import type { FastifyInstance, FastifyReply, FastifyRequest } from "fastify";
import { z } from "zod";
import type { AppEnv } from "../config/env.js";
import {
  findFeature,
  listFeatureGroupsForProject as listFixtureFeatureGroupsForProject,
  listFeaturesForProject as listFixtureFeaturesForProject,
  paginate,
  type PaginationInput,
} from "../fixtures/featureFixtures.js";
import { findProject } from "../fixtures/projectFixtures.js";
import { getRequestId } from "../plugins/requestId.js";
import {
  listFeatureGroupsForProject as listDatabaseFeatureGroupsForProject,
} from "../repositories/featureGroupsRepository.js";
import {
  getFeatureBySlugOrId,
  listFeaturesForProject as listDatabaseFeaturesForProject,
  projectExists as databaseProjectExists,
} from "../repositories/featuresRepository.js";
import type { FeatureDto, FeatureStatus } from "../types/api.js";
import { errorEnvelope, successEnvelope } from "../utils/envelope.js";

const idSchema = z.string().min(1).regex(/^[a-z0-9-]+$/);

const projectParamsSchema = z.object({
  projectId: idSchema,
});

const featureParamsSchema = z.object({
  projectId: idSchema,
  featureId: idSchema,
});

const booleanQuerySchema = z.preprocess(
  (value) => {
    if (value === undefined || typeof value === "boolean") return value;
    if (typeof value !== "string") return undefined;
    const normalized = value.toLowerCase();
    if (["true", "1", "yes", "on"].includes(normalized)) return true;
    if (["false", "0", "no", "off"].includes(normalized)) return false;
    return undefined;
  },
  z.boolean().optional(),
);

const paginationQuerySchema = z.object({
  page: z.coerce.number().int().positive().default(1),
  pageSize: z.coerce.number().int().positive().max(100).default(25),
  cursor: z.string().optional(),
  sort: z.string().optional(),
});

const featuresQuerySchema = paginationQuerySchema.extend({
  status: z.string().optional(),
  confidence: z.coerce.number().int().min(0).max(100).optional(),
  hasEvidence: booleanQuerySchema,
  groupId: idSchema.optional(),
  search: z.string().optional(),
});

const sendValidationError = (
  request: FastifyRequest,
  reply: FastifyReply,
  validation: z.ZodIssue[],
) =>
  reply.status(400).send(
    errorEnvelope(
      "VALIDATION_ERROR",
      "Request validation failed",
      getRequestId(request),
      validation.map((issue) => ({
        field: issue.path.join("."),
        message: issue.message,
        code: issue.code,
      })),
    ),
  );

const parseParams = <TSchema extends z.ZodTypeAny>(
  schema: TSchema,
  request: FastifyRequest,
  reply: FastifyReply,
): z.output<TSchema> | undefined => {
  const parsed = schema.safeParse(request.params);

  if (!parsed.success) {
    sendValidationError(request, reply, parsed.error.issues);
    return undefined;
  }

  return parsed.data;
};

const parseQuery = <TSchema extends z.ZodTypeAny>(
  schema: TSchema,
  request: FastifyRequest,
  reply: FastifyReply,
): z.output<TSchema> | undefined => {
  const parsed = schema.safeParse(request.query);

  if (!parsed.success) {
    sendValidationError(request, reply, parsed.error.issues);
    return undefined;
  }

  return parsed.data;
};

const sendProjectNotFound = (
  request: FastifyRequest,
  reply: FastifyReply,
  projectId: string,
) =>
  reply.status(404).send(
    errorEnvelope(
      "PROJECT_NOT_FOUND",
      `Project '${projectId}' was not found.`,
      getRequestId(request),
    ),
  );

const splitCsv = (value: string | undefined): string[] =>
  value
    ?.split(",")
    .map((item) => item.trim())
    .filter(Boolean) ?? [];

const sortByField = <T extends Record<string, unknown>>(
  items: T[],
  sort: string | undefined,
): T[] => {
  if (!sort) return items;
  const [field, direction = "asc"] = sort.split(":");
  if (!field) return items;

  return [...items].sort((left, right) => {
    const leftValue = left[field];
    const rightValue = right[field];
    if (leftValue === rightValue) return 0;
    const comparison = String(leftValue ?? "").localeCompare(
      String(rightValue ?? ""),
      undefined,
      { numeric: true },
    );
    return direction === "desc" ? -comparison : comparison;
  });
};

