// SPDX-License-Identifier: MPL-2.0

use std::{collections::BTreeSet as Set, error::Error};

use pubgrub::error::PubGrubError;
use pubgrub::package::Package;
use pubgrub::range::Range;
use pubgrub::report::{DefaultStringReporter, Reporter};
use pubgrub::solver::{
    choose_package_with_fewest_versions, resolve, Dependencies, DependencyProvider,
    OfflineDependencyProvider,
};
use pubgrub::version::{NumberVersion, Version};

use proptest::collection::{btree_map, vec};
use proptest::prelude::*;
use proptest::sample::Index;
use proptest::string::string_regex;

use crate::sat_dependency_provider::SatResolve;

mod sat_dependency_provider;

/// The same as [OfflineDependencyProvider] but takes versions from the opposite end:
/// if [OfflineDependencyProvider] returns versions from newest to oldest, this returns them from oldest to newest.
#[derive(Clone)]
struct OldestVersionsDependencyProvider<P: Package, V: Version>(OfflineDependencyProvider<P, V>);

impl<P: Package, V: Version> DependencyProvider<P, V> for OldestVersionsDependencyProvider<P, V> {
    fn choose_package_version<T: std::borrow::Borrow<P>, U: std::borrow::Borrow<Range<V>>>(
        &self,
        potential_packages: impl Iterator<Item = (T, U)>,
    ) -> Result<(T, Option<V>), Box<dyn Error>> {
        Ok(choose_package_with_fewest_versions(
            |p| self.0.versions(p).into_iter().flatten().cloned(),
            potential_packages,
        ))
    }

    fn get_dependencies(&self, p: &P, v: &V) -> Result<Dependencies<P, V>, Box<dyn Error>> {
        self.0.get_dependencies(p, v)
    }
}

/// The same as DP but it has a timeout.
#[derive(Clone)]
struct TimeoutDependencyProvider<DP> {
    dp: DP,
    start_time: std::time::Instant,
    call_count: std::cell::Cell<u64>,
    max_calls: u64,
}

impl<DP> TimeoutDependencyProvider<DP> {
    fn new(dp: DP, max_calls: u64) -> Self {
        Self {
            dp,
            start_time: std::time::Instant::now(),
            call_count: std::cell::Cell::new(0),
            max_calls,
        }
    }
}

impl<P: Package, V: Version, DP: DependencyProvider<P, V>> DependencyProvider<P, V>
    for TimeoutDependencyProvider<DP>
{
    fn choose_package_version<T: std::borrow::Borrow<P>, U: std::borrow::Borrow<Range<V>>>(
        &self,
        potential_packages: impl Iterator<Item = (T, U)>,
    ) -> Result<(T, Option<V>), Box<dyn Error>> {
        self.dp.choose_package_version(potential_packages)
    }

    fn get_dependencies(&self, p: &P, v: &V) -> Result<Dependencies<P, V>, Box<dyn Error>> {
        self.dp.get_dependencies(p, v)
    }

    fn should_cancel(&self) -> Result<(), Box<dyn Error>> {
        assert!(self.start_time.elapsed().as_secs() < 60);
        let calls = self.call_count.get();
        assert!(calls < self.max_calls);
        self.call_count.set(calls + 1);
        Ok(())
    }
}

#[test]
#[should_panic]
fn should_cancel_can_panic() {
    let mut dependency_provider = OfflineDependencyProvider::<_, NumberVersion>::new();
    dependency_provider.add_dependencies(0, 0, vec![(666, Range::any())]);

    // Run the algorithm.
    let _ = resolve(
        &TimeoutDependencyProvider::new(dependency_provider, 1),
        0,
        0,
    );
}

fn string_names() -> impl Strategy<Value = String> {
    string_regex("[A-Za-z][A-Za-z0-9_-]{0,5}")
        .unwrap()
        .prop_filter("reserved names", |n| {
            // root is the name of the thing being compiled
            // so it would be confusing to have it in the index
            // bad is a name reserved for a dep that won't work
            n != "root" && n != "bad"
        })
}

/// This generates a random registry index.
/// Unlike vec((Name, Ver, vec((Name, VerRq), ..), ..)
/// This strategy has a high probability of having valid dependencies
pub fn registry_strategy<N: Package + Ord>(
    name: impl Strategy<Value = N>,
    bad_name: N,
) -> impl Strategy<
    Value = (
        OfflineDependencyProvider<N, NumberVersion>,
        Vec<(N, NumberVersion)>,
    ),
> {
    let max_crates = 40;
    let max_versions = 15;
    let shrinkage = 40;
    let complicated_len = 10usize;

