use borsh::{BorshDeserialize, BorshSerialize};
use std::any::Any;
use std::fmt::{self, Error, Formatter};
use std::io;

/// For bugs in the runtime itself, crash and die is the usual response.
///
/// See the doc comment on `VMResult` for an explanation what the difference
/// between this and a `FunctionCallError` is.
#[derive(Debug, thiserror::Error)]
pub enum VMRunnerError {
    /// An error that is caused by an operation on an inconsistent state.
    /// E.g. an integer overflow by using a value from the given context.
    #[error("{0}")]
    InconsistentStateError(InconsistentStateError),
    /// Error caused by caching.
    #[error("cache error: {0}")]
    CacheError(#[from] CacheError),
    /// Error (eg, resource exhausting) when loading a successfully compiled
    /// contract into executable memory.
    #[error("loading error: {0}")]
    LoadingError(String),
    /// Type erased error from `External` trait implementation.
    #[error("external error")]
    ExternalError(AnyError),
    /// Non-deterministic error.
    #[error("non-deterministic error during contract execution: {0}")]
    Nondeterministic(String),
    #[error("unknown error during contract execution: {debug_message}")]
    WasmUnknownError { debug_message: String },
}

/// Permitted errors that cause a function call to fail gracefully.
///
/// Occurrence of such errors will be included in the merklize state on chain
/// using a single bit to signal failure vs Success.
///
/// See the doc comment on `VMResult` for an explanation what the difference
/// between this and a `VMRunnerError` is. And see `PartialExecutionStatus`
/// for what gets stored on chain.
#[derive(Debug, PartialEq, Eq, strum::IntoStaticStr)]
pub enum FunctionCallError {
    /// Wasm compilation error
    CompilationError(CompilationError),
    /// Wasm binary env link error
    LinkError {
        msg: String,
    },
    /// Import/export resolve error
    MethodResolveError(MethodResolveError),
    /// A trap happened during execution of a binary
    WasmTrap(WasmTrap),
    HostError(HostError),
}

#[derive(Debug, thiserror::Error, strum::IntoStaticStr)]
pub enum CacheError {
    #[error("cache read error")]
    ReadError(#[source] io::Error),
    #[error("cache write error")]
    WriteError(#[source] io::Error),
    #[error("cache deserialization error")]
    DeserializationError,
    #[error("cache serialization error")]
    SerializationError { hash: [u8; 32] },
}
/// A kind of a trap happened during execution of a binary
#[derive(Debug, Clone, PartialEq, Eq, strum::IntoStaticStr)]
pub enum WasmTrap {
    /// An `unreachable` opcode was executed.
    Unreachable,
    /// Call indirect incorrect signature trap.
    IncorrectCallIndirectSignature,
    /// Memory out of bounds trap.
    MemoryOutOfBounds,
    /// Call indirect out of bounds trap.
    CallIndirectOOB,
    /// An arithmetic exception, e.g. divided by zero.
    IllegalArithmetic,
    /// Misaligned atomic access trap.
    MisalignedAtomicAccess,
    /// Indirect call to null.
    IndirectCallToNull,
    /// Stack overflow.
    StackOverflow,
    /// Generic trap.
    GenericTrap,
}

#[derive(Debug, Clone, PartialEq, Eq, strum::IntoStaticStr)]
pub enum MethodResolveError {
    MethodEmptyName,
    MethodNotFound,
    MethodInvalidSignature,
}

#[derive(Debug, Clone, PartialEq, Eq, BorshDeserialize, BorshSerialize, strum::IntoStaticStr)]
pub enum CompilationError {
    CodeDoesNotExist {
        account_id: Box<str>,
    },
    PrepareError(PrepareError),
    /// This is for defense in depth.
    /// We expect our runtime-independent preparation code to fully catch all invalid wasms,
    /// but, if it ever misses something we’ll emit this error
    WasmerCompileError {
        msg: String,
    },
}

