// Copyright 2019-2022 Parity Technologies (UK) Ltd.
// This file is dual-licensed as Apache-2.0 or GPL-3.0.
// see LICENSE for license details.

//! Types representing the errors that can be returned.

use crate::metadata::Metadata;
use codec::Decode;
use core::fmt::Debug;
use scale_info::TypeDef;
use std::borrow::Cow;

// Re-expose the errors we use from other crates here:
pub use crate::metadata::{
    InvalidMetadataError,
    MetadataError,
};
pub use scale_value::scale::{
    DecodeError,
    EncodeError,
};

/// The underlying error enum, generic over the type held by the `Runtime`
/// variant. Prefer to use the [`Error<E>`] and [`Error`] aliases over
/// using this type directly.
#[derive(Debug, thiserror::Error)]
pub enum Error {
    /// Io error.
    #[error("Io error: {0}")]
    Io(#[from] std::io::Error),
    /// Codec error.
    #[error("Scale codec error: {0}")]
    Codec(#[from] codec::Error),
    /// Rpc error.
    #[error("Rpc error: {0}")]
    Rpc(#[from] RpcError),
    /// Serde serialization error
    #[error("Serde json error: {0}")]
    Serialization(#[from] serde_json::error::Error),
    /// Invalid metadata error
    #[error("Invalid Metadata: {0}")]
    InvalidMetadata(#[from] InvalidMetadataError),
    /// Invalid metadata error
    #[error("Metadata: {0}")]
    Metadata(#[from] MetadataError),
    /// Runtime error.
    #[error("Runtime error: {0:?}")]
    Runtime(DispatchError),
    /// Error decoding to a [`crate::dynamic::Value`].
    #[error("Error decoding into dynamic value: {0}")]
    DecodeValue(#[from] DecodeError),
    /// Error encoding from a [`crate::dynamic::Value`].
    #[error("Error encoding from dynamic value: {0}")]
    EncodeValue(#[from] EncodeError<()>),
    /// Transaction progress error.
    #[error("Transaction error: {0}")]
    Transaction(#[from] TransactionError),
    /// Block related error.
    #[error("Block error: {0}")]
    Block(#[from] BlockError),
    /// An error encoding a storage address.
    #[error("Error encoding storage address: {0}")]
    StorageAddress(#[from] StorageAddressError),
    /// Other error.
    #[error("Other error: {0}")]
    Other(String),
}

impl From<&str> for Error {
    fn from(error: &str) -> Self {
        Error::Other(error.into())
    }
}

impl From<String> for Error {
    fn from(error: String) -> Self {
        Error::Other(error)
    }
}

impl From<DispatchError> for Error {
    fn from(error: DispatchError) -> Self {
        Error::Runtime(error)
    }
}

/// An RPC error. Since we are generic over the RPC client that is used,
/// the error is boxed and could be casted.
#[derive(Debug, thiserror::Error)]
pub enum RpcError {
    // Dev note: We need the error to be safely sent between threads
    // for `subscribe_to_block_headers_filling_in_gaps` and friends.
    /// Error related to the RPC client.
    #[error("RPC error: {0}")]
    ClientError(Box<dyn std::error::Error + Send + Sync + 'static>),
    /// The RPC subscription dropped.
    #[error("RPC error: subscription dropped.")]
    SubscriptionDropped,
}

/// This is our attempt to decode a runtime DispatchError. We either
/// successfully decode it into a [`ModuleError`], or we fail and keep
/// hold of the bytes, which we can attempt to decode if we have an
/// appropriate static type to hand.
#[derive(Debug, thiserror::Error)]
pub enum DispatchError {
    /// An error was emitted from a specific pallet/module.
    #[error("Module error: {0}")]
    Module(ModuleError),
    /// Some other error was emitted.
    #[error("Undecoded dispatch error: {0:?}")]
    Other(Vec<u8>),
}

impl DispatchError {
    /// Attempt to decode a runtime DispatchError, returning either the [`ModuleError`] it decodes
    /// to, along with additional details on the error, or returning the raw bytes if it could not
    /// be decoded.
    pub fn decode_from<'a>(bytes: impl Into<Cow<'a, [u8]>>, metadata: &Metadata) -> Self {
        let bytes = bytes.into();

        let dispatch_error_ty_id = match metadata.dispatch_error_ty() {
            Some(id) => id,
            None => {
                tracing::warn!(
                    "Can't decode error: sp_runtime::DispatchError was not found in Metadata"
                );
                return DispatchError::Other(bytes.into_owned())
            }
        };

        let dispatch_error_ty = match metadata.types().resolve(dispatch_error_ty_id) {
            Some(ty) => ty,
            None => {
                tracing::warn!("Can't decode error: sp_runtime::DispatchError type ID doesn't resolve to a known type");
                return DispatchError::Other(bytes.into_owned())
            }
        };

        let variant = match dispatch_error_ty.type_def() {
            TypeDef::Variant(var) => var,
            _ => {
                tracing::warn!(
                    "Can't decode error: sp_runtime::DispatchError type is not a Variant"
                );
                return DispatchError::Other(bytes.into_owned())
            }
        };

        let module_variant_idx = variant
            .variants()
            .iter()
            .find(|v| v.name() == "Module")
            .map(|v| v.index());
        let module_variant_idx = match module_variant_idx {
            Some(idx) => idx,
            None => {
                tracing::warn!("Can't decode error: sp_runtime::DispatchError does not have a 'Module' variant");
                return DispatchError::Other(bytes.into_owned())
            }
        };

