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// MIT License
//
// Copyright (c) 2022-2024 Robin Doer
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to
// deal in the Software without restriction, including without limitation the
// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
// sell copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
// IN THE SOFTWARE.

#[cfg(test)]
mod tests;

use nuts_backend::{Binary, Create, Open, ReceiveHeader, HEADER_MAX_SIZE};
use std::convert::TryInto;
use std::mem;
use std::path::Path;

use crate::error::{Error, Result};
use crate::id::Id;
use crate::{read_header, write_header, DirectoryBackend};

const BLOCK_MIN_SIZE: u32 = 512;

/// [Options](nuts_backend::Create) needed to create the backend.
///
/// You must pass the path, where the directory tree should be stored, to
/// [`CreateOptions::for_path()`], if creating a `CreateOptions` instance.
///
/// Furthermore the following options can be specified:
///
/// * [`CreateOptions::with_bsize()`]: Specifies the block size of the backend.
///   This is the number of bytes, which can  be stored in an individual block.
///   The minimum block size is 512 bytes. The default is `512`.
#[derive(Clone, Debug)]
pub struct CreateOptions<P: AsRef<Path>> {
    path: P,
    bsize: u32,
}

impl<P: AsRef<Path>> CreateOptions<P> {
    /// Creates a new `CreateOptions` instance.
    ///
    /// You must pass the `path`, where the directory tree should be stored, to
    /// the function.
    ///
    /// For further options default values are applied.
    pub fn for_path(path: P) -> Self {
        CreateOptions {
            path,
            bsize: BLOCK_MIN_SIZE,
        }
    }

    /// Assigns a new block size to the options.
    ///
    /// This is the number of bytes, which can  be stored in an individual
    /// block.
    pub fn with_bsize(mut self, bsize: u32) -> Self {
        self.bsize = bsize;
        self
    }

    fn validate(&self) -> Result<()> {
        if self.bsize >= BLOCK_MIN_SIZE {
            Ok(())
        } else {
            Err(Error::InvalidBlockSize(self.bsize))
        }
    }
}

impl<P: AsRef<Path>> Create<DirectoryBackend<P>> for CreateOptions<P> {
    fn settings(&self) -> Settings {
        Settings { bsize: self.bsize }
    }

    fn build(self, header: [u8; HEADER_MAX_SIZE], overwrite: bool) -> Result<DirectoryBackend<P>> {
        self.validate()?;

        if !overwrite {
            let header_path = Id::min().to_pathbuf(self.path.as_ref());

            if header_path.exists() {
                return Err(Error::Exists);
            }
        }

        write_header(self.path.as_ref(), self.bsize, &header)?;

        Ok(DirectoryBackend {
            bsize: self.bsize,
            path: self.path,
        })
    }
}

/// [Options](nuts_backend::Open) needed to open the backend.
///
/// You must pass the path, where the directory tree is stored, to
/// [`OpenOptions::for_path()`], if creating a `OpenOptions` instance.
pub struct OpenOptions<P: AsRef<Path>> {
    path: P,
}

impl<P: AsRef<Path>> OpenOptions<P> {
    /// Creates a new `OpenOptions` instance.
    ///
    /// You must pass the `path`, where the directory tree should is stored, to
    /// the function.
    pub fn for_path(path: P) -> OpenOptions<P> {
        OpenOptions { path }
    }
}

impl<P: AsRef<Path>> ReceiveHeader<DirectoryBackend<P>> for OpenOptions<P> {
    fn get_header_bytes(&mut self, bytes: &mut [u8; HEADER_MAX_SIZE]) -> Result<()> {
        read_header(self.path.as_ref(), bytes)
    }
}

impl<P: AsRef<Path>> Open<DirectoryBackend<P>> for OpenOptions<P> {
    fn build(self, settings: Settings) -> Result<DirectoryBackend<P>> {
        Ok(DirectoryBackend {
            bsize: settings.bsize,
            path: self.path,
        })
    }
}

/// [Settings](nuts_backend::Backend::Settings) used by the backend.
#[derive(Clone, Debug)]
pub struct Settings {
    bsize: u32,
}

impl Binary for Settings {
    fn from_bytes(bytes: &[u8]) -> Option<Settings> {
        if bytes.len() == mem::size_of::<u32>() {
            let bytes = bytes.try_into().unwrap();
            let bsize = u32::from_be_bytes(bytes);

            Some(Settings { bsize })
        } else {
            None
        }
    }

    fn as_bytes(&self) -> Vec<u8> {
        self.bsize.to_be_bytes().to_vec()
    }
}