    // If this is false than the crate will depend on the nonexistent "bad"
    // instead of the complex set we generated for it.
    let allow_deps = prop::bool::weighted(0.99);

    let a_version = ..(max_versions as u32);

    let list_of_versions = btree_map(a_version, allow_deps, 1..=max_versions)
        .prop_map(move |ver| ver.into_iter().collect::<Vec<_>>());

    let list_of_crates_with_versions = btree_map(name, list_of_versions, 1..=max_crates);

    // each version of each crate can depend on each crate smaller then it.
    // In theory shrinkage should be 2, but in practice we get better trees with a larger value.
    let max_deps = max_versions * (max_crates * (max_crates - 1)) / shrinkage;

    let raw_version_range = (any::<Index>(), any::<Index>());
    let raw_dependency = (any::<Index>(), any::<Index>(), raw_version_range);

    fn order_index(a: Index, b: Index, size: usize) -> (usize, usize) {
        use std::cmp::{max, min};
        let (a, b) = (a.index(size), b.index(size));
        (min(a, b), max(a, b))
    }

    let list_of_raw_dependency = vec(raw_dependency, ..=max_deps);

    // By default a package depends only on other packages that have a smaller name,
    // this helps make sure that all things in the resulting index are DAGs.
    // If this is true then the DAG is maintained with grater instead.
    let reverse_alphabetical = any::<bool>().no_shrink();

    (
        list_of_crates_with_versions,
        list_of_raw_dependency,
        reverse_alphabetical,
        1..(complicated_len + 1),
    )
        .prop_map(
            move |(crate_vers_by_name, raw_dependencies, reverse_alphabetical, complicated_len)| {
                let mut list_of_pkgid: Vec<(
                    (N, NumberVersion),
                    Option<Vec<(N, Range<NumberVersion>)>>,
                )> = crate_vers_by_name
                    .iter()
                    .flat_map(|(name, vers)| {
                        vers.iter().map(move |x| {
                            (
                                (name.clone(), NumberVersion::from(x.0)),
                                if x.1 { Some(vec![]) } else { None },
                            )
                        })
                    })
                    .collect();
                let len_all_pkgid = list_of_pkgid.len();
                for (a, b, (c, d)) in raw_dependencies {
                    let (a, b) = order_index(a, b, len_all_pkgid);
                    let (a, b) = if reverse_alphabetical { (b, a) } else { (a, b) };
                    let ((dep_name, _), _) = list_of_pkgid[a].to_owned();
                    if (list_of_pkgid[b].0).0 == dep_name {
                        continue;
                    }
                    let s = &crate_vers_by_name[&dep_name];
                    let s_last_index = s.len() - 1;
                    let (c, d) = order_index(c, d, s.len());

                    if let (_, Some(deps)) = &mut list_of_pkgid[b] {
                        deps.push((
                            dep_name,
                            if c == 0 && d == s_last_index {
                                Range::any()
                            } else if c == 0 {
                                Range::strictly_lower_than(s[d].0 + 1)
                            } else if d == s_last_index {
                                Range::higher_than(s[c].0)
                            } else if c == d {
                                Range::exact(s[c].0)
                            } else {
                                Range::between(s[c].0, s[d].0 + 1)
                            },
                        ))
                    }
                }

                let mut dependency_provider = OfflineDependencyProvider::<N, NumberVersion>::new();

                let complicated_len = std::cmp::min(complicated_len, list_of_pkgid.len());
                let complicated: Vec<_> = if reverse_alphabetical {
                    &list_of_pkgid[..complicated_len]
                } else {
                    &list_of_pkgid[(list_of_pkgid.len() - complicated_len)..]
                }
                .iter()
                .map(|(x, _)| (x.0.clone(), x.1))
                .collect();

                for ((name, ver), deps) in list_of_pkgid {
                    dependency_provider.add_dependencies(
                        name,
                        ver,
                        deps.unwrap_or_else(|| vec![(bad_name.clone(), Range::any())]),
                    );
                }

                (dependency_provider, complicated)
            },
        )
}

/// Ensures that generator makes registries with large dependency trees.
#[test]
fn meta_test_deep_trees_from_strategy() {
    use proptest::strategy::ValueTree;
    use proptest::test_runner::TestRunner;

    let mut dis = [0; 21];

    let strategy = registry_strategy(0u16..665, 666);
    let mut test_runner = TestRunner::deterministic();
    for _ in 0..128 {
        let (dependency_provider, cases) = strategy
            .new_tree(&mut TestRunner::new_with_rng(
                Default::default(),
                test_runner.new_rng(),
            ))
            .unwrap()
            .current();

        for (name, ver) in cases {
            let res = resolve(&dependency_provider, name, ver);
            dis[res
                .as_ref()
                .map(|x| std::cmp::min(x.len(), dis.len()) - 1)
                .unwrap_or(0)] += 1;
            if dis.iter().all(|&x| x > 0) {
                return;
            }
        }
    }

    panic!(
        "In {} tries we did not see a wide enough distribution of dependency trees! dis: {:?}",
        dis.iter().sum::<i32>(),
        dis
    );
}

proptest! {
    #![proptest_config(ProptestConfig {
    max_shrink_iters:
        if std::env::var("CI").is_ok() {
            // This attempts to make sure that CI will fail fast,
            0
        } else {
            // but that local builds will give a small clear test case.
            2048
        },
        result_cache: prop::test_runner::basic_result_cache,
        .. ProptestConfig::default()
    })]