type FeatureQuery = z.output<typeof featuresQuerySchema>;
type PaginationQuery = z.output<typeof paginationQuerySchema>;

const applyFeatureFilters = (
  features: FeatureDto[],
  query: FeatureQuery,
): FeatureDto[] => {
  const statuses = splitCsv(query.status) as FeatureStatus[];
  const normalizedSearch = query.search?.trim().toLowerCase();

  return features.filter((feature) => {
    if (statuses.length > 0 && !statuses.includes(feature.status)) return false;
    if (query.confidence !== undefined && feature.confidence !== query.confidence) {
      return false;
    }
    if (query.groupId !== undefined && feature.groupId !== query.groupId) {
      return false;
    }
    if (
      query.hasEvidence !== undefined &&
      (feature.evidenceIds.length > 0) !== query.hasEvidence
    ) {
      return false;
    }
    if (
      normalizedSearch &&
      !`${feature.name} ${feature.description}`
        .toLowerCase()
        .includes(normalizedSearch)
    ) {
      return false;
    }
    return true;
  });
};

const toPaginationInput = (
  query: PaginationQuery,
  filters: PaginationInput["filters"],
): PaginationInput => ({
  page: query.page,
  pageSize: query.pageSize,
  cursor: query.cursor,
  sort: query.sort,
  filters,
});

const ensureProject = async (
  request: FastifyRequest,
  reply: FastifyReply,
  projectId: string,
  useDatabase: boolean,
) => {
  const exists = useDatabase
    ? await databaseProjectExists(projectId)
    : Boolean(findProject(projectId));

  if (!exists) {
    sendProjectNotFound(request, reply, projectId);
    return false;
  }

  return true;
};

type FeatureRoutesOptions = {
  dataSource?: AppEnv["PROJECTBRAIN_DATA_SOURCE"];
};

export const registerFeatureRoutes = async (
  app: FastifyInstance,
  options: FeatureRoutesOptions = {},
) => {
  const useDatabase = options.dataSource === "database";

  app.get("/api/projects/:projectId/feature-groups", async (request, reply) => {
    const params = parseParams(projectParamsSchema, request, reply);
    if (!params) return reply;
    if (!(await ensureProject(request, reply, params.projectId, useDatabase))) {
      return reply;
    }

    const groups = useDatabase
      ? await listDatabaseFeatureGroupsForProject(params.projectId)
      : listFixtureFeatureGroupsForProject(params.projectId);

    return successEnvelope(groups ?? [], getRequestId(request));
  });

  app.get("/api/projects/:projectId/features", async (request, reply) => {
    const params = parseParams(projectParamsSchema, request, reply);
    if (!params) return reply;
    if (!(await ensureProject(request, reply, params.projectId, useDatabase))) {
      return reply;
    }

    const query = parseQuery(featuresQuerySchema, request, reply);
    if (!query) return reply;

    const filters = {
      ...(query.status ? { status: splitCsv(query.status) } : {}),
      ...(query.confidence !== undefined ? { confidence: query.confidence } : {}),
      ...(query.hasEvidence !== undefined ? { hasEvidence: query.hasEvidence } : {}),
      ...(query.groupId ? { groupId: query.groupId } : {}),
      ...(query.search ? { search: query.search } : {}),
      ...(query.cursor ? { cursor: query.cursor } : {}),
    };
    const sourceFeatures = useDatabase
      ? await listDatabaseFeaturesForProject(params.projectId)
      : listFixtureFeaturesForProject(params.projectId);
    const filteredFeatures = sortByField(
      applyFeatureFilters(sourceFeatures ?? [], query),
      query.sort,
    );

    return successEnvelope(
      paginate(filteredFeatures, toPaginationInput(query, filters)),
      getRequestId(request),
    );
  });

  app.get("/api/projects/:projectId/features/:featureId", async (request, reply) => {
    const params = parseParams(featureParamsSchema, request, reply);
    if (!params) return reply;
    if (!(await ensureProject(request, reply, params.projectId, useDatabase))) {
      return reply;
    }

    const feature = useDatabase
      ? await getFeatureBySlugOrId(params.projectId, params.featureId)
      : findFeature(params.projectId, params.featureId);
    if (!feature) {
      return reply.status(404).send(
        errorEnvelope(
          "FEATURE_NOT_FOUND",
          `Feature '${params.featureId}' was not found.`,
          getRequestId(request),
        ),
      );
    }

    return successEnvelope(feature, getRequestId(request));
  });
};