use anyhow::{anyhow, Result};
use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};
use rand::prelude::*;
use std::fs::OpenOptions;
use std::io::{Cursor, Read, Seek, SeekFrom, Write};
use std::path::Path;

use thinp::file_utils;
use thinp::thin::xml::{self, Visit};

mod common;
use common::test_dir::*;
use common::thin_xml_generator::{write_xml, EmptyPoolS, FragmentedS, SingleThinS, SnapS, XmlGen};

//------------------------------------

#[derive(Debug)]
struct ThinBlock {
    thin_id: u32,
    thin_block: u64,
    data_block: u64,
    block_size: usize,
}

struct ThinReadRef {
    pub data: Vec<u8>,
}

struct ThinWriteRef<'a, W: Write + Seek> {
    file: &'a mut W,
    block_byte: u64,
    pub data: Vec<u8>,
}

impl ThinBlock {
    fn read_ref<R: Read + Seek>(&self, r: &mut R) -> Result<ThinReadRef> {
        let mut rr = ThinReadRef {
            data: vec![0; self.block_size * 512],
        };
        let byte = self.data_block * (self.block_size as u64) * 512;
        r.seek(SeekFrom::Start(byte))?;
        r.read_exact(&mut rr.data)?;
        Ok(rr)
    }

    fn zero_ref<'a, W: Write + Seek>(&self, w: &'a mut W) -> ThinWriteRef<'a, W> {
        ThinWriteRef {
            file: w,
            block_byte: self.data_block * (self.block_size as u64) * 512,
            data: vec![0; self.block_size * 512],
        }
    }

    //fn write_ref<'a, W>(&self, w: &'a mut W) -> Result<ThinWriteRef<'a, W>>
    //where
    //W: Read + Write + Seek,
    //{
    //let mut data = vec![0; self.block_size];
    //w.seek(SeekFrom::Start(self.data_block * (self.block_size as u64)))?;
    //w.read_exact(&mut data[0..])?;
    //
    //let wr = ThinWriteRef {
    //file: w,
    //block_byte: self.data_block * (self.block_size as u64),
    //data: vec![0; self.block_size],
    //};
    //
    //Ok(wr)
    //}
}

impl<'a, W: Write + Seek> Drop for ThinWriteRef<'a, W> {
    fn drop(&mut self) {
        // FIXME: We shouldn't panic in a drop function, so any IO
        // errors will have to make their way back to the user
        // another way (eg, via a flush() method).
        self.file.seek(SeekFrom::Start(self.block_byte)).unwrap();
        self.file.write_all(&self.data).unwrap();
    }
}

//------------------------------------

trait ThinVisitor {
    fn thin_block(&mut self, tb: &ThinBlock) -> Result<()>;
}

struct ThinXmlVisitor<'a, V: ThinVisitor> {
    inner: &'a mut V,
    block_size: Option<u32>,
    thin_id: Option<u32>,
}

impl<'a, V: ThinVisitor> xml::MetadataVisitor for ThinXmlVisitor<'a, V> {
    fn superblock_b(&mut self, sb: &xml::Superblock) -> Result<Visit> {
        self.block_size = Some(sb.data_block_size);
        Ok(Visit::Continue)
    }

    fn superblock_e(&mut self) -> Result<Visit> {
        Ok(Visit::Continue)
    }

    fn def_shared_b(&mut self, _name: &str) -> Result<Visit> {
        todo!();
    }

    fn def_shared_e(&mut self) -> Result<Visit> {
        todo!();
    }

    fn device_b(&mut self, d: &xml::Device) -> Result<Visit> {
        self.thin_id = Some(d.dev_id);
        Ok(Visit::Continue)
    }

    fn device_e(&mut self) -> Result<Visit> {
        Ok(Visit::Continue)
    }

    fn map(&mut self, m: &xml::Map) -> Result<Visit> {
        for i in 0..m.len {
            let block = ThinBlock {
                thin_id: self.thin_id.unwrap(),
                thin_block: m.thin_begin + i,
                data_block: m.data_begin + i,
                block_size: self.block_size.unwrap() as usize,
            };
            self.inner.thin_block(&block)?;
        }
        Ok(Visit::Continue)
    }

    fn ref_shared(&mut self, _name: &str) -> Result<Visit> {
        todo!();
    }

    fn eof(&mut self) -> Result<Visit> {
        Ok(Visit::Stop)
    }
}

fn thin_visit<R, M>(input: R, visitor: &mut M) -> Result<()>
where
    R: Read,
    M: ThinVisitor,
{
    let mut xml_visitor = ThinXmlVisitor {
        inner: visitor,
        block_size: None,
        thin_id: None,
    };

    xml::read(input, &mut xml_visitor)
}

//------------------------------------

// To test thin_shrink we'd like to stamp a known pattern across the
// provisioned areas of the thins in the pool, do the shrink, verify
// the patterns.