    #[test]
    /// This test is mostly for profiling.
    fn prop_passes_string(
        (dependency_provider, cases) in registry_strategy(string_names(), "bad".to_owned())
    )  {
        for (name, ver) in cases {
            let _ = resolve(&TimeoutDependencyProvider::new(dependency_provider.clone(), 50_000), name, ver);
        }
    }

    #[test]
    /// This test is mostly for profiling.
    fn prop_passes_int(
        (dependency_provider, cases) in registry_strategy(0u16..665, 666)
    )  {
        for (name, ver) in cases {
            let _ = resolve(&TimeoutDependencyProvider::new(dependency_provider.clone(), 50_000), name, ver);
        }
    }

    #[test]
    fn prop_sat_errors_the_same(
        (dependency_provider, cases) in registry_strategy(0u16..665, 666)
    )  {
        let mut sat = SatResolve::new(&dependency_provider);
        for (name, ver) in cases {
            if let Ok(s) = resolve(&TimeoutDependencyProvider::new(dependency_provider.clone(), 50_000), name, ver) {
                prop_assert!(sat.sat_is_valid_solution(&s));
            } else {
                prop_assert!(!sat.sat_resolve(&name, &ver));
            }
        }
    }

    #[test]
    /// This tests whether the algorithm is still deterministic.
    fn prop_same_on_repeated_runs(
        (dependency_provider, cases) in registry_strategy(0u16..665, 666)
    )  {
        for (name, ver) in cases {
            let one = resolve(&TimeoutDependencyProvider::new(dependency_provider.clone(), 50_000), name, ver);
            for _ in 0..3 {
                match (&one, &resolve(&TimeoutDependencyProvider::new(dependency_provider.clone(), 50_000), name, ver)) {
                    (Ok(l), Ok(r)) => assert_eq!(l, r),
                    (Err(PubGrubError::NoSolution(derivation_l)), Err(PubGrubError::NoSolution(derivation_r))) => {
                        prop_assert_eq!(
                            DefaultStringReporter::report(&derivation_l),
                            DefaultStringReporter::report(&derivation_r)
                        )},
                    _ => panic!("not the same result")
                }
            }
        }
    }

    #[test]
    /// [ReverseDependencyProvider] changes what order the candidates
    /// are tried but not the existence of a solution.
    fn prop_reversed_version_errors_the_same(
        (dependency_provider, cases) in registry_strategy(0u16..665, 666)
    )  {
        let reverse_provider = OldestVersionsDependencyProvider(dependency_provider.clone());
        for (name, ver) in cases {
            let l = resolve(&TimeoutDependencyProvider::new(dependency_provider.clone(), 50_000), name, ver);
            let r = resolve(&TimeoutDependencyProvider::new(reverse_provider.clone(), 50_000), name, ver);
            match (&l, &r) {
                (Ok(_), Ok(_)) => (),
                (Err(_), Err(_)) => (),
                _ => panic!("not the same result")
            }
        }
    }

    #[test]
    fn prop_removing_a_dep_cant_break(
        (dependency_provider, cases) in registry_strategy(0u16..665, 666),
        indexes_to_remove in prop::collection::vec((any::<prop::sample::Index>(), any::<prop::sample::Index>(), any::<prop::sample::Index>()), 1..10)
    ) {
        let packages: Vec<_> = dependency_provider.packages().collect();
        let mut removed_provider = dependency_provider.clone();
        for (package_idx, version_idx, dep_idx) in indexes_to_remove {
            let package = package_idx.get(&packages);
            let versions: Vec<_> = dependency_provider
                .versions(package)
                .unwrap().collect();
            let version = version_idx.get(&versions);
            let dependencies: Vec<(u16, Range<NumberVersion>)> = match dependency_provider
                .get_dependencies(package, version)
                .unwrap()
            {
                Dependencies::Unknown => panic!(),
                Dependencies::Known(d) => d.into_iter().collect(),
            };
            if !dependencies.is_empty() {
                let dependency = dep_idx.get(&dependencies).0;
                removed_provider.add_dependencies(
                    **package,
                    **version,
                    dependencies.into_iter().filter(|x| x.0 != dependency),
                )
            }
        }
        for (name, ver) in cases {
            if resolve(
                &TimeoutDependencyProvider::new(dependency_provider.clone(), 50_000),
                name,
                ver,
            )
            .is_ok()
            {
                prop_assert!(
                    resolve(
                        &TimeoutDependencyProvider::new(removed_provider.clone(), 50_000),
                        name,
                        ver
                    )
                    .is_ok(),
                    "full index worked for `{} = \"={}\"` but removing some deps broke it!",
                    name,
                    ver,
                )
            }
        }
    }

