import fs from "fs";
import path from "path";
import type { AddressIntent, AddressResultMode } from "../types/addressQuery";

export type AddressRouteExpectationStatus = "matched" | "mismatch" | "not_found";

export interface AddressRouteExpectationEntry {
  intent: AddressIntent;
  expected_selected_recipes: string[];
  expected_requested_result_modes?: AddressResultMode[];
  expected_result_modes?: AddressResultMode[];
}

export interface AddressRouteExpectationsContract {
  schema_version: "address_route_expectations_v1";
  updated_at: string;
  entries: AddressRouteExpectationEntry[];
}

export interface AddressRouteExpectationAudit {
  status: AddressRouteExpectationStatus;
  reason: string;
  expected_selected_recipes: string[];
  expected_requested_result_modes: AddressResultMode[];
  expected_result_modes: AddressResultMode[];
}

const EXPECTATIONS_FILE = path.resolve(__dirname, "..", "..", "..", "..", "docs", "TECH", "address_route_expectations_v1.json");

function toObject(value: unknown): Record<string, unknown> | null {
  if (!value || typeof value !== "object" || Array.isArray(value)) {
    return null;
  }
  return value as Record<string, unknown>;
}

function toNonEmptyString(value: unknown): string | null {
  if (typeof value !== "string") {
    return null;
  }
  const trimmed = value.trim();
  return trimmed.length > 0 ? trimmed : null;
}

function toStringArray(value: unknown): string[] {
  if (!Array.isArray(value)) {
    return [];
  }
  return value.map((item) => toNonEmptyString(item)).filter((item): item is string => Boolean(item));
}

function parseResultModes(value: unknown): AddressResultMode[] {
  const raw = toStringArray(value);
  return raw.filter((mode): mode is AddressResultMode => mode === "heuristic_candidates" || mode === "confirmed_balance");
}

function parseEntry(value: unknown): AddressRouteExpectationEntry | null {
  const object = toObject(value);
  if (!object) {
    return null;
  }
  const intent = toNonEmptyString(object.intent) as AddressIntent | null;
  const expectedSelectedRecipes = toStringArray(object.expected_selected_recipes);
  if (!intent || expectedSelectedRecipes.length === 0) {
    return null;
  }
  const expectedRequestedResultModes = parseResultModes(object.expected_requested_result_modes);
  const expectedResultModes = parseResultModes(object.expected_result_modes);
  return {
    intent,
    expected_selected_recipes: expectedSelectedRecipes,
    ...(expectedRequestedResultModes.length > 0 ? { expected_requested_result_modