// Copyright (c) Facebook, Inc. and its affiliates.
// Copyright (c) Zefchain Labs, Inc.
// SPDX-License-Identifier: Apache-2.0

//! Core data-types used in the Linera protocol.

use std::{
    fmt,
    time::{Duration, SystemTime},
};

use serde::{Deserialize, Serialize};
use thiserror::Error;

use crate::{
    doc_scalar,
    identifiers::{ApplicationId, Destination, GenericApplicationId},
};

/// A non-negative amount of tokens.
///
/// This is a fixed-point fraction, with [`Amount::DECIMAL_PLACES`] digits after the point.
/// [`Amount::ONE`] is one whole token, divisible into `10.pow(Amount::DECIMAL_PLACES)` parts.
#[derive(Eq, PartialEq, Ord, PartialOrd, Copy, Clone, Hash, Default, Debug)]
pub struct Amount(u128);

#[derive(Serialize, Deserialize)]
#[serde(rename = "Amount")]
struct AmountString(String);

#[derive(Serialize, Deserialize)]
#[serde(rename = "Amount")]
struct AmountU128(u128);

impl Serialize for Amount {
    fn serialize<S: serde::ser::Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
        if serializer.is_human_readable() {
            AmountString(self.to_string()).serialize(serializer)
        } else {
            AmountU128(self.0).serialize(serializer)
        }
    }
}

impl<'de> Deserialize<'de> for Amount {
    fn deserialize<D: serde::de::Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
        if deserializer.is_human_readable() {
            let AmountString(s) = AmountString::deserialize(deserializer)?;
            s.parse().map_err(serde::de::Error::custom)
        } else {
            Ok(Amount(AmountU128::deserialize(deserializer)?.0))
        }
    }
}

/// A block height to identify blocks in a chain.
#[derive(
    Eq, PartialEq, Ord, PartialOrd, Copy, Clone, Hash, Default, Debug, Serialize, Deserialize,
)]
#[cfg_attr(with_testing, derive(test_strategy::Arbitrary))]
pub struct BlockHeight(pub u64);

/// An identifier for successive attempts to decide a value in a consensus protocol.
#[derive(
    Eq, PartialEq, Ord, PartialOrd, Copy, Clone, Hash, Default, Debug, Serialize, Deserialize,
)]
pub enum Round {
    /// The initial fast round.
    #[default]
    Fast,
    /// The N-th multi-leader round.
    MultiLeader(u32),
    /// The N-th single-leader round.
    SingleLeader(u32),
}

/// A timestamp, in microseconds since the Unix epoch.
#[derive(
    Eq, PartialEq, Ord, PartialOrd, Copy, Clone, Hash, Default, Debug, Serialize, Deserialize,
)]
pub struct Timestamp(u64);

impl Timestamp {
    /// Returns the current time according to the system clock.
    pub fn now() -> Timestamp {
        Timestamp(
            SystemTime::UNIX_EPOCH
                .elapsed()
                .expect("system time should be after Unix epoch")
                .as_micros()
                .try_into()
                .unwrap_or(u64::MAX),
        )
    }

    /// Returns the number of microseconds since the Unix epoch.
    pub fn micros(&self) -> u64 {
        self.0
    }

    /// Returns the number of microseconds from `other` until `self`, or `0` if `other` is not
    /// earlier than `self`.
    pub fn saturating_diff_micros(&self, other: Timestamp) -> u64 {
        self.0.saturating_sub(other.0)
    }

    /// Returns the `Duration` between `other` and `self`, or `0` if `other` is not earlier than
    /// `self`.
    pub fn duration_since(&self, other: Timestamp) -> Duration {
        Duration::from_micros(self.saturating_diff_micros(other))
    }

    /// Returns the timestamp that is `duration` later than `self`.
    pub fn saturating_add(&self, duration: Duration) -> Timestamp {
        let micros = u64::try_from(duration.as_micros()).unwrap_or(u64::MAX);
        Timestamp(self.0.saturating_add(micros))
    }

    /// Returns a timestamp `micros` microseconds later than `self`, or the highest possible value
    /// if it would overflow.
    pub fn saturating_add_micros(&self, micros: u64) -> Timestamp {
        Timestamp(self.0.saturating_add(micros))
    }

