//! Write your own test scripts that look and behave like built-in tests!
//!
//! This is a simple and small testing framework that mimics the original
//! `libtest` (used by `cargo test`/`rustc --test`). That means: all output
//! looks pretty much like `cargo test` and most CLI arguments are understood
//! and used. With that plumbing work out of the way, your test runner can
//! concentrate on the actual testing.
//!
//! The central function of this crate is [`run_tests`].
//!
//! # Example
//!
//! ```
//! extern crate libtest_mimic;
//!
//! use libtest_mimic::{Arguments, Test, Outcome, run_tests};
//!
//!
//! // Parse command line arguments
//! let args = Arguments::from_args();
//!
//! // Create a list of tests (in this case: three dummy tests)
//! let tests = vec![
//!     Test::test("toph"),
//!     Test::test("sokka"),
//!     Test {
//!         name: "long_computation".into(),
//!         kind: "".into(),
//!         is_ignored: true,
//!         is_bench: false,
//!         data: (),
//!     },
//! ];
//!
//! // Run all tests and exit the application appropriatly (in this case, the
//! // test runner is a dummy runner which does nothing and says that all tests
//! // passed).
//! run_tests(&args, tests, |test| Outcome::Passed).exit();
//! ```
//!
//! For more examples, see [`examples/` in the repository][repo-examples].
//!
//!
//! [repo-examples]: https://github.com/LukasKalbertodt/libtest-mimic/tree/master/examples

use rayon::prelude::*;
use std::process;

mod args;
mod printer;

pub use crate::args::{Arguments, ColorSetting, FormatSetting};


/// Description of a single test.
#[derive(Clone, Debug)]
pub struct Test<D = ()> {
    /// The name of the test. It's displayed in the output and used for all
    /// kinds of filtering.
    pub name: String,

    /// Optional string to describe the kind of test. If this string is not
    /// empty, it is printed in brackets before the test name (e.g.
    /// `test [my-kind] test_name`).
    pub kind: String,

    /// Whether or not this test should be ignored. If the `--ignored` flag is
    /// set, ignored tests are executed, too.
    pub is_ignored: bool,

    /// Whether this test is actually a benchmark.
    pub is_bench: bool,

    /// Custom data. This field is not used by this library and can instead be
    /// used to store arbitrary data per test.
    pub data: D,
}

impl<D: Default> Test<D> {
    /// Creates a test with the given name, an empty `kind` and default data.
    /// The test is not ignored and is not a benchmark.
    pub fn test(name: impl Into<String>) -> Self {
        Self {
            name: name.into(),
            kind: String::new(),
            is_ignored: false,
            is_bench: false,
            data: D::default(),
        }
    }

    /// Creates a benchmark with the given name, an empty `kind` and default
    /// data. The benchmark is not ignored.
    pub fn bench(name: impl Into<String>) -> Self {
        Self {
            name: name.into(),
            kind: String::new(),
            is_ignored: false,
            is_bench: true,
            data: D::default(),
        }
    }
}

/// The outcome of performing a test.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum Outcome {
    /// The test passed.
    Passed,

    /// The test or benchmark failed (either compiler error or panicked).
    Failed {
        /// A message that is shown after all tests have been run.
        msg: Option<String>,
    },

    /// The test or benchmark was ignored.
    Ignored,

    /// The benchmark was successfully run.
    Measured {
        /// Average time in ns.
        avg: u64,
        /// Variance in ns.
        variance: u64,
    },
}

/// Event indicating that a given test has started running or has completed.
#[derive(Debug)]
pub enum RunnerEvent<D> {
    Started {
        /// Name of the corresponding test.
        name: String,
        /// Kind of the corresponding test.
        kind: String,
    },
    Completed {
        /// Corresponding test.
        test: Test<D>,
        /// Outcome of having run the test.
        outcome: Outcome,
    },
}

/// Contains information about the entire test run. Is returned by
/// [`run_tests`].
///
/// This type is marked as `#[must_use]`. Usually, you just call
/// [`exit()`][Conclusion::exit] on the result of `run_tests` to exit the application
/// with the correct exit code. But you can also store this value and inspect
/// its data.
#[derive(Clone, Debug)]
#[must_use]
pub struct Conclusion {
    has_failed: bool,
    num_filtered_out: u64,
    num_passed: u64,
    num_failed: u64,
    num_ignored: u64,
    num_benches: u64,
}

impl Conclusion {
    /// Exits the application with an appropriate error code (0 if all tests
    /// have passed, 101 if there have been failures).
    pub fn exit(&self) -> ! {
        self.exit_if_failed();
        process::exit(0);
    }

    /// Exits the application with error code 101 if there were any failures.
    /// Otherwise, returns normally.
    pub fn exit_if_failed(&self) {
        if self.has_failed {
            process::exit(101)
        }
    }

    /// Returns whether or not there have been any failures.
    pub fn has_failed(&self) -> bool {
        self.has_failed
    }

    /// Returns how many tests were filtered out (either by the filter-in
    /// pattern or by `--skip` arguments).
    pub fn num_filtered_out(&self) -> u64 {
        self.num_filtered_out
    }

    /// Returns how many tests passed.
    pub fn num_passed(&self) -> u64 {
        self.num_passed
    }

    /// Returns how many tests failed.
    pub fn num_failed(&self) -> u64 {
        self.num_failed
    }

    /// Returns how many tests were ignored.
    pub fn num_ignored(&self) -> u64 {
        self.num_ignored
    }

    /// Returns how many benchmark were successfully run.
    pub fn num_benches(&self) -> u64 {
        self.num_benches
    }
}

