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/*
 * Copyright 2022 Fluence Labs Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#![forbid(unsafe_code)]
#![warn(rust_2018_idioms)]
#![deny(
    dead_code,
    nonstandard_style,
    unused_imports,
    unused_mut,
    unused_variables,
    unused_unsafe,
    unreachable_patterns
)]

use serde::Deserialize;
use serde::Serialize;

use std::fmt;
use std::marker::PhantomData;

#[derive(Clone, Serialize, Deserialize)]
#[serde(transparent)]
pub struct CID<T: ?Sized>(String, #[serde(skip)] PhantomData<*const T>);

impl<T: ?Sized> CID<T> {
    pub fn new(cid: impl Into<String>) -> Self {
        Self(cid.into(), PhantomData)
    }

    pub fn into_inner(self) -> String {
        self.0
    }
}

impl<T: ?Sized> fmt::Debug for CID<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_tuple("CID").field(&self.0).finish()
    }
}

impl<Val> PartialEq for CID<Val> {
    fn eq(&self, other: &Self) -> bool {
        self.0 == other.0
    }
}

impl<Val> Eq for CID<Val> {}

impl<Val> std::hash::Hash for CID<Val> {
    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
        self.0.hash(state);
        self.1.hash(state);
    }
}

impl<T: ?Sized> From<CID<T>> for String {
    fn from(value: CID<T>) -> Self {
        value.0
    }
}

// TODO we might refactor this to `SerializationFormat` trait
// that both transform data to binary/text form (be it JSON, CBOR or something else)
// and produces CID too
pub fn json_data_cid<Val: ?Sized>(data: &[u8]) -> CID<Val> {
    use cid::Cid;
    use multihash::{Code, MultihashDigest};

    // the Sha2_256 is current IPFS default hash
    let digest = Code::Sha2_256.digest(data);
    // seems to be better than RAW_CODEC = 0x55
    const JSON_CODEC: u64 = 0x0200;

    let cid = Cid::new_v1(JSON_CODEC, digest);
    CID::new(cid.to_string())
}

pub struct CidCalculationError(serde_json::Error);

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

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

impl From<serde_json::Error> for CidCalculationError {
    fn from(source: serde_json::Error) -> Self {
        Self(source)
    }
}

impl std::error::Error for CidCalculationError {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        Some(&self.0)
    }
}

/// Calculate a CID of JSON-serialized value.
pub fn value_to_json_cid<Val: Serialize>(value: &Val) -> Result<CID<Val>, CidCalculationError> {
    let data = serde_json::to_vec(value)?;
    Ok(json_data_cid(&data))
}