use std::convert::Infallible;
use std::error::Error as StdError;
use std::{fmt, io, str};

use heed::{MdbError, Error as HeedError};
use rayon::ThreadPoolBuildError;
use serde_json::{Map, Value};

use crate::search::ParserRule;
use crate::{DocumentId, FieldId};

pub type Object = Map<String, Value>;

#[derive(Debug)]
pub enum Error {
    InternalError(InternalError),
    IoError(io::Error),
    UserError(UserError),
}

#[derive(Debug)]
pub enum InternalError {
    DatabaseClosing,
    DatabaseMissingEntry { db_name: &'static str, key: Option<&'static str> },
    FieldIdMapMissingEntry(FieldIdMapMissingEntry),
    Fst(fst::Error),
    GrenadInvalidCompressionType,
    IndexingMergingKeys { process: &'static str },
    InvalidDatabaseTyping,
    RayonThreadPool(ThreadPoolBuildError),
    SerdeJson(serde_json::Error),
    Serialization(SerializationError),
    Store(MdbError),
    Utf8(str::Utf8Error),
}

#[derive(Debug)]
pub enum SerializationError {
    Decoding { db_name: Option<&'static str> },
    Encoding { db_name: Option<&'static str> },
    InvalidNumberSerialization,
}

#[derive(Debug)]
pub enum FieldIdMapMissingEntry {
    FieldId { field_id: FieldId, process: &'static str },
    FieldName { field_name: String, process: &'static str },
}

#[derive(Debug)]
pub enum UserError {
    AttributeLimitReached,
    Csv(csv::Error),
    MaxDatabaseSizeReached,
    DocumentLimitReached,
    FilterParsing(pest::error::Error<ParserRule>),
    InvalidCriterionName { name: String },
    InvalidDocumentId { document_id: Value },
    InvalidFilterAttribute(pest::error::Error<ParserRule>),
    InvalidStoreFile,
    MissingDocumentId { document: Object },
    MissingPrimaryKey,
    NoSpaceLeftOnDevice,
    PrimaryKeyCannotBeChanged,
    PrimaryKeyCannotBeReset,
    SerdeJson(serde_json::Error),
    UnknownInternalDocumentId { document_id: DocumentId },
}

impl From<io::Error> for Error {
    fn from(error: io::Error) -> Error {
        // TODO must be improved and more precise
        Error::IoError(error)
    }
}

impl From<fst::Error> for Error {
    fn from(error: fst::Error) -> Error {
        Error::InternalError(InternalError::Fst(error))
    }
}

impl<E> From<grenad::Error<E>> for Error where Error: From<E> {
    fn from(error: grenad::Error<E>) -> Error {
        match error {
            grenad::Error::Io(error) => Error::IoError(error),
            grenad::Error::Merge(error) => Error::from(error),
            grenad::Error::InvalidCompressionType => {
                Error::InternalError(InternalError::GrenadInvalidCompressionType)
            },
        }
    }
}

impl From<str::Utf8Error> for Error {
    fn from(error: str::Utf8Error) -> Error {
        Error::InternalError(InternalError::Utf8(error))
    }
}

impl From<Infallible> for Error {
    fn from(_error: Infallible) -> Error {
        unreachable!()
    }
}

impl From<HeedError> for Error {
    fn from(error: HeedError) -> Error {
        use self::Error::*;
        use self::InternalError::*;
        use self::SerializationError::*;
        use self::UserError::*;

        match error {
            HeedError::Io(error) => Error::from(error),
            HeedError::Mdb(MdbError::MapFull) => UserError(MaxDatabaseSizeReached),
            HeedError::Mdb(MdbError::Invalid) => UserError(InvalidStoreFile),
            HeedError::Mdb(error) => InternalError(Store(error)),
            HeedError::Encoding => InternalError(Serialization(Encoding { db_name: None })),
            HeedError::Decoding => InternalError(Serialization(Decoding { db_name: None })),
            HeedError::InvalidDatabaseTyping => InternalError(InvalidDatabaseTyping),
            HeedError::DatabaseClosing => InternalError(DatabaseClosing),
        }
    }
}

impl From<ThreadPoolBuildError> for Error {
    fn from(error: ThreadPoolBuildError) -> Error {
        Error::InternalError(InternalError::RayonThreadPool(error))
    }
}

