// Copyright 2015, 2016, 2017 Parity Technologies (UK) Ltd.
// This file is part of Parity.

// Parity is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Parity is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Parity.  If not, see <http://www.gnu.org/licenses/>.

use std::io::{Read, Write};
use serde::{Deserialize, Deserializer, Error};
use serde::de::{Visitor, MapVisitor};
use serde_json;
use super::Crypto;

/// Vault meta file
#[derive(Debug, PartialEq, Serialize)]
pub struct VaultFile {
	/// Vault password, encrypted with vault password
	pub crypto: Crypto,
	/// Vault metadata string
	pub meta: Option<String>,
}

enum VaultFileField {
	Crypto,
	Meta,
}

impl Deserialize for VaultFileField {
	fn deserialize<D>(deserializer: &mut D) -> Result<VaultFileField, D::Error>
		where D: Deserializer
	{
		deserializer.deserialize(VaultFileFieldVisitor)
	}
}

struct VaultFileFieldVisitor;

impl Visitor for VaultFileFieldVisitor {
	type Value = VaultFileField;

	fn visit_str<E>(&mut self, value: &str) -> Result<Self::Value, E>
		where E: Error
	{
		match value {
			"crypto" => Ok(VaultFileField::Crypto),
			"meta" => Ok(VaultFileField::Meta),
			_ => Err(Error::custom(format!("Unknown field: '{}'", value))),
		}
	}
}

impl Deserialize for VaultFile {
	fn deserialize<D>(deserializer: &mut D) -> Result<VaultFile, D::Error>
		where D: Deserializer
	{
		static FIELDS: &'static [&'static str] = &["crypto", "meta"];
		deserializer.deserialize_struct("VaultFile", FIELDS, VaultFileVisitor)
	}
}

struct VaultFileVisitor;

impl Visitor for VaultFileVisitor {
	type Value = VaultFile;

	fn visit_map<V>(&mut self, mut visitor: V) -> Result<Self::Value, V::Error>
		where V: MapVisitor
	{
		let mut crypto = None;
		let mut meta = None;

		loop {
			match visitor.visit_key()? {
				Some(VaultFileField::Crypto) => { crypto = Some(visitor.visit_value()?); },
				Some(VaultFileField::Meta) => { meta = Some(visitor.visit_value()?); }
				None => { break; },
			}
		}

		let crypto = match crypto {
			Some(crypto) => crypto,
			None => visitor.missing_field("crypto")?,
		};

		visitor.end()?;

		let result = VaultFile {
			crypto: crypto,
			meta: meta,
		};

		Ok(result)
	}
}

impl VaultFile {
	pub fn load<R>(reader: R) -> Result<Self, serde_json::Error> where R: Read {
		serde_json::from_reader(reader)
	}

	pub fn write<W>(&self, writer: &mut W) -> Result<(), serde_json::Error> where W: Write {
		serde_json::to_writer(writer, self)
	}
}

#[cfg(test)]
mod test {
	use serde_json;
	use json::{VaultFile, Crypto, Cipher, Aes128Ctr, Kdf, Pbkdf2, Prf};

	#[test]
	fn to_and_from_json() {
		let file = VaultFile {
			crypto: Crypto {
				cipher: Cipher::Aes128Ctr(Aes128Ctr {
					iv: "0155e3690be19fbfbecabcd440aa284b".into(),
				}),
				ciphertext: "4d6938a1f49b7782".into(),
				kdf: Kdf::Pbkdf2(Pbkdf2 {
					c: 1024,
					dklen: 32,
					prf: Prf::HmacSha256,
					salt: "b6a9338a7ccd39288a86dba73bfecd9101b4f3db9c9830e7c76afdbd4f6872e5".into(),
				}),
				mac: "16381463ea11c6eb2239a9f339c2e780516d29d234ce30ac5f166f9080b5a262".into(),
			},
			meta: Some("{}".into()),
		};

		let serialized = serde_json::to_string(&file).unwrap();
		let deserialized = serde_json::from_str(&serialized).unwrap();

		assert_eq!(file, deserialized);
	}
}