using Invercargill;
using Invercargill.DataStructures;

namespace Usm {

    public class Resolver {

        private Dictionary<Repository, RepositoryListing> listings = new Dictionary<Repository, RepositoryListing>();
        private Set<AbstractPackage> supplied = new HashSet<AbstractPackage>();

        private Enumerable<AbstractPackage> available_packages() {
            return 
                supplied.concat(listings
                    .select_many<Pair<Repository, RepositoryListingEntry>>(l => l.value.entries.select_pairs<Repository, RepositoryListingEntry>(e => l.key, e => e))
                    .select<AbstractPackage>(p => new AbstractPackage.from_repository(p.value1, p.value2)));
        }

        public void load_listing(Repository repo, RepositoryListing listing) {
            listings.set(repo, listing);
        }

        public void supply_package(string path) throws Error {
            supplied.add(new AbstractPackage.from_package(path));
        }

        public void load_cache(Paths paths) throws Error {
            var state = new SystemState(paths);
            foreach (var package in state.get_cached_packages()) {
                supply_package(package.package_path);
            }
        }

        public AbstractPackage? find_package(string search) {
            return available_packages()
                .first_or_default(p => p.manifest.name == search);
        }

        public AbstractPackage? find_resource(ResourceRef resource) {
            return available_packages()
                .first_or_default(p => p.manifest.provides.any(r => resource.satisfied_by(r.key)));
        }

        public void solve_dependencies_for(PackageSet package_set) {
            var queue = new Fifo<AbstractPackage>();
            package_set.iterate(i => queue.push(i));

            foreach (var item in queue) {
                var dependencies = item.manifest.dependencies.build
                    .concat(item.manifest.dependencies.manage)
                    .concat(item.manifest.dependencies.runtime);

                foreach (var dep in dependencies) {
                    if(package_set.provides(dep) || dep.is_satisfied()) {
                        continue;
                    }

                    var provider = find_resource(dep);
                    if(provider == null) {
                        error(@"Could not solve dependency $dep");
                    }

                    package_set.add(provider);
                    queue.push(provider);
                }
            }
        }

    }

    public class PackageSet : HashSet<AbstractPackage> {

        public void add_from_file(string path) throws Error {
            add(new AbstractPackage.from_package(path));
        }

        public void add_from_repo(Repository repository, RepositoryListingEntry entry) throws Error {
            add(new AbstractPackage.from_repository(repository, entry));
        }

        public bool is_satisfied() {
            return all(check_satisfied);
        }

        private bool check_satisfied(AbstractPackage package) {
            return package.manifest.dependencies.build.all(d => provides(d) || d.is_satisfied()) &&
                package.manifest.dependencies.manage.all(d => provides(d) || d.is_satisfied()) &&
                package.manifest.dependencies.runtime.all(d => provides(d) || d.is_satisfied());

        }

        public bool provides(ResourceRef resource) {
            return any(p => p.manifest.provides.any(r => resource.satisfied_by(r.key)));
        }

    }

    public class AbstractPackage {

        public Manifest manifest { get; set; }
        public Repository? repository { get; set; }
        public RepositoryListingEntry? repository_entry { get; set; }
        public string? package_path { get; set; }
        public CachedPackage? cached_package { get; set; }

        public AbstractPackage.from_package(string path) throws Error {
            package_path = path;
            manifest = new Manifest.from_file(path);
        }

        public AbstractPackage.from_repository(Repository repository, RepositoryListingEntry entry) {
            this.repository = repository;
            this.repository_entry = entry;
            this.manifest = entry.manifest;
        }

    }

}