    /// Returns a timestamp `micros` microseconds earlier than `self`, or the lowest possible value
    /// if it would underflow.
    pub fn saturating_sub_micros(&self, micros: u64) -> Timestamp {
        Timestamp(self.0.saturating_sub(micros))
    }
}

impl From<u64> for Timestamp {
    fn from(t: u64) -> Timestamp {
        Timestamp(t)
    }
}

impl fmt::Display for Timestamp {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        if let Some(date_time) = chrono::DateTime::from_timestamp(
            (self.0 / 1_000_000) as i64,
            ((self.0 % 1_000_000) * 1_000) as u32,
        ) {
            return date_time.naive_utc().fmt(f);
        }
        self.0.fmt(f)
    }
}

/// Resources that an application may spend during the execution of transaction or an
/// application call.
#[derive(Clone, Copy, Debug, Default, Deserialize, Eq, PartialEq, Serialize)]
pub struct Resources {
    /// An amount of execution fuel.
    pub fuel: u64,
    /// A number of read operations to be executed.
    pub read_operations: u32,
    /// A number of write operations to be executed.
    pub write_operations: u32,
    /// A number of bytes to read.
    pub bytes_to_read: u32,
    /// A number of bytes to write.
    pub bytes_to_write: u32,
    /// A number of messages to be sent.
    pub messages: u32,
    /// The size of the messages to be sent.
    // TODO(#1531): Account for the type of message to be sent.
    pub message_size: u32,
    /// An increase in the amount of storage space.
    pub storage_size_delta: u32,
    // TODO(#1532): Account for the system calls that we plan on calling.
    // TODO(#1533): Allow declaring calls to other applications instead of having to count them here.
}

/// A request to send a message.
#[derive(Clone, Debug, Deserialize, Serialize)]
#[cfg_attr(with_testing, derive(Eq, PartialEq))]
pub struct SendMessageRequest<Message> {
    /// The destination of the message.
    pub destination: Destination,
    /// Whether the message is authenticated.
    pub authenticated: bool,
    /// Whether the message is tracked.
    pub is_tracked: bool,
    /// The grant resources forwarded with the message.
    pub grant: Resources,
    /// The message itself.
    pub message: Message,
}

impl<Message> SendMessageRequest<Message>
where
    Message: Serialize,
{
    /// Serializes the internal `Message` type into raw bytes.
    pub fn into_raw(self) -> SendMessageRequest<Vec<u8>> {
        let message = bcs::to_bytes(&self.message).expect("Failed to serialize message");

        SendMessageRequest {
            destination: self.destination,
            authenticated: self.authenticated,
            is_tracked: self.is_tracked,
            grant: self.grant,
            message,
        }
    }
}

/// An error type for arithmetic errors.
#[derive(Debug, Error)]
#[allow(missing_docs)]
pub enum ArithmeticError {
    #[error("Number overflow")]
    Overflow,
    #[error("Number underflow")]
    Underflow,
}

macro_rules! impl_wrapped_number {
    ($name:ident, $wrapped:ident) => {
        impl $name {
            /// The zero value.
            pub const ZERO: Self = Self(0);

            /// The maximum value.
            pub const MAX: Self = Self($wrapped::MAX);

            /// Checked addition.
            pub fn try_add(self, other: Self) -> Result<Self, ArithmeticError> {
                let val = self
                    .0
                    .checked_add(other.0)
                    .ok_or(ArithmeticError::Overflow)?;
                Ok(Self(val))
            }

            /// Checked increment.
            pub fn try_add_one(self) -> Result<Self, ArithmeticError> {
                let val = self.0.checked_add(1).ok_or(ArithmeticError::Overflow)?;
                Ok(Self(val))
            }

            /// Saturating addition.
            pub fn saturating_add(self, other: Self) -> Self {
                let val = self.0.saturating_add(other.0);
                Self(val)
            }

            /// Checked subtraction.
            pub fn try_sub(self, other: Self) -> Result<Self, ArithmeticError> {
                let val = self
                    .0
                    .checked_sub(other.0)
                    .ok_or(ArithmeticError::Underflow)?;
                Ok(Self(val))
            }

            /// Checked decrement.
            pub fn try_sub_one(self) -> Result<Self, ArithmeticError> {
                let val = self.0.checked_sub(1).ok_or(ArithmeticError::Underflow)?;
                Ok(Self(val))
            }

