit;
    ///
    /// use byte_unit::ByteUnit;
    ///
    /// assert_eq!("B", ByteUnit::B.as_str());
    /// assert_eq!("KB", ByteUnit::KB.as_str());
    /// assert_eq!("KiB", ByteUnit::KiB.as_str());
    /// assert_eq!("MB", ByteUnit::MB.as_str());
    /// assert_eq!("MiB", ByteUnit::MiB.as_str());
    /// assert_eq!("GB", ByteUnit::GB.as_str());
    /// assert_eq!("GiB", ByteUnit::GiB.as_str());
    /// assert_eq!("TB", ByteUnit::TB.as_str());
    /// assert_eq!("TiB", ByteUnit::TiB.as_str());
    /// assert_eq!("PB", ByteUnit::PB.as_str());
    /// assert_eq!("PiB", ByteUnit::PiB.as_str());
    /// ```
    #[inline]
    pub fn as_str(&self) -> &'static str {
        match self {
            ByteUnit::B => "B",
            ByteUnit::KB => "KB",
            ByteUnit::KiB => "KiB",
            ByteUnit::MB => "MB",
            ByteUnit::MiB => "MiB",
            ByteUnit::GB => "GB",
            ByteUnit::GiB => "GiB",
            ByteUnit::TB => "TB",
            ByteUnit::TiB => "TiB",
            ByteUnit::PB => "PB",
            ByteUnit::PiB => "PiB",
        }
    }
}