impl From<FieldIdMapMissingEntry> for Error {
    fn from(error: FieldIdMapMissingEntry) -> Error {
        Error::InternalError(InternalError::FieldIdMapMissingEntry(error))
    }
}

impl From<InternalError> for Error {
    fn from(error: InternalError) -> Error {
        Error::InternalError(error)
    }
}

impl From<UserError> for Error {
    fn from(error: UserError) -> Error {
        Error::UserError(error)
    }
}

impl From<SerializationError> for Error {
    fn from(error: SerializationError) -> Error {
        Error::InternalError(InternalError::Serialization(error))
    }
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Self::InternalError(error) => write!(f, "internal: {}", error),
            Self::IoError(error) => error.fmt(f),
            Self::UserError(error) => error.fmt(f),
        }
    }
}

impl StdError for Error {}

impl fmt::Display for InternalError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Self::DatabaseMissingEntry { db_name, key } => {
                write!(f, "missing {} in the {} database", key.unwrap_or("key"), db_name)
            },
            Self::FieldIdMapMissingEntry(error) => error.fmt(f),
            Self::Fst(error) => error.fmt(f),
            Self::GrenadInvalidCompressionType => {
                f.write_str("invalid compression type have been specified to grenad")
            },
            Self::IndexingMergingKeys { process } => {
                write!(f, "invalid merge while processing {}", process)
            },
            Self::Serialization(error) => error.fmt(f),
            Self::InvalidDatabaseTyping => HeedError::InvalidDatabaseTyping.fmt(f),
            Self::RayonThreadPool(error) => error.fmt(f),
            Self::SerdeJson(error) => error.fmt(f),
            Self::DatabaseClosing => HeedError::DatabaseClosing.fmt(f),
            Self::Store(error) => error.fmt(f),
            Self::Utf8(error) => error.fmt(f),
        }
    }
}

impl StdError for InternalError {}

impl fmt::Display for UserError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Self::AttributeLimitReached => f.write_str("maximum number of attributes reached"),
            Self::Csv(error) => error.fmt(f),
            Self::DocumentLimitReached => f.write_str("maximum number of documents reached"),
            Self::FilterParsing(error) => error.fmt(f),
            Self::InvalidCriterionName { name } => write!(f, "invalid criterion {}", name),
            Self::InvalidDocumentId { document_id } => {
                let json = serde_json::to_string(document_id).unwrap();
                write!(f, "document identifier is invalid {}", json)
            },
            Self::InvalidFilterAttribute(error) => error.fmt(f),
            Self::MissingDocumentId { document } => {
                let json = serde_json::to_string(document).unwrap();
                write!(f, "document doesn't have an identifier {}", json)
            },
            Self::MissingPrimaryKey => f.write_str("missing primary key"),
            Self::MaxDatabaseSizeReached => f.write_str("maximum database size reached"),
            // TODO where can we find it instead of writing the text ourselves?
            Self::NoSpaceLeftOnDevice => f.write_str("no space left on device"),
            Self::InvalidStoreFile => f.write_str("store file is not a valid database file"),
            Self::PrimaryKeyCannotBeChanged => {
                f.write_str("primary key cannot be changed if the database contains documents")
            },
            Self::PrimaryKeyCannotBeReset => {
                f.write_str("primary key cannot be reset if the database contains documents")
            },
            Self::SerdeJson(error) => error.fmt(f),
            Self::UnknownInternalDocumentId { document_id } => {
                write!(f, "an unknown internal document id have been used ({})", document_id)
            },
        }
    }
}

impl StdError for UserError {}

impl fmt::Display for FieldIdMapMissingEntry {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Self::FieldId { field_id, process } => {
                write!(f, "unknown field id {} coming from the {} process", field_id, process)
            },
            Self::FieldName { field_name, process } => {
                write!(f, "unknown field name {} coming from the {} process", field_name, process)
            },
        }
    }
}

impl StdError for FieldIdMapMissingEntry {}

impl fmt::Display for SerializationError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Self::Decoding { db_name: Some(name) } => {
                write!(f, "decoding from the {} database failed", name)
            },
            Self::Decoding { db_name: None } => f.write_str("decoding failed"),
            Self::Encoding { db_name: Some(name) } => {
                write!(f, "encoding into the {} database failed", name)
            },
            Self::Encoding { db_name: None } => f.write_str("encoding failed"),
            Self::InvalidNumberSerialization => f.write_str("number is not a valid finite number"),
        }
    }
}

impl StdError for SerializationError {}