// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

/*!
 * rusti - A REPL using the JIT backend
 *
 * Rusti works by serializing state between lines of input. This means that each
 * line can be run in a separate task, and the only limiting factor is that all
 * local bound variables are encodable.
 *
 * This is accomplished by feeding in generated input to rustc for execution in
 * the JIT compiler. Currently input actually gets fed in three times to get
 * information about the program.
 *
 * - Pass #1
 *   In this pass, the input is simply thrown at the parser and the input comes
 *   back. This validates the structure of the program, and at this stage the
 *   global items (fns, structs, impls, traits, etc.) are filtered from the
 *   input into the "global namespace". These declarations shadow all previous
 *   declarations of an item by the same name.
 *
 * - Pass #2
 *   After items have been stripped, the remaining input is passed to rustc
 *   along with all local variables declared (initialized to nothing). This pass
 *   runs up to typechecking. From this, we can learn about the types of each
 *   bound variable, what variables are bound, and also ensure that all the
 *   types are encodable (the input can actually be run).
 *
 * - Pass #3
 *   Finally, a program is generated to deserialize the local variable state,
 *   run the code input, and then reserialize all bindings back into a local
 *   hash map. Once this code runs, the input has fully been run and the REPL
 *   waits for new input.
 *
 * Encoding/decoding is done with EBML, and there is simply a map of ~str ->
 * ~[u8] maintaining the values of each local binding (by name).
 */

#[link(name = "rusti",
       vers = "0.7-pre",
       uuid = "7fb5bf52-7d45-4fee-8325-5ad3311149fc",
       url = "https://github.com/mozilla/rust/tree/master/src/rusti")];

#[license = "MIT/ASL2"];
#[crate_type = "lib"];

extern mod extra;
extern mod rustc;
extern mod syntax;

use std::{libc, io, os, task, vec};
use std::cell::Cell;
use extra::rl;

use rustc::driver::{driver, session};
use syntax::{ast, diagnostic};
use syntax::ast_util::*;
use syntax::parse::token;
use syntax::print::pprust;

use program::Program;
use utils::*;

mod program;
pub mod utils;

/**
 * A structure shared across REPL instances for storing history
 * such as statements and view items. I wish the AST was sendable.
 */
pub struct Repl {
    prompt: ~str,
    binary: ~str,
    running: bool,
    lib_search_paths: ~[~str],

    program: Program,
}

// Action to do after reading a :command
enum CmdAction {
    action_none,
    action_run_line(~str),
}

/// Run an input string in a Repl, returning the new Repl.
fn run(mut repl: Repl, input: ~str) -> Repl {
    // Build some necessary rustc boilerplate for compiling things
    let binary = repl.binary.to_managed();
    let options = @session::options {
        crate_type: session::unknown_crate,
        binary: binary,
        addl_lib_search_paths: @mut repl.lib_search_paths.map(|p| Path(*p)),
        jit: true,
        .. copy *session::basic_options()
    };
    // Because we assume that everything is encodable (and assert so), add some
    // extra helpful information if the error crops up. Otherwise people are
    // bound to be very confused when they find out code is running that they
    // never typed in...
    let sess = driver::build_session(options, |cm, msg, lvl| {
        diagnostic::emit(cm, msg, lvl);
        if msg.contains("failed to find an implementation of trait") &&
           msg.contains("extra::serialize::Encodable") {
            diagnostic::emit(cm,
                             "Currrently rusti serializes bound locals between \
                              different lines of input. This means that all \
                              values of local variables need to be encodable, \
                              and this type isn't encodable",
                             diagnostic::note);
        }
    });
    let intr = token::get_ident_interner();