            /// Saturating subtraction.
            pub fn saturating_sub(self, other: Self) -> Self {
                let val = self.0.saturating_sub(other.0);
                Self(val)
            }

            /// Checked in-place addition.
            pub fn try_add_assign(&mut self, other: Self) -> Result<(), ArithmeticError> {
                self.0 = self
                    .0
                    .checked_add(other.0)
                    .ok_or(ArithmeticError::Overflow)?;
                Ok(())
            }

            /// Checked in-place increment.
            pub fn try_add_assign_one(&mut self) -> Result<(), ArithmeticError> {
                self.0 = self.0.checked_add(1).ok_or(ArithmeticError::Overflow)?;
                Ok(())
            }

            /// Saturating in-place addition.
            pub fn saturating_add_assign(&mut self, other: Self) {
                self.0 = self.0.saturating_add(other.0);
            }

            /// Checked in-place subtraction.
            pub fn try_sub_assign(&mut self, other: Self) -> Result<(), ArithmeticError> {
                self.0 = self
                    .0
                    .checked_sub(other.0)
                    .ok_or(ArithmeticError::Underflow)?;
                Ok(())
            }

            /// Saturating multiplication.
            pub fn saturating_mul(&self, other: $wrapped) -> Self {
                Self(self.0.saturating_mul(other))
            }

            /// Checked multiplication.
            pub fn try_mul(self, other: $wrapped) -> Result<Self, ArithmeticError> {
                let val = self.0.checked_mul(other).ok_or(ArithmeticError::Overflow)?;
                Ok(Self(val))
            }

            /// Checked in-place multiplication.
            pub fn try_mul_assign(&mut self, other: $wrapped) -> Result<(), ArithmeticError> {
                self.0 = self.0.checked_mul(other).ok_or(ArithmeticError::Overflow)?;
                Ok(())
            }
        }

        impl From<$name> for $wrapped {
            fn from(value: $name) -> Self {
                value.0
            }
        }

        // Cannot directly create values for a wrapped type, except for testing.
        #[cfg(with_testing)]
        impl From<$wrapped> for $name {
            fn from(value: $wrapped) -> Self {
                Self(value)
            }
        }

        #[cfg(with_testing)]
        impl std::ops::Add for $name {
            type Output = Self;

            fn add(self, other: Self) -> Self {
                Self(self.0 + other.0)
            }
        }

        #[cfg(with_testing)]
        impl std::ops::Sub for $name {
            type Output = Self;

            fn sub(self, other: Self) -> Self {
                Self(self.0 - other.0)
            }
        }

        #[cfg(with_testing)]
        impl std::ops::Mul<$wrapped> for $name {
            type Output = Self;

            fn mul(self, other: $wrapped) -> Self {
                Self(self.0 * other)
            }
        }
    };
}

impl TryFrom<BlockHeight> for usize {
    type Error = ArithmeticError;

    fn try_from(height: BlockHeight) -> Result<usize, ArithmeticError> {
        usize::try_from(height.0).map_err(|_| ArithmeticError::Overflow)
    }
}

#[cfg(not(with_testing))]
impl From<u64> for BlockHeight {
    fn from(value: u64) -> Self {
        Self(value)
    }
}

impl_wrapped_number!(Amount, u128);
impl_wrapped_number!(BlockHeight, u64);

impl fmt::Display for Amount {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        // Print the wrapped integer, padded with zeros to cover a digit before the decimal point.
        let places = Amount::DECIMAL_PLACES as usize;
        let min_digits = places + 1;
        let decimals = format!("{:0min_digits$}", self.0);
        let integer_part = &decimals[..(decimals.len() - places)];
        let fractional_part = decimals[(decimals.len() - places)..].trim_end_matches('0');

