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//-
// Copyright 2017, 2018 The proptest developers
//
// 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.

use std::env;
use std::ffi::OsString;

use test_runner::FailurePersistence;

const CASES: &str = "PROPTEST_CASES";
const MAX_LOCAL_REJECTS: &str = "PROPTEST_MAX_LOCAL_REJECTS";
const MAX_GLOBAL_REJECTS: &str = "PROPTEST_MAX_GLOBAL_REJECTS";
const MAX_FLAT_MAP_REGENS: &str = "PROPTEST_MAX_FLAT_MAP_REGENS";

/// The default config, computed by combining environment variables and
/// defaults.
lazy_static! {
    static ref DEFAULT_CONFIG: Config = {
        let mut result = Config {
            cases: 256,
            max_local_rejects: 65_536,
            max_global_rejects: 1024,
            max_flat_map_regens: 1_000_000,
            failure_persistence: FailurePersistence::default(),
            _non_exhaustive: (),
        };

        fn parse_or_warn(src: &OsString, dst: &mut u32, var: &str) {
            if let Some(src) = src.to_str() {
                if let Ok(value) = src.parse() {
                    *dst = value;
                } else {
                    eprintln!(
                        "proptest: The env-var {}={} can't be parsed as u32, \
                         using default of {}.", var, src, *dst);
                }
            } else {
                eprintln!(
                    "proptest: The env-var {} is not valid, using \
                     default of {}.", var, *dst);
            }
        }

        for (var, value) in env::vars_os() {
            if let Some(var) = var.to_str() {
                match var {
                    CASES => parse_or_warn(&value,
                        &mut result.cases, CASES),
                    MAX_LOCAL_REJECTS => parse_or_warn(&value,
                        &mut result.max_local_rejects, MAX_LOCAL_REJECTS),
                    MAX_GLOBAL_REJECTS => parse_or_warn(&value,
                        &mut result.max_global_rejects, MAX_GLOBAL_REJECTS),
                    MAX_FLAT_MAP_REGENS => parse_or_warn(&value,
                        &mut result.max_flat_map_regens, MAX_FLAT_MAP_REGENS),
                    _ => if var.starts_with("PROPTEST_") {
                        eprintln!("proptest: Ignoring unknown env-var {}.",
                                  var);
                    },
                }
            }
        }

        result
    };
}

/// Configuration for how a proptest test should be run.
#[derive(Clone, Debug, PartialEq)]
pub struct Config {
    /// The number of successful test cases that must execute for the test as a
    /// whole to pass.
    ///
    /// This does not include implicitly-replayed persisted failing cases.
    ///
    /// The default is 256, which can be overridden by setting the
    /// `PROPTEST_CASES` environment variable.
    pub cases: u32,
    /// The maximum number of individual inputs that may be rejected before the
    /// test as a whole aborts.
    ///
    /// The default is 65536, which can be overridden by setting the
    /// `PROPTEST_MAX_LOCAL_REJECTS` environment variable.
    pub max_local_rejects: u32,
    /// The maximum number of combined inputs that may be rejected before the
    /// test as a whole aborts.
    ///
    /// The default is 1024, which can be overridden by setting the
    /// `PROPTEST_MAX_GLOBAL_REJECTS` environment variable.
    pub max_global_rejects: u32,
    /// The maximum number of times all `Flatten` combinators will attempt to
    /// regenerate values. This puts a limit on the worst-case exponential
    /// explosion that can happen with nested `Flatten`s.
    ///
    /// The default is 1_000_000, which can be overridden by setting the
    /// `PROPTEST_MAX_FLAT_MAP_REGENS` environment variable.
    pub max_flat_map_regens: u32,
    /// Indicates how to determine the file to use for persisting failed test
    /// results.
    ///
    /// See the docs of [`FailurePersistence`](enum.FailurePersistence.html)
    /// for more information.
    ///
    /// The default is `FailurePersistence::SourceParallel("proptest-regressions")`.
    /// The default cannot currently be overridden by an environment variable.
    pub failure_persistence: FailurePersistence,
    // Needs to be public so FRU syntax can be used.
    #[doc(hidden)]
    pub _non_exhaustive: (),
}

impl Config {
    /// Constructs a `Config` only differing from the `default()` in the
    /// number of test cases required to pass the test successfully.
    ///
    /// This is simply a more concise alternative to using field-record update
    /// syntax:
    ///
    /// ```
    /// # use proptest::test_runner::Config;
    /// assert_eq!(
    ///     Config::with_cases(42),
    ///     Config { cases: 42, .. Config::default() }
    /// );
    /// ```
    pub fn with_cases(cases: u32) -> Self {
        Self { cases, .. Config::default() }
    }
}

impl Default for Config {
    fn default() -> Self {
        DEFAULT_CONFIG.clone()
    }
}