    //
    // Stage 1: parse the input and filter it into the program (as necessary)
    //
    debug!("parsing: %s", input);
    let crate = parse_input(sess, binary, input);
    let mut to_run = ~[];       // statements to run (emitted back into code)
    let new_locals = @mut ~[];  // new locals being defined
    let mut result = None;      // resultant expression (to print via pp)
    do find_main(crate, sess) |blk| {
        // Fish out all the view items, be sure to record 'extern mod' items
        // differently beause they must appear before all 'use' statements
        for blk.node.view_items.each |vi| {
            let s = do with_pp(intr) |pp, _| {
                pprust::print_view_item(pp, *vi);
            };
            match vi.node {
                ast::view_item_extern_mod(*) => {
                    repl.program.record_extern(s);
                }
                ast::view_item_use(*) => { repl.program.record_view_item(s); }
            }
        }

        // Iterate through all of the block's statements, inserting them into
        // the correct portions of the program
        for blk.node.stmts.each |stmt| {
            let s = do with_pp(intr) |pp, _| { pprust::print_stmt(pp, *stmt); };
            match stmt.node {
                ast::stmt_decl(d, _) => {
                    match d.node {
                        ast::decl_item(it) => {
                            let name = sess.str_of(it.ident);
                            match it.node {
                                // Structs are treated specially because to make
                                // them at all usable they need to be decorated
                                // with #[deriving(Encoable, Decodable)]
                                ast::item_struct(*) => {
                                    repl.program.record_struct(name, s);
                                }
                                // Item declarations are hoisted out of main()
                                _ => { repl.program.record_item(name, s); }
                            }
                        }

                        // Local declarations must be specially dealt with,
                        // record all local declarations for use later on
                        ast::decl_local(l) => {
                            let mutbl = l.node.is_mutbl;
                            do each_binding(l) |path, _| {
                                let s = do with_pp(intr) |pp, _| {
                                    pprust::print_path(pp, path, false);
                                };
                                new_locals.push((s, mutbl));
                            }
                            to_run.push(s);
                        }
                    }
                }

                // run statements with expressions (they have effects)
                ast::stmt_mac(*) | ast::stmt_semi(*) | ast::stmt_expr(*) => {
                    to_run.push(s);
                }
            }
        }
        result = do blk.node.expr.map_consume |e| {
            do with_pp(intr) |pp, _| { pprust::print_expr(pp, e); }
        };
    }
    // return fast for empty inputs
    if to_run.len() == 0 && result.is_none() {
        return repl;
    }

    //
    // Stage 2: run everything up to typeck to learn the types of the new
    //          variables introduced into the program
    //
    info!("Learning about the new types in the program");
    repl.program.set_cache(); // before register_new_vars (which changes them)
    let input = to_run.connect("\n");
    let test = repl.program.test_code(input, &result, *new_locals);
    debug!("testing with ^^^^^^ %?", (||{ println(test) })());
    let dinput = driver::str_input(test.to_managed());
    let cfg = driver::build_configuration(sess, binary, &dinput);
    let outputs = driver::build_output_filenames(&dinput, &None, &None, [], sess);
    let (crate, tcx) = driver::compile_upto(sess, copy cfg, &dinput,
                                            driver::cu_typeck, Some(outputs));
    // Once we're typechecked, record the types of all local variables defined
    // in this input
    do find_main(crate.expect("crate after cu_typeck"), sess) |blk| {
        repl.program.register_new_vars(blk, tcx.expect("tcx after cu_typeck"));
    }

    //
    // Stage 3: Actually run the code in the JIT
    //
    info!("actually running code");
    let code = repl.program.code(input, &result);
    debug!("actually running ^^^^^^ %?", (||{ println(code) })());
    let input = driver::str_input(code.to_managed());
    let cfg = driver::build_configuration(sess, binary, &input);
    let outputs = driver::build_output_filenames(&input, &None, &None, [], sess);
    let sess = driver::build_session(options, diagnostic::emit);
    driver::compile_upto(sess, cfg, &input, driver::cu_everything,
                         Some(outputs));