        // For now, we never trim non-zero digits so we don't lose any precision.
        let precision = f.precision().unwrap_or(0).max(fractional_part.len());
        let sign = if f.sign_plus() && self.0 > 0 { "+" } else { "" };
        // The amount of padding: desired width minus sign, point and number of digits.
        let pad_width = f.width().map_or(0, |w| {
            w.saturating_sub(precision)
                .saturating_sub(sign.len() + integer_part.len() + 1)
        });
        let left_pad = match f.align() {
            None | Some(fmt::Alignment::Right) => pad_width,
            Some(fmt::Alignment::Center) => pad_width / 2,
            Some(fmt::Alignment::Left) => 0,
        };

        for _ in 0..left_pad {
            write!(f, "{}", f.fill())?;
        }
        write!(f, "{sign}{integer_part}.{fractional_part:0<precision$}")?;
        for _ in left_pad..pad_width {
            write!(f, "{}", f.fill())?;
        }
        Ok(())
    }
}

#[derive(Error, Debug)]
#[allow(missing_docs)]
pub enum ParseAmountError {
    #[error("cannot parse amount")]
    Parse,
    #[error("cannot represent amount: number too high")]
    TooHigh,
    #[error("cannot represent amount: too many decimal places after the point")]
    TooManyDigits,
}

impl std::str::FromStr for Amount {
    type Err = ParseAmountError;

    fn from_str(src: &str) -> Result<Self, Self::Err> {
        let mut result: u128 = 0;
        let mut decimals: Option<u8> = None;
        let mut chars = src.trim().chars().peekable();
        if chars.peek() == Some(&'+') {
            chars.next();
        }
        for char in chars {
            match char {
                '_' => {}
                '.' if decimals.is_some() => return Err(ParseAmountError::Parse),
                '.' => decimals = Some(Amount::DECIMAL_PLACES),
                char => {
                    let digit = u128::from(char.to_digit(10).ok_or(ParseAmountError::Parse)?);
                    if let Some(d) = &mut decimals {
                        *d = d.checked_sub(1).ok_or(ParseAmountError::TooManyDigits)?;
                    }
                    result = result
                        .checked_mul(10)
                        .and_then(|r| r.checked_add(digit))
                        .ok_or(ParseAmountError::TooHigh)?;
                }
            }
        }
        result = result
            .checked_mul(10u128.pow(decimals.unwrap_or(Amount::DECIMAL_PLACES) as u32))
            .ok_or(ParseAmountError::TooHigh)?;
        Ok(Amount(result))
    }
}

impl fmt::Display for BlockHeight {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.0.fmt(f)
    }
}

impl std::str::FromStr for BlockHeight {
    type Err = std::num::ParseIntError;

    fn from_str(src: &str) -> Result<Self, Self::Err> {
        Ok(Self(u64::from_str(src)?))
    }
}

impl fmt::Display for Round {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Round::Fast => write!(f, "fast round"),
            Round::MultiLeader(r) => write!(f, "multi-leader round {}", r),
            Round::SingleLeader(r) => write!(f, "single-leader round {}", r),
        }
    }
}

impl Round {
    /// Whether the round is a multi-leader round.
    pub fn is_multi_leader(&self) -> bool {
        matches!(self, Round::MultiLeader(_))
    }

    /// Whether the round is the fast round.
    pub fn is_fast(&self) -> bool {
        matches!(self, Round::Fast)
    }

    /// The index of a round amongst the rounds of the same category.
    pub fn number(&self) -> u32 {
        match self {
            Round::Fast => 0,
            Round::MultiLeader(r) | Round::SingleLeader(r) => *r,
        }
    }

    /// The category of the round as a string.
    pub fn type_name(&self) -> &'static str {
        match self {
            Round::Fast => "fast",
            Round::MultiLeader(_) => "multi",
            Round::SingleLeader(_) => "single",
        }
    }
}

impl<'a> std::iter::Sum<&'a Amount> for Amount {
    fn sum<I: Iterator<Item = &'a Self>>(iter: I) -> Self {
        iter.fold(Self::ZERO, |a, b| a.saturating_add(*b))
    }
}

impl Amount {
    /// The base-10 exponent representing how much a token can be divided.
    pub const DECIMAL_PLACES: u8 = 18;

    /// One token.
    pub const ONE: Amount = Amount(10u128.pow(Amount::DECIMAL_PLACES as u32));

    /// Returns an `Amount` corresponding to that many tokens, or `Amount::MAX` if saturated.
    pub fn from_tokens(tokens: u128) -> Amount {
        Self::ONE.saturating_mul(tokens)
    }