#[derive(Debug, Clone, PartialEq, Eq, BorshDeserialize, BorshSerialize)]
/// Error that can occur while preparing or executing Wasm smart-contract.
pub enum PrepareError {
    /// Error happened while serializing the module.
    Serialization,
    /// Error happened while deserializing the module.
    Deserialization,
    /// Internal memory declaration has been found in the module.
    InternalMemoryDeclared,
    /// Gas instrumentation failed.
    ///
    /// This most likely indicates the module isn't valid.
    GasInstrumentation,
    /// Stack instrumentation failed.
    ///
    /// This  most likely indicates the module isn't valid.
    StackHeightInstrumentation,
    /// Error happened during instantiation.
    ///
    /// This might indicate that `start` function trapped, or module isn't
    /// instantiable and/or unlinkable.
    Instantiate,
    /// Error creating memory.
    Memory,
    /// Contract contains too many functions.
    TooManyFunctions,
    /// Contract contains too many locals.
    TooManyLocals,
}

#[derive(Debug, Clone, PartialEq, Eq, strum::IntoStaticStr)]
pub enum HostError {
    /// String encoding is bad UTF-16 sequence
    BadUTF16,
    /// String encoding is bad UTF-8 sequence
    BadUTF8,
    /// Exceeded the prepaid gas
    GasExceeded,
    /// Exceeded the maximum amount of gas allowed to burn per contract
    GasLimitExceeded,
    /// Exceeded the account balance
    BalanceExceeded,
    /// Tried to call an empty method name
    EmptyMethodName,
    /// Smart contract panicked
    GuestPanic { panic_msg: String },
    /// IntegerOverflow happened during a contract execution
    IntegerOverflow,
    /// `promise_idx` does not correspond to existing promises
    InvalidPromiseIndex { promise_idx: u64 },
    /// Actions can only be appended to non-joint promise.
    CannotAppendActionToJointPromise,
    /// Returning joint promise is currently prohibited
    CannotReturnJointPromise,
    /// Accessed invalid promise result index
    InvalidPromiseResultIndex { result_idx: u64 },
    /// Accessed invalid register id
    InvalidRegisterId { register_id: u64 },
    /// Accessed memory outside the bounds
    MemoryAccessViolation,
    /// VM Logic returned an invalid receipt index
    InvalidReceiptIndex { receipt_index: u64 },
    /// Iterator index `iterator_index` does not exist
    InvalidIteratorIndex { iterator_index: u64 },
    /// VM Logic returned an invalid account id
    InvalidAccountId,
    /// VM Logic returned an invalid method name
    InvalidMethodName,
    /// VM Logic provided an invalid public key
    InvalidPublicKey,
    /// `method_name` is not allowed in view calls
    ProhibitedInView { method_name: String },
    /// The total number of logs will exceed the limit.
    NumberOfLogsExceeded { limit: u64 },
    /// The storage key length exceeded the limit.
    KeyLengthExceeded { length: u64, limit: u64 },
    /// The storage value length exceeded the limit.
    ValueLengthExceeded { length: u64, limit: u64 },
    /// The total log length exceeded the limit.
    TotalLogLengthExceeded { length: u64, limit: u64 },
    /// The maximum number of promises within a FunctionCall exceeded the limit.
    NumberPromisesExceeded { number_of_promises: u64, limit: u64 },
    /// The maximum number of input data dependencies exceeded the limit.
    NumberInputDataDependenciesExceeded { number_of_input_data_dependencies: u64, limit: u64 },
    /// The returned value length exceeded the limit.
    ReturnedValueLengthExceeded { length: u64, limit: u64 },
    /// The contract size for DeployContract action exceeded the limit.
    ContractSizeExceeded { size: u64, limit: u64 },
    /// The host function was deprecated.
    Deprecated { method_name: String },
    /// General errors for ECDSA recover.
    ECRecoverError { msg: String },
    /// Invalid input to alt_bn128 familiy of functions (e.g., point which isn't
    /// on the curve).
    AltBn128InvalidInput { msg: String },
    /// Invalid input to ed25519 signature verification function (e.g. signature cannot be
    /// derived from bytes).
    Ed25519VerifyInvalidInput { msg: String },
}