    //
    // Stage 4: Inform the program that computation is done so it can update all
    //          local variable bindings.
    //
    info!("cleaning up after code");
    repl.program.consume_cache();

    return repl;

    fn parse_input(sess: session::Session, binary: @str,
                   input: &str) -> @ast::crate {
        let code = fmt!("fn main() {\n %s \n}", input);
        let input = driver::str_input(code.to_managed());
        let cfg = driver::build_configuration(sess, binary, &input);
        let outputs = driver::build_output_filenames(&input, &None, &None, [], sess);
        let (crate, _) = driver::compile_upto(sess, cfg, &input,
                                              driver::cu_parse, Some(outputs));
        crate.expect("parsing should return a crate")
    }

    fn find_main(crate: @ast::crate, sess: session::Session,
                 f: &fn(&ast::blk)) {
        for crate.node.module.items.each |item| {
            match item.node {
                ast::item_fn(_, _, _, _, ref blk) => {
                    if item.ident == sess.ident_of("main") {
                        return f(blk);
                    }
                }
                _ => {}
            }
        }
        fail!("main function was expected somewhere...");
    }
}

// Compiles a crate given by the filename as a library if the compiled
// version doesn't exist or is older than the source file. Binary is
// the name of the compiling executable. Returns Some(true) if it
// successfully compiled, Some(false) if the crate wasn't compiled
// because it already exists and is newer than the source file, or
// None if there were compile errors.
fn compile_crate(src_filename: ~str, binary: ~str) -> Option<bool> {
    match do task::try {
        let src_path = Path(src_filename);
        let binary = binary.to_managed();
        let options = @session::options {
            binary: binary,
            addl_lib_search_paths: @mut ~[os::getcwd()],
            .. copy *session::basic_options()
        };
        let input = driver::file_input(copy src_path);
        let sess = driver::build_session(options, diagnostic::emit);
        *sess.building_library = true;
        let cfg = driver::build_configuration(sess, binary, &input);
        let outputs = driver::build_output_filenames(
            &input, &None, &None, [], sess);
        // If the library already exists and is newer than the source
        // file, skip compilation and return None.
        let mut should_compile = true;
        let dir = os::list_dir_path(&Path(outputs.out_filename.dirname()));
        let maybe_lib_path = do dir.find |file| {
            // The actual file's name has a hash value and version
            // number in it which is unknown at this time, so looking
            // for a file that matches out_filename won't work,
            // instead we guess which file is the library by matching
            // the prefix and suffix of out_filename to files in the
            // directory.
            let file_str = file.filename().get();
            file_str.starts_with(outputs.out_filename.filestem().get())
                && file_str.ends_with(outputs.out_filename.filetype().get())
        };
        match maybe_lib_path {
            Some(lib_path) => {
                let (src_mtime, _) = src_path.get_mtime().get();
                let (lib_mtime, _) = lib_path.get_mtime().get();
                if lib_mtime >= src_mtime {
                    should_compile = false;
                }
            },
            None => { },
        }
        if (should_compile) {
            println(fmt!("compiling %s...", src_filename));
            driver::compile_upto(sess, cfg, &input, driver::cu_everything,
                                 Some(outputs));
            true
        } else { false }
    } {
        Ok(true) => Some(true),
        Ok(false) => Some(false),
        Err(_) => None,
    }
}

/// Tries to get a line from rl after outputting a prompt. Returns
/// None if no input was read (e.g. EOF was reached).
fn get_line(use_rl: bool, prompt: &str) -> Option<~str> {
    if use_rl {
        let result = unsafe { rl::read(prompt) };

        match result {
            None => None,
            Some(line) => {
                unsafe { rl::add_history(line) };
                Some(line)
            }
        }
    } else {
        if io::stdin().eof() {
            None
        } else {
            Some(io::stdin().read_line())
        }
    }
}

/// Run a command, e.g. :clear, :exit, etc.
fn run_cmd(repl: &mut Repl, _in: @io::Reader, _out: @io::Writer,
           cmd: ~str, args: ~[~str], use_rl: bool) -> CmdAction {
    let mut action = action_none;
    match cmd {
        ~"exit" => repl.running = false,
        ~"clear" => {
            repl.program.clear();

            // XXX: Win32 version of linenoise can't do this
            //rl::clear();
        }
        ~"help" => {
            println(
                ":{\\n ..lines.. \\n:}\\n - execute multiline command\n\
                 :load <crate> ... - loads given crates as dynamic libraries\n\
                 :clear - clear the bindings\n\
                 :exit - exit from the repl\n\
                 :help - show this message");
        }
        ~"load" => {
            let mut loaded_crates: ~[~str] = ~[];
            for args.each |arg| {
                let (crate, filename) =
                    if arg.ends_with(".rs") || arg.ends_with(".rc") {
                    (arg.slice_to(arg.len() - 3).to_owned(), copy *arg)
                } else {
                    (copy *arg, *arg + ".rs")
                };
                match compile_crate(filename, copy repl.binary) {
                    Some(_) => loaded_crates.push(crate),
                    None => { }
                }
            }
            for loaded_crates.each |crate| {
                let crate_path = Path(*crate);
                let crate_dir = crate_path.dirname();
                repl.program.record_extern(fmt!("extern mod %s;", *crate));
                if !repl.lib_search_paths.contains(&crate_dir) {
                    repl.lib_search_paths.push(crate_dir);
                }
            }
            if loaded_crates.is_empty() {
                println("no crates loaded");
            } else {
                println(fmt!("crates loaded: %s",
                                 loaded_crates.connect(", ")));
            }
        }
        ~"{" => {
            let mut multiline_cmd = ~"";
            let mut end_multiline = false;
            while (!end_multiline) {
                match get_line(use_rl, "rusti| ") {
                    None => fail!("unterminated multiline command :{ .. :}"),
                    Some(line) => {
                        if line.trim() == ":}" {
                            end_multiline = true;
                        } else {
                            multiline_cmd += line + "\n";
                        }
                    }
                }
            }
            action = action_run_line(multiline_cmd);
        }
        _ => println(~"unknown cmd: " + cmd)
    }
    return action;
}

/// Executes a line of input, which may either be rust code or a
/// :command. Returns a new Repl if it has changed.
pub fn run_line(repl: &mut Repl, in: @io::Reader, out: @io::Writer, line: ~str,
                use_rl: bool)
    -> Option<Repl> {
    if line.starts_with(":") {
        // drop the : and the \n (one byte each)
        let full = line.slice(1, line.len());
        let split: ~[~str] = full.word_iter().transform(|s| s.to_owned()).collect();
        let len = split.len();

        if len > 0 {
            let cmd = copy split[0];

            if !cmd.is_empty() {
                let args = if len > 1 {
                    vec::slice(split, 1, len).to_vec()
                } else { ~[] };

                match run_cmd(repl, in, out, cmd, args, use_rl) {
                    action_none => { }
                    action_run_line(multiline_cmd) => {
                        if !multiline_cmd.is_empty() {
                            return run_line(repl, in, out, multiline_cmd, use_rl);
                        }
                    }
                }
                return None;
            }
        }
    }

    let line = Cell::new(line);
    let r = Cell::new(copy *repl);
    let result = do task::try {
        run(r.take(), line.take())
    };

    if result.is_ok() {
        return Some(result.get());
    }
    return None;
}

pub fn main() {
    let args = os::args();
    let in = io::stdin();
    let out = io::stdout();
    let mut repl = Repl {
        prompt: ~"rusti> ",
        binary: copy args[0],
        running: true,
        lib_search_paths: ~[],

        program: Program::new(),
    };

    let istty = unsafe { libc::isatty(libc::STDIN_FILENO as i32) } != 0;