        // If the error bytes don't correspond to a ModuleError, just return the bytes.
        // This is perfectly reasonable and expected, so no logging.
        if bytes[0] != module_variant_idx {
            return DispatchError::Other(bytes.into_owned())
        }

        // The remaining bytes are the module error, all being well:
        let bytes = &bytes[1..];

        // The oldest and second oldest type of error decode to this shape:
        #[derive(Decode)]
        struct LegacyModuleError {
            index: u8,
            error: u8,
        }

        // The newer case expands the error for forward compat:
        #[derive(Decode)]
        struct CurrentModuleError {
            index: u8,
            error: [u8; 4],
        }

        // try to decode into the new shape, or the old if that doesn't work
        let err = match CurrentModuleError::decode(&mut &*bytes) {
            Ok(e) => e,
            Err(_) => {
                let old_e = match LegacyModuleError::decode(&mut &*bytes) {
                    Ok(err) => err,
                    Err(_) => {
                        tracing::warn!("Can't decode error: sp_runtime::DispatchError does not match known formats");
                        return DispatchError::Other(bytes.to_vec())
                    }
                };
                CurrentModuleError {
                    index: old_e.index,
                    error: [old_e.error, 0, 0, 0],
                }
            }
        };

        let error_details = match metadata.error(err.index, err.error[0]) {
            Ok(details) => details,
            Err(_) => {
                tracing::warn!("Can't decode error: sp_runtime::DispatchError::Module details do not match known information");
                return DispatchError::Other(bytes.to_vec())
            }
        };

        DispatchError::Module(ModuleError {
            pallet: error_details.pallet().to_string(),
            error: error_details.error().to_string(),
            description: error_details.docs().to_vec(),
            error_data: ModuleErrorData {
                pallet_index: err.index,
                error: err.error,
            },
        })
    }
}

/// Block error
#[derive(Clone, Debug, Eq, thiserror::Error, PartialEq)]
pub enum BlockError {
    /// The block
    #[error(
        "Could not find a block with hash {0} (perhaps it was on a non-finalized fork?)"
    )]
    BlockHashNotFound(String),
}

impl BlockError {
    /// Produce an error that a block with the given hash cannot be found.
    pub fn block_hash_not_found(hash: impl AsRef<[u8]>) -> BlockError {
        let hash = format!("0x{}", hex::encode(hash));
        BlockError::BlockHashNotFound(hash)
    }
}

/// Transaction error.
#[derive(Clone, Debug, Eq, thiserror::Error, PartialEq)]
pub enum TransactionError {
    /// The finality subscription expired (after ~512 blocks we give up if the
    /// block hasn't yet been finalized).
    #[error("The finality subscription expired")]
    FinalitySubscriptionTimeout,
    /// The block hash that the transaction was added to could not be found.
    /// This is probably because the block was retracted before being finalized.
    #[error("The block containing the transaction can no longer be found (perhaps it was on a non-finalized fork?)")]
    BlockHashNotFound,
}

/// Details about a module error that has occurred.
#[derive(Clone, Debug, thiserror::Error)]
#[error("{pallet}: {error}\n\n{}", .description.join("\n"))]
pub struct ModuleError {
    /// The name of the pallet that the error came from.
    pub pallet: String,
    /// The name of the error.
    pub error: String,
    /// A description of the error.
    pub description: Vec<String>,
    /// A byte representation of the error.
    pub error_data: ModuleErrorData,
}

/// The error details about a module error that has occurred.
///
/// **Note**: Structure used to obtain the underlying bytes of a ModuleError.
#[derive(Clone, Debug, thiserror::Error)]
#[error("Pallet index {pallet_index}: raw error: {error:?}")]
pub struct ModuleErrorData {
    /// Index of the pallet that the error came from.
    pub pallet_index: u8,
    /// Raw error bytes.
    pub error: [u8; 4],
}

impl ModuleErrorData {
    /// Obtain the error index from the underlying byte data.
    pub fn error_index(&self) -> u8 {
        // Error index is utilized as the first byte from the error array.
        self.error[0]
    }
}

/// Something went wrong trying to encode a storage address.
#[derive(Clone, Debug, thiserror::Error)]
pub enum StorageAddressError {
    /// Storage map type must be a composite type.
    #[error("Storage map type must be a composite type")]
    MapTypeMustBeTuple,
    /// Storage lookup does not have the expected number of keys.
    #[error("Storage lookup requires {expected} keys but got {actual} keys")]
    WrongNumberOfKeys {
        /// The actual number of keys needed, based on the metadata.
        actual: usize,
        /// The number of keys provided in the storage address.
        expected: usize,
    },
    /// Storage lookup requires a type that wasn't found in the metadata.
    #[error(
        "Storage lookup requires type {0} to exist in the metadata, but it was not found"
    )]
    TypeNotFound(u32),
    /// This storage entry in the metadata does not have the correct number of hashers to fields.
    #[error(
        "Storage entry in metadata does not have the correct number of hashers to fields"
    )]
    WrongNumberOfHashers {
        /// The number of hashers in the metadata for this storage entry.
        hashers: usize,
        /// The number of fields in the metadata for this storage entry.
        fields: usize,
    },
}