    /// Returns an `Amount` corresponding to that many millitokens, or `Amount::MAX` if saturated.
    pub fn from_millis(millitokens: u128) -> Amount {
        Amount(10u128.pow(Amount::DECIMAL_PLACES as u32 - 3)).saturating_mul(millitokens)
    }

    /// Returns an `Amount` corresponding to that many microtokens, or `Amount::MAX` if saturated.
    pub fn from_micros(microtokens: u128) -> Amount {
        Amount(10u128.pow(Amount::DECIMAL_PLACES as u32 - 6)).saturating_mul(microtokens)
    }

    /// Returns an `Amount` corresponding to that many nanotokens, or `Amount::MAX` if saturated.
    pub fn from_nanos(nanotokens: u128) -> Amount {
        Amount(10u128.pow(Amount::DECIMAL_PLACES as u32 - 9)).saturating_mul(nanotokens)
    }

    /// Returns an `Amount` corresponding to that many attotokens.
    pub fn from_attos(attotokens: u128) -> Amount {
        Amount(attotokens)
    }

    /// Helper function to obtain the 64 most significant bits of the balance.
    pub fn upper_half(self) -> u64 {
        (self.0 >> 64) as u64
    }

    /// Helper function to obtain the 64 least significant bits of the balance.
    pub fn lower_half(self) -> u64 {
        self.0 as u64
    }

    /// Divides this by the other amount. If the other is 0, it returns `u128::MAX`.
    pub fn saturating_div(self, other: Amount) -> u128 {
        self.0.checked_div(other.0).unwrap_or(u128::MAX)
    }
}

/// Permissions for applications on a chain.
#[derive(Default, Debug, PartialEq, Eq, Hash, Clone, Serialize, Deserialize)]
pub struct ApplicationPermissions {
    /// If this is `None`, all system operations and application operations are allowed.
    /// If it is `Some`, only operations from the specified applications are allowed, and
    /// no system operations.
    pub execute_operations: Option<Vec<ApplicationId>>,
    /// These applications are allowed to close the current chain using the system API.
    pub close_chain: Vec<ApplicationId>,
}

impl ApplicationPermissions {
    /// Creates new `ApplicationPermissions` where the given application is the only one
    /// whose operations are allowed, and it can also close the chain.
    pub fn new_single(app_id: ApplicationId) -> Self {
        Self {
            execute_operations: Some(vec![app_id]),
            close_chain: vec![app_id],
        }
    }

    /// Returns whether operations with the given application ID are allowed on this chain.
    pub fn can_execute_operations(&self, app_id: &GenericApplicationId) -> bool {
        match (app_id, &self.execute_operations) {
            (_, None) => true,
            (GenericApplicationId::System, Some(_)) => false,
            (GenericApplicationId::User(app_id), Some(app_ids)) => app_ids.contains(app_id),
        }
    }

    /// Returns whether the given application is allowed to close this chain.
    pub fn can_close_chain(&self, app_id: &ApplicationId) -> bool {
        self.close_chain.contains(app_id)
    }
}

doc_scalar!(Amount, "A non-negative amount of tokens.");
doc_scalar!(BlockHeight, "A block height to identify blocks in a chain");
doc_scalar!(
    Timestamp,
    "A timestamp, in microseconds since the Unix epoch"
);
doc_scalar!(
    Round,
    "A number to identify successive attempts to decide a value in a consensus protocol."
);

#[cfg(test)]
mod tests {
    use std::str::FromStr;

    use super::Amount;

    #[test]
    fn display_amount() {
        assert_eq!("1.", Amount::ONE.to_string());
        assert_eq!("1.", Amount::from_str("1.").unwrap().to_string());
        assert_eq!(
            Amount(10_000_000_000_000_000_000),
            Amount::from_str("10").unwrap()
        );
        assert_eq!("10.", Amount(10_000_000_000_000_000_000).to_string(),);
        assert_eq!(
            "1001.3",
            (Amount::from_str("1.1")
                .unwrap()
                .saturating_add(Amount::from_str("1_000.2").unwrap()))
            .to_string()
        );
        assert_eq!(
            "   1.00000000000000000000",
            format!("{:25.20}", Amount::ONE)
        );
        assert_eq!(
            "~+12.34~~",
            format!("{:~^+9.1}", Amount::from_str("12.34").unwrap())
        );
    }
}