// A simple linear congruence generator used to create the data to
// go into the thin blocks.
struct Generator {
    x: u64,
    a: u64,
    c: u64,
}

impl Generator {
    fn new() -> Generator {
        Generator {
            x: 0,
            a: 6364136223846793005,
            c: 1442695040888963407,
        }
    }

    fn step(&mut self) {
        self.x = self.a.wrapping_mul(self.x).wrapping_add(self.c)
    }

    fn fill_buffer(&mut self, seed: u64, bytes: &mut [u8]) -> Result<()> {
        self.x = seed;

        assert!(bytes.len() % 8 == 0);
        let nr_words = bytes.len() / 8;
        let mut out = Cursor::new(bytes);

        for _ in 0..nr_words {
            out.write_u64::<LittleEndian>(self.x)?;
            self.step();
        }

        Ok(())
    }

    fn verify_buffer(&mut self, seed: u64, bytes: &[u8]) -> Result<bool> {
        self.x = seed;

        assert!(bytes.len() % 8 == 0);
        let nr_words = bytes.len() / 8;
        let mut input = Cursor::new(bytes);

        for _ in 0..nr_words {
            let w = input.read_u64::<LittleEndian>()?;
            if w != self.x {
                eprintln!("{} != {}", w, self.x);
                return Ok(false);
            }
            self.step();
        }

        Ok(true)
    }
}

//------------------------------------

struct Stamper<'a, W: Write + Seek> {
    data_file: &'a mut W,
    seed: u64,
}

impl<'a, W: Write + Seek> Stamper<'a, W> {
    fn new(w: &'a mut W, seed: u64) -> Stamper<'a, W> {
        Stamper { data_file: w, seed }
    }
}

impl<'a, W: Write + Seek> ThinVisitor for Stamper<'a, W> {
    fn thin_block(&mut self, b: &ThinBlock) -> Result<()> {
        let mut wr = b.zero_ref(self.data_file);
        let mut gen = Generator::new();
        gen.fill_buffer(self.seed ^ (b.thin_id as u64) ^ b.thin_block, &mut wr.data)?;
        Ok(())
    }
}

//------------------------------------

struct Verifier<'a, R: Read + Seek> {
    data_file: &'a mut R,
    seed: u64,
}

impl<'a, R: Read + Seek> Verifier<'a, R> {
    fn new(r: &'a mut R, seed: u64) -> Verifier<'a, R> {
        Verifier { data_file: r, seed }
    }
}

impl<'a, R: Read + Seek> ThinVisitor for Verifier<'a, R> {
    fn thin_block(&mut self, b: &ThinBlock) -> Result<()> {
        let rr = b.read_ref(self.data_file)?;
        let mut gen = Generator::new();
        if !gen.verify_buffer(self.seed ^ (b.thin_id as u64) ^ b.thin_block, &rr.data)? {
            return Err(anyhow!("data verify failed for {:?}", b));
        }
        Ok(())
    }
}

//------------------------------------

fn create_data_file(data_path: &Path, xml_path: &Path) -> Result<()> {
    let input = OpenOptions::new().read(true).write(false).open(xml_path)?;

    let sb = xml::read_superblock(input)?;
    let nr_blocks = sb.nr_data_blocks as u64;
    let block_size = sb.data_block_size as u64 * 512;

    let _file = file_utils::create_sized_file(data_path, nr_blocks * block_size)?;
    Ok(())
}

fn stamp(xml_path: &Path, data_path: &Path, seed: u64) -> Result<()> {
    let mut data = OpenOptions::new()
        .read(false)
        .write(true)
        .open(&data_path)?;
    let xml = OpenOptions::new().read(true).write(false).open(&xml_path)?;