#[derive(Debug, PartialEq, Eq)]
pub enum VMLogicError {
    /// Errors coming from native Wasm VM.
    HostError(HostError),
    /// Type erased error from `External` trait implementation.
    ExternalError(AnyError),
    /// An error that is caused by an operation on an inconsistent state.
    InconsistentStateError(InconsistentStateError),
}

impl std::error::Error for VMLogicError {}

/// An error that is caused by an operation on an inconsistent state, such as
/// integer overflow.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum InconsistentStateError {
    /// Math operation with a value from the state resulted in a integer overflow.
    IntegerOverflow,
}

impl From<HostError> for VMLogicError {
    fn from(err: HostError) -> Self {
        VMLogicError::HostError(err)
    }
}

impl From<InconsistentStateError> for VMLogicError {
    fn from(err: InconsistentStateError) -> Self {
        VMLogicError::InconsistentStateError(err)
    }
}

impl From<PrepareError> for FunctionCallError {
    fn from(err: PrepareError) -> Self {
        FunctionCallError::CompilationError(CompilationError::PrepareError(err))
    }
}

/// Try to convert a general error that happened at the `VMLogic` level to a
/// `FunctionCallError` that can be included in a `VMOutcome`.
///
/// `VMLogicError` have two very different types of errors. Some are just
/// a result from the guest code doing incorrect things, other are bugs in
/// framework.
/// The first type can be converted to a `FunctionCallError`, the other becomes
/// a `VMRunnerError` instead and must be treated differently.
impl TryFrom<VMLogicError> for FunctionCallError {
    type Error = VMRunnerError;
    fn try_from(err: VMLogicError) -> Result<Self, Self::Error> {
        match err {
            VMLogicError::HostError(h) => Ok(FunctionCallError::HostError(h)),
            VMLogicError::ExternalError(s) => Err(VMRunnerError::ExternalError(s)),
            VMLogicError::InconsistentStateError(e) => {
                Err(VMRunnerError::InconsistentStateError(e))
            }
        }
    }
}

impl fmt::Display for VMLogicError {
    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error> {
        write!(f, "{:?}", self)
    }
}

impl fmt::Display for PrepareError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
        use PrepareError::*;
        f.write_str(match self {
            Serialization => "Error happened while serializing the module.",
            Deserialization => "Error happened while deserializing the module.",
            InternalMemoryDeclared => "Internal memory declaration has been found in the module.",
            GasInstrumentation => "Gas instrumentation failed.",
            StackHeightInstrumentation => "Stack instrumentation failed.",
            Instantiate => "Error happened during instantiation.",
            Memory => "Error creating memory.",
            TooManyFunctions => "Too many functions in contract.",
            TooManyLocals => "Too many locals declared in the contract.",
        })
    }
}

impl fmt::Display for FunctionCallError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
        match self {
            FunctionCallError::CompilationError(e) => e.fmt(f),
            FunctionCallError::MethodResolveError(e) => e.fmt(f),
            FunctionCallError::HostError(e) => e.fmt(f),
            FunctionCallError::LinkError { msg } => write!(f, "{}", msg),
            FunctionCallError::WasmTrap(trap) => write!(f, "WebAssembly trap: {}", trap),
        }
    }
}

