// Copyright 2019-2020 Georges Racinet <georges.racinet@octobus.net>

//

// This software may be used and distributed according to the terms of the

// GNU General Public License version 2 or any later version.

use clap::*;

use hg::revlog::node::*;

use hg::revlog::nodemap::*;

use hg::revlog::*;

use memmap::MmapOptions;

use rand::Rng;

use std::fs::File;

use std::io;

use std::io::Write;

use std::path::{Path, PathBuf};

use std::str::FromStr;

use std::time::Instant;

mod index;

use index::Index;

fn mmap_index(repo_path: &Path) -> Index {

    let mut path = PathBuf::from(repo_path);

    path.extend([".hg", "store", "00changelog.i"].iter());

    Index::load_mmap(path)

}

fn mmap_nodemap(path: &Path) -> NodeTree {

    let file = File::open(path).unwrap();

    let mmap = unsafe { MmapOptions::new().map(&file).unwrap() };

    let len = mmap.len();

    NodeTree::load_bytes(Box::new(mmap), len)

}

/// Scan the whole index and create the corresponding nodemap file at `path`

fn create(index: &Index, path: &Path) -> io::Result<()> {

    let mut file = File::create(path)?;

    let start = Instant::now();

    let mut nm = NodeTree::default();

    for rev in 0..index.len() {

        let rev = rev as Revision;

        nm.insert(index, index.node(rev).unwrap(), rev).unwrap();

    }

    eprintln!("Nodemap constructed in RAM in {:?}", start.elapsed());

    file.write(&nm.into_readonly_and_added_bytes().1)?;

    eprintln!("Nodemap written to disk");

    Ok(())

}

fn query(index: &Index, nm: &NodeTree, prefix: &str) {

    let start = Instant::now();

    let res = nm.find_hex(index, prefix);

    println!("Result found in {:?}: {:?}", start.elapsed(), res);

}

fn bench(index: &Index, nm: &NodeTree, queries: usize) {

    let len = index.len() as u32;

    let mut rng = rand::thread_rng();

    let nodes: Vec<Node> = (0..queries)

        .map(|_| {

            index

                .node((rng.gen::<u32>() % len) as Revision)

                .unwrap()

                .clone()

        })

        .collect();

    if queries < 10 {

        let nodes_hex: Vec<String> =

            nodes.iter().map(|n| n.encode_hex()).collect();

        println!("Nodes: {:?}", nodes_hex);

    }

    let mut last: Option<Revision> = None;

    let start = Instant::now();

    for node in nodes.iter() {

        last = nm.find_bin(index, node.into()).unwrap();

    }

    let elapsed = start.elapsed();

    println!(

        "Did {} queries in {:?} (mean {:?}), last was {:?} with result {:?}",

        queries,

        elapsed,

        elapsed / (queries as u32),

        nodes.last().unwrap().encode_hex(),

        last

    );

}

fn main() {

    let matches = App::new("Nodemap pure Rust example")

        .arg(

            Arg::with_name("REPOSITORY")

                .help("Path to the repository, always necessary for its index")

                .required(true),

        )

        .arg(

            Arg::with_name("NODEMAP_FILE")

                .help("Path to the nodemap file, independent of REPOSITORY")

                .required(true),

        )

        .subcommand(

            SubCommand::with_name("create")

                .about("Create NODEMAP_FILE by scanning repository index"),

        )

        .subcommand(

            SubCommand::with_name("query")

                .about("Query NODEMAP_FILE for PREFIX")

                .arg(Arg::with_name("PREFIX").required(true)),

        )

        .subcommand(

            SubCommand::with_name("bench")

                .about(

                    "Perform #QUERIES random successful queries on NODEMAP_FILE")

                .arg(Arg::with_name("QUERIES").required(true)),

        )

        .get_matches();

    let repo = matches.value_of("REPOSITORY").unwrap();

    let nm_path = matches.value_of("NODEMAP_FILE").unwrap();

    let index = mmap_index(&Path::new(repo));

    if let Some(_) = matches.subcommand_matches("create") {

        println!("Creating nodemap file {} for repository {}", nm_path, repo);

        create(&index, &Path::new(nm_path)).unwrap();

        return;

    }

    let nm = mmap_nodemap(&Path::new(nm_path));

    if let Some(matches) = matches.subcommand_matches("query") {

        let prefix = matches.value_of("PREFIX").unwrap();

        println!(

            "Querying {} in nodemap file {} of repository {}",

            prefix, nm_path, repo

        );

        query(&index, &nm, prefix);

    }

    if let Some(matches) = matches.subcommand_matches("bench") {

        let queries =

            usize::from_str(matches.value_of("QUERIES").unwrap()).unwrap();

        println!(

            "Doing {} random queries in nodemap file {} of repository {}",

            queries, nm_path, repo

        );

        bench(&index, &nm, queries);

    }

}