/// Run the given tests in parallel in a thread pool.
fn run_tests_threaded<D: 'static + Send + Sync>(
    args: &Arguments,
    tests: Vec<Test<D>>,
    run_test: impl Fn(&Test<D>) -> Outcome + 'static + Send + Sync,
) -> impl IntoIterator<Item = RunnerEvent<D>> {
    // Construct a pool with as many threads as specified.
    let mut builder = rayon::ThreadPoolBuilder::new();
    if let Some(n) = args.num_threads {
        builder = builder.num_threads(n);
    }
    let pool = builder.build().expect("Unable to spawn threads");

    // The spawned threads could outlive the calling function so we can't pass `args` as a
    // reference.
    let args = args.clone();

    // We will send the events through this channel.
    let (send, recv) = crossbeam_channel::bounded(0);

    // This spawns a thread on the pool and returns immediately.
    pool.spawn(move || {
        // This will split the workload across the thread pool automatically.
        tests.into_par_iter().for_each(|test| {
            // It doesn't matter if the channel got closed so we can ignore the Result here.
            let _ = send.send(RunnerEvent::Started {
                name: test.name.clone(),
                kind: test.kind.clone(),
            });

            let is_ignored = (test.is_ignored && !args.ignored)
                || (test.is_bench && args.test)
                || (!test.is_bench && args.bench);

            let outcome = if is_ignored {
                Outcome::Ignored
            } else {
                // Run the given function
                run_test(&test)
            };

            // It doesn't matter if the channel got closed so we can ignore the Result here.
            let _ = send.send(RunnerEvent::Completed { test, outcome });
        });
    });

    // Return the other end of the channel
    recv
}

/// Runs all given tests with the given test runner.
///
/// This is the central function of this crate. It provides the framework for
/// the testing harness. It does all the printing and house keeping.
///
/// This function tries to respect most options configured via CLI args. For
/// example, filtering, output format and coloring are respected. However, some
/// things cannot be handled by this function and *you* (as a user) need to
/// take care of it yourself. The following options are ignored by this
/// function and need to be manually checked:
///
/// - `--nocapture` and capturing in general. It is expected that during the
///   test, nothing writes to `stdout` and `stderr`, unless `--nocapture` was
///   specified. If the test is ran as a seperate process, this is fairly easy.
///   If however, the test is part of the current application and it uses
///   `println!()` and friends, it might be impossible to capture the output.
///
/// Currently, the following CLI arg is ignored, but is planned to be used
/// in the future:
/// - `--format=json`. If specified, this function will
///   panic.
///
/// All other flags and options are used properly.
///
/// The returned value contains a couple of useful information. See the
/// [`Conclusion`] documentation for more information. If `--list` was
/// specified, a list is printed and a dummy `Conclusion` is returned.
pub fn run_tests<D: 'static + Send + Sync>(
    args: &Arguments,
    tests: Vec<Test<D>>,
    run_test: impl Fn(&Test<D>) -> Outcome + 'static + Send + Sync,
) -> Conclusion {
    // Apply filtering
    let (tests, num_filtered_out) = if args.filter_string.is_some() || !args.skip.is_empty() {
        let len_before = tests.len() as u64;
        let mut tests = tests;
        tests.retain(|t| {
            // If a filter was specified, apply this
            if let Some(filter) = &args.filter_string {
                match args.exact {
                    true if &t.name != filter => return false,
                    false if !t.name.contains(filter) => return false,
                    _ => {}
                };
            }

            // If any skip pattern were specified, test for all patterns.
            for skip_filter in &args.skip {
                match args.exact {
                    true if &t.name == skip_filter => return false,
                    false if t.name.contains(skip_filter) => return false,
                    _ => {}
                }
            }

            true
        });

        let num_filtered_out = len_before - tests.len() as u64;
        (tests, num_filtered_out)
    } else {
        (tests, 0)
    };

    // Create printer which is used for all output.
    let mut printer = printer::Printer::new(args, &tests);

    // If `--list` is specified, just print the list and return.
    if args.list {
        printer.print_list(&tests, args.ignored);
        return Conclusion {
            has_failed: false,
            num_filtered_out: 0,
            num_passed: 0,
            num_failed: 0,
            num_ignored: 0,
            num_benches: 0,
        };
    }

    // Print number of tests
    printer.print_title(tests.len() as u64);

    let mut failed_tests = Vec::new();
    let mut num_ignored = 0;
    let mut num_benches = 0;
    let mut num_passed = 0;

    // Execute all tests
    for event in run_tests_threaded(args, tests, run_test) {
        match event {
            RunnerEvent::Started { name, kind } => {
                // If tests are being run sequentially, we print the test name
                // when it starts running and the result after it is done.
                // Otherwise we print both at the same time.
                if args.num_threads == Some(1) {
                    // Print `test foo    ...`.
                    printer.print_test(&name, &kind);
                }
            }
            RunnerEvent::Completed { test, outcome } => {
                if args.num_threads != Some(1) {
                    // Print `test foo    ...` if it hasn't already been printed.
                    printer.print_test(&test.name, &test.kind);
                }
                printer.print_single_outcome(&outcome);

                if test.is_bench {
                    num_benches += 1;
                }

                // Handle outcome
                match outcome {
                    Outcome::Passed => num_passed += 1,
                    Outcome::Failed { msg } => failed_tests.push((test, msg)),
                    Outcome::Ignored => num_ignored += 1,
                    Outcome::Measured { .. } => {}
                }
            }
        }
    }

    // Print failures if there were any
    if !failed_tests.is_empty() {
        printer.print_failures(&failed_tests);
    }

    // Handle overall results
    let num_failed = failed_tests.len() as u64;
    let conclusion = Conclusion {
        has_failed: num_failed != 0,
        num_filtered_out,
        num_passed,
        num_failed,
        num_ignored,
        num_benches,
    };

    printer.print_summary(&conclusion);

    conclusion
}