    // only print this stuff if the user is actually typing into rusti
    if istty {
        println("WARNING: The Rust REPL is experimental and may be");
        println("unstable. If you encounter problems, please use the");
        println("compiler instead. Type :help for help.");

        unsafe {
            do rl::complete |line, suggest| {
                if line.starts_with(":") {
                    suggest(~":clear");
                    suggest(~":exit");
                    suggest(~":help");
                    suggest(~":load");
                }
            }
        }
    }

    while repl.running {
        match get_line(istty, repl.prompt) {
            None => break,
            Some(line) => {
                if line.is_empty() {
                    if istty {
                        println("()");
                    }
                    loop;
                }
                match run_line(&mut repl, in, out, line, istty) {
                    Some(new_repl) => repl = new_repl,
                    None => { }
                }
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use std::io;
    use std::iterator::IteratorUtil;
    use program::Program;
    use super::*;

    fn repl() -> Repl {
        Repl {
            prompt: ~"rusti> ",
            binary: ~"rusti",
            running: true,
            lib_search_paths: ~[],
            program: Program::new(),
        }
    }

    fn run_program(prog: &str) {
        let mut r = repl();
        for prog.split_iter('\n').advance |cmd| {
            let result = run_line(&mut r, io::stdin(), io::stdout(),
                                  cmd.to_owned(), false);
            r = result.expect(fmt!("the command '%s' failed", cmd));
        }
    }

    #[test]
    fn run_all() {
        // FIXME(#7071):
        // By default, unit tests are run in parallel. Rusti, on the other hand,
        // does not enjoy doing this. I suspect that it is because the LLVM
        // bindings are not thread-safe (when running parallel tests, some tests
        // were triggering assertions in LLVM (or segfaults). Hence, this
        // function exists to run everything serially (sadface).
        //
        // To get some interesting output, run with RUST_LOG=rusti::tests

        debug!("hopefully this runs");
        run_program("");

        debug!("regression test for #5937");
        run_program("use std::hashmap;");

        debug!("regression test for #5784");
        run_program("let a = 3;");

        // XXX: can't spawn new tasks because the JIT code is cleaned up
        //      after the main function is done.
        // debug!("regression test for #5803");
        // run_program("
        //     spawn( || println(\"Please don't segfault\") );
        //     do spawn { println(\"Please?\"); }
        // ");

        debug!("inferred integers are usable");
        run_program("let a = 2;\n()\n");
        run_program("
            let a = 3;
            let b = 4u;
            assert!((a as uint) + b == 7)
        ");

        debug!("local variables can be shadowed");
        run_program("
            let a = 3;
            let a = 5;
            assert!(a == 5)
        ");

        debug!("strings are usable");
        run_program("
            let a = ~\"\";
            let b = \"\";
            let c = @\"\";
            let d = a + b + c;
            assert!(d.len() == 0);
        ");

        debug!("vectors are usable");
        run_program("
            let a = ~[1, 2, 3];
            let b = &[1, 2, 3];
            let c = @[1, 2, 3];
            let d = a + b + c;
            assert!(d.len() == 9);
            let e: &[int] = [];
        ");

        debug!("structs are usable");
        run_program("
            struct A{ a: int }
            let b = A{ a: 3 };
            assert!(b.a == 3)
        ");

        debug!("mutable variables");
        run_program("
            let mut a = 3;
            a = 5;
            let mut b = std::hashmap::HashSet::new::<int>();
            b.insert(a);
            assert!(b.contains(&5))
            assert!(b.len() == 1)
        ");

        debug!("functions are cached");
        run_program("
            fn fib(x: int) -> int { if x < 2 {x} else { fib(x - 1) + fib(x - 2) } }
            let a = fib(3);
            let a = a + fib(4);
            assert!(a == 5)
        ");

        debug!("modules are cached");
        run_program("
            mod b { pub fn foo() -> uint { 3 } }
            assert!(b::foo() == 3)
        ");

        debug!("multiple function definitions are allowed");
        run_program("
            fn f() {}
            fn f() {}
            f()
        ");

        debug!("multiple item definitions are allowed");
        run_program("
            fn f() {}
            mod f {}
            struct f;
            enum f {}
            fn f() {}
            f()
        ");
    }

    #[test]
    fn exit_quits() {
        let mut r = repl();
        assert!(r.running);
        let result = run_line(&mut r, io::stdin(), io::stdout(),
                              ~":exit", false);
        assert!(result.is_none());
        assert!(!r.running);
    }
}