package api;

import static org.springframework.hateoas.server.mvc.WebMvcLinkBuilder.linkTo;
import static org.springframework.hateoas.server.mvc.WebMvcLinkBuilder.methodOn;

import java.util.Comparator;
import java.util.List;
import java.util.regex.Pattern;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.hateoas.Link;
import org.springframework.hateoas.server.LinkRelationProvider;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.security.web.access.WebInvocationPrivilegeEvaluator;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import com.google.common.collect.ImmutableList;

import resources.IndexResource;
import util.SuppressFBWarnings;

@RestController
@RequestMapping(value = ApiRestController.API_MAPPING)
public class ApiRestController {
    protected final Logger logger = LoggerFactory.getLogger(getClass());

    public static final String API_MAPPING = "/api";

    private static final Pattern ADMIN_REL_PREFIX_PATTERN = Pattern.compile("admin:", Pattern.LITERAL);
    private static final Pattern ADMIN_REL_QUERY_BUILDER_FORM_PATTERN = Pattern.compile("query-builder-form", Pattern.LITERAL);

    protected static final Comparator<Link> ADMIN_LINK_REL_COMPARATOR = Comparator.comparing(link -> link.getRel().value(), (rel1, rel2) -> {
        rel1 = ADMIN_REL_PREFIX_PATTERN.matcher(rel1).replaceFirst("");
        rel1 = ADMIN_REL_QUERY_BUILDER_FORM_PATTERN.matcher(rel1).replaceFirst("");
        rel2 = ADMIN_REL_PREFIX_PATTERN.matcher(rel2).replaceFirst("");
        rel2 = ADMIN_REL_QUERY_BUILDER_FORM_PATTERN.matcher(rel2).replaceFirst("");
        return rel1.compareTo(rel2);
    });

    private final WebInvocationPrivilegeEvaluator webPrivilegeEvaluator;
    private final List<ApiRootAdminRestController> adminRestControllers;

    @Autowired
    public ApiRestController(LinkRelationProvider rels,
                             WebInvocationPrivilegeEvaluator webPrivilegeEvaluator,
                             List<ApiRootAdminRestController> adminRestControllers) {

        this.webPrivilegeEvaluator = webPrivilegeEvaluator;
        this.adminRestControllers = adminRestControllers;
    }

    @RequestMapping(value = "", method = RequestMethod.GET, produces = {"application/hal+json", "application/json"})
    public ResponseEntity<IndexResource> api() {
        IndexResource resource = new IndexResource("index", null);
        resource.add(linkTo(ApiRestController.class).withSelfRel());

        Authentication authentication = SecurityContextHolder.getContext().getAuthentication();

        ImmutableList.Builder<Link> adminResourceLinks = ImmutableList.builder();

        for (ApiRootAdminRestController adminRestController : adminRestControllers) {
            if (webPrivilegeEvaluator.isAllowed(adminRestController.apiRootMapping(), authentication)) {
                adminRestController.queryBuilderFormLink().ifPresent(link -> adminResourceLinks.add(link));
                adminRestController.templatedLinkToItemPermalink().ifPresent(link -> adminResourceLinks.add(link));
                adminResourceLinks.addAll(adminRestController.miscRootLinks());
            }
        }

        adminResourceLinks.add(linkToTranslations());

        resource.add(ImmutableList.sortedCopyOf(
                ADMIN_LINK_REL_COMPARATOR,
                adminResourceLinks.build())
        );

        return new ResponseEntity<>(resource, HttpStatus.OK);
    }

    @SuppressWarnings("null")
    @SuppressFBWarnings(value = "NP_NONNULL_PARAM_VIOLATION", justification = "Not a real method call")
    private Link linkToTranslations() {
        return linkTo(methodOn(JsonTranslationController.class).get(null, null, null)).withRel(LinkRelation.of("translate"));
    }
}