impl fmt::Display for WasmTrap {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
        match self {
            WasmTrap::Unreachable => write!(f, "An `unreachable` opcode was executed."),
            WasmTrap::IncorrectCallIndirectSignature => {
                write!(f, "Call indirect incorrect signature trap.")
            }
            WasmTrap::MemoryOutOfBounds => write!(f, "Memory out of bounds trap."),
            WasmTrap::CallIndirectOOB => write!(f, "Call indirect out of bounds trap."),
            WasmTrap::IllegalArithmetic => {
                write!(f, "An arithmetic exception, e.g. divided by zero.")
            }
            WasmTrap::MisalignedAtomicAccess => write!(f, "Misaligned atomic access trap."),
            WasmTrap::GenericTrap => write!(f, "Generic trap."),
            WasmTrap::StackOverflow => write!(f, "Stack overflow."),
            WasmTrap::IndirectCallToNull => write!(f, "Indirect call to null."),
        }
    }
}

impl fmt::Display for CompilationError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
        match self {
            CompilationError::CodeDoesNotExist { account_id } => {
                write!(f, "cannot find contract code for account {}", account_id)
            }
            CompilationError::PrepareError(p) => write!(f, "PrepareError: {}", p),
            CompilationError::WasmerCompileError { msg } => {
                write!(f, "Wasmer compilation error: {}", msg)
            }
        }
    }
}

impl fmt::Display for MethodResolveError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
        fmt::Debug::fmt(self, f)
    }
}

impl std::fmt::Display for InconsistentStateError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
        match self {
            InconsistentStateError::IntegerOverflow => write!(
                f,
                "Math operation with a value from the state resulted in a integer overflow.",
            ),
        }
    }
}

impl std::fmt::Display for HostError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
        use HostError::*;
        match self {
            BadUTF8 => write!(f, "String encoding is bad UTF-8 sequence."),
            BadUTF16 => write!(f, "String encoding is bad UTF-16 sequence."),
            GasExceeded => write!(f, "Exceeded the prepaid gas."),
            GasLimitExceeded => {
                write!(f, "Exceeded the maximum amount of gas allowed to burn per contract.")
            }
            BalanceExceeded => write!(f, "Exceeded the account balance."),
            EmptyMethodName => write!(f, "Tried to call an empty method name."),
            GuestPanic { panic_msg } => write!(f, "Smart contract panicked: {}", panic_msg),
            IntegerOverflow => write!(f, "Integer overflow."),
            InvalidIteratorIndex { iterator_index } => {
                write!(f, "Iterator index {:?} does not exist", iterator_index)
            }
            InvalidPromiseIndex { promise_idx } => {
                write!(f, "{:?} does not correspond to existing promises", promise_idx)
            }
            CannotAppendActionToJointPromise => {
                write!(f, "Actions can only be appended to non-joint promise.")
            }
            CannotReturnJointPromise => {
                write!(f, "Returning joint promise is currently prohibited.")
            }
            InvalidPromiseResultIndex { result_idx } => {
                write!(f, "Accessed invalid promise result index: {:?}", result_idx)
            }
            InvalidRegisterId { register_id } => {
                write!(f, "Accessed invalid register id: {:?}", register_id)
            }
            MemoryAccessViolation => write!(f, "Accessed memory outside the bounds."),
            InvalidReceiptIndex { receipt_index } => {
                write!(f, "VM Logic returned an invalid receipt index: {:?}", receipt_index)
            }
            InvalidAccountId => write!(f, "VM Logic returned an invalid account id"),
            InvalidMethodName => write!(f, "VM Logic returned an invalid method name"),
            InvalidPublicKey => write!(f, "VM Logic provided an invalid public key"),
            ProhibitedInView { method_name } => {
                write!(f, "{} is not allowed in view calls", method_name)
            }
            NumberOfLogsExceeded { limit } => {
                write!(f, "The number of logs will exceed the limit {}", limit)
            }
            KeyLengthExceeded { length, limit } => {
                write!(f, "The length of a storage key {} exceeds the limit {}", length, limit)
            }
            ValueLengthExceeded { length, limit } => {
                write!(f, "The length of a storage value {} exceeds the limit {}", length, limit)
            }
            TotalLogLengthExceeded { length, limit } => {
                write!(f, "The length of a log message {} exceeds the limit {}", length, limit)
            }
            NumberPromisesExceeded { number_of_promises, limit } => write!(
                f,
                "The number of promises within a FunctionCall {} exceeds the limit {}",
                number_of_promises, limit
            ),
            NumberInputDataDependenciesExceeded { number_of_input_data_dependencies, limit } => {
                write!(
                    f,
                    "The number of input data dependencies {} exceeds the limit {}",
                    number_of_input_data_dependencies, limit
                )
            }
            ReturnedValueLengthExceeded { length, limit } => {
                write!(f, "The length of a returned value {} exceeds the limit {}", length, limit)
            }
            ContractSizeExceeded { size, limit } => write!(
                f,
                "The size of a contract code in DeployContract action {} exceeds the limit {}",
                size, limit
            ),
            Deprecated { method_name } => {
                write!(f, "Attempted to call deprecated host function {}", method_name)
            }
            AltBn128InvalidInput { msg } => write!(f, "AltBn128 invalid input: {}", msg),
            ECRecoverError { msg } => write!(f, "ECDSA recover error: {}", msg),
            Ed25519VerifyInvalidInput { msg } => {
                write!(f, "ED25519 signature verification error: {}", msg)
            }
        }
    }
}