    #[test]
    fn prop_limited_independence_of_irrelevant_alternatives(
        (dependency_provider, cases) in registry_strategy(0u16..665, 666),
        indexes_to_remove in prop::collection::vec(any::<prop::sample::Index>(), 1..10)
    )  {
        let all_versions: Vec<(u16, NumberVersion)> = dependency_provider
            .packages()
            .flat_map(|&p| {
                dependency_provider
                    .versions(&p)
                    .unwrap()
                    .map(move |v| (p, v.clone()))
            })
            .collect();
        let to_remove: Set<(_, _)> = indexes_to_remove.iter().map(|x| x.get(&all_versions)).cloned().collect();
        for (name, ver) in cases {
            match resolve(&TimeoutDependencyProvider::new(dependency_provider.clone(), 50_000), name, ver) {
                Ok(used) => {
                    // If resolution was successful, then unpublishing a version of a crate
                    // that was not selected should not change that.
                    let mut smaller_dependency_provider = OfflineDependencyProvider::<_, NumberVersion>::new();
                    for &(n, v) in &all_versions {
                        if used.get(&n) == Some(&v) // it was used
                           || to_remove.get(&(n, v)).is_none() // or it is not one to be removed
                        {
                            let deps = match dependency_provider.get_dependencies(&n, &v).unwrap() {
                                Dependencies::Unknown => panic!(),
                                Dependencies::Known(deps) => deps,
                            };
                            smaller_dependency_provider.add_dependencies(n, v, deps)
                        }
                    }
                    prop_assert!(
                        resolve(&TimeoutDependencyProvider::new(smaller_dependency_provider.clone(), 50_000), name, ver).is_ok(),
                        "unpublishing {:?} stopped `{} = \"={}\"` from working",
                        to_remove,
                        name,
                        ver
                    )
                }
                Err(_) => {
                    // If resolution was unsuccessful, then it should stay unsuccessful
                    // even if any version of a crate is unpublished.
                    let mut smaller_dependency_provider = OfflineDependencyProvider::<_, NumberVersion>::new();
                    for &(n, v) in &all_versions {
                        if to_remove.get(&(n, v)).is_none() // it is not one to be removed
                        {
                            let deps = match dependency_provider.get_dependencies(&n, &v).unwrap() {
                                Dependencies::Unknown => panic!(),
                                Dependencies::Known(deps) => deps,
                            };
                            smaller_dependency_provider.add_dependencies(n, v, deps)
                        }
                    }
                    prop_assert!(
                        resolve(&TimeoutDependencyProvider::new(smaller_dependency_provider.clone(), 50_000), name, ver).is_err(),
                        "full index did not work for `{} = \"={}\"` but unpublishing {:?} fixed it!",
                        name,
                        ver,
                        to_remove,
                    )
                }
            }
        }
    }
}

#[cfg(feature = "serde")]
#[test]
fn large_case() {
    for case in std::fs::read_dir("test-examples").unwrap() {
        let case = case.unwrap().path();
        let name = case.file_name().unwrap().to_string_lossy();
        eprintln!("{}", name);
        let data = std::fs::read_to_string(&case).unwrap();
        if name.ends_with("u16_NumberVersion.ron") {
            let dependency_provider: OfflineDependencyProvider<u16, NumberVersion> =
                ron::de::from_str(&data).unwrap();
            let mut sat = SatResolve::new(&dependency_provider);
            for p in dependency_provider.packages() {
                for n in dependency_provider.versions(p).unwrap() {
                    if let Ok(s) = resolve(&dependency_provider, p.clone(), n.clone()) {
                        assert!(sat.sat_is_valid_solution(&s));
                    } else {
                        assert!(!sat.sat_resolve(p, &n));
                    }
                }
            }
        } else if name.ends_with("str_SemanticVersion.ron") {
            let dependency_provider: OfflineDependencyProvider<
                &str,
                pubgrub::version::SemanticVersion,
            > = ron::de::from_str(&data).unwrap();
            let mut sat = SatResolve::new(&dependency_provider);
            for p in dependency_provider.packages() {
                for n in dependency_provider.versions(p).unwrap() {
                    if let Ok(s) = resolve(&dependency_provider, p.clone(), n.clone()) {
                        assert!(sat.sat_is_valid_solution(&s));
                    } else {
                        assert!(!sat.sat_resolve(p, &n));
                    }
                }
            }
        }
    }
}