    let mut stamper = Stamper::new(&mut data, seed);
    thin_visit(xml, &mut stamper)
}

fn verify(xml_path: &Path, data_path: &Path, seed: u64) -> Result<()> {
    let mut data = OpenOptions::new()
        .read(true)
        .write(false)
        .open(&data_path)?;
    let xml = OpenOptions::new().read(true).write(false).open(&xml_path)?;

    let mut verifier = Verifier::new(&mut data, seed);
    thin_visit(xml, &mut verifier)
}

trait Scenario {
    fn get_new_nr_blocks(&self) -> u64;
}

fn test_shrink<S>(scenario: &mut S) -> Result<()>
where
    S: Scenario + XmlGen,
{
    let mut td = TestDir::new()?;
    let xml_before = td.mk_path("before.xml");
    let xml_after = td.mk_path("after.xml");
    let data_path = td.mk_path("metadata.bin");

    write_xml(&xml_before, scenario)?;
    create_data_file(&data_path, &xml_before)?;

    let mut rng = rand::thread_rng();
    let seed = rng.gen::<u64>();

    stamp(&xml_before, &data_path, seed)?;
    verify(&xml_before, &data_path, seed)?;

    let new_nr_blocks = scenario.get_new_nr_blocks();
    thinp::shrink::toplevel::shrink(&xml_before, &xml_after, &data_path, new_nr_blocks, true)?;

    verify(&xml_after, &data_path, seed)?;
    Ok(())
}

//------------------------------------

impl Scenario for EmptyPoolS {
    fn get_new_nr_blocks(&self) -> u64 {
        512
    }
}

#[test]
fn shrink_empty_pool() -> Result<()> {
    let mut s = EmptyPoolS {};
    test_shrink(&mut s)
}

//------------------------------------

impl Scenario for SingleThinS {
    fn get_new_nr_blocks(&self) -> u64 {
        self.new_nr_data_blocks
    }
}

#[test]
fn shrink_single_no_move_1() -> Result<()> {
    let mut s = SingleThinS::new(0, 1024, 2048, 1280);
    test_shrink(&mut s)
}

#[test]
fn shrink_single_no_move_2() -> Result<()> {
    let mut s = SingleThinS::new(100, 1024, 2048, 1280);
    test_shrink(&mut s)
}

#[test]
fn shrink_single_no_move_3() -> Result<()> {
    let mut s = SingleThinS::new(1024, 1024, 2048, 2048);
    test_shrink(&mut s)
}

#[test]
fn shrink_single_partial_move() -> Result<()> {
    let mut s = SingleThinS::new(1024, 1024, 2048, 1280);
    test_shrink(&mut s)
}

#[test]
fn shrink_single_total_move() -> Result<()> {
    let mut s = SingleThinS::new(2048, 1024, 1024 + 2048, 1280);
    test_shrink(&mut s)
}

#[test]
fn shrink_insufficient_space() -> Result<()> {
    let mut s = SingleThinS::new(0, 2048, 3000, 1280);
    match test_shrink(&mut s) {
        Ok(_) => Err(anyhow!("Shrink unexpectedly succeeded")),
        Err(_) => Ok(()),
    }
}

//------------------------------------

impl Scenario for FragmentedS {
    fn get_new_nr_blocks(&self) -> u64 {
        self.new_nr_data_blocks
    }
}

#[test]
fn shrink_fragmented_thin_1() -> Result<()> {
    let mut s = FragmentedS::new(1, 2048);
    test_shrink(&mut s)
}

#[test]
fn shrink_fragmented_thin_2() -> Result<()> {
    let mut s = FragmentedS::new(2, 2048);
    test_shrink(&mut s)
}

#[test]
fn shrink_fragmented_thin_8() -> Result<()> {
    let mut s = FragmentedS::new(2, 2048);
    test_shrink(&mut s)
}

#[test]
fn shrink_fragmented_thin_64() -> Result<()> {
    let mut s = FragmentedS::new(2, 2048);
    test_shrink(&mut s)
}

//------------------------------------

impl Scenario for SnapS {
    fn get_new_nr_blocks(&self) -> u64 {
        self.new_nr_data_blocks
    }
}

#[test]
fn shrink_identical_snap() -> Result<()> {
    let mut s = SnapS::new(1024, 1, 0);
    test_shrink(&mut s)
}

//------------------------------------