/// Type-erased error used to shuttle some concrete error coming from `External`
/// through vm-logic.
///
/// The caller is supposed to downcast this to a concrete error type they should
/// know. This would be just `Box<dyn Any + Eq>` if the latter actually worked.
pub struct AnyError {
    any: Box<dyn AnyEq>,
}

#[derive(Debug, thiserror::Error)]
#[error("failed to downcast")]
pub struct DowncastFailedError;

impl AnyError {
    pub fn new<E: Any + Eq + Send + Sync + 'static>(err: E) -> AnyError {
        AnyError { any: Box::new(err) }
    }
    pub fn downcast<E: Any + Eq + Send + Sync + 'static>(self) -> Result<E, DowncastFailedError> {
        match self.any.into_any().downcast::<E>() {
            Ok(it) => Ok(*it),
            Err(_) => Err(DowncastFailedError),
        }
    }
}

impl PartialEq for AnyError {
    fn eq(&self, other: &Self) -> bool {
        self.any.any_eq(&*other.any)
    }
}

impl Eq for AnyError {}

impl fmt::Debug for AnyError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Debug::fmt(self.any.as_any(), f)
    }
}

trait AnyEq: Any + Send + Sync {
    fn any_eq(&self, rhs: &dyn AnyEq) -> bool;
    fn as_any(&self) -> &dyn Any;
    fn into_any(self: Box<Self>) -> Box<dyn Any>;
}

impl<T: Any + Eq + Sized + Send + Sync> AnyEq for T {
    fn any_eq(&self, rhs: &dyn AnyEq) -> bool {
        match rhs.as_any().downcast_ref::<Self>() {
            Some(rhs) => self == rhs,
            None => false,
        }
    }
    fn as_any(&self) -> &dyn Any {
        self
    }
    fn into_any(self: Box<Self>) -> Box<dyn Any> {
        self
    }
}

#[cfg(test)]
mod tests {
    use crate::logic::errors::{
        CompilationError, FunctionCallError, MethodResolveError, PrepareError,
    };

    #[test]
    fn test_display() {
        // TODO: proper printing
        assert_eq!(
            FunctionCallError::MethodResolveError(MethodResolveError::MethodInvalidSignature)
                .to_string(),
            "MethodInvalidSignature"
        );
        assert_eq!(
            FunctionCallError::CompilationError(CompilationError::PrepareError(
                PrepareError::StackHeightInstrumentation
            ))
            .to_string(),
            "PrepareError: Stack instrumentation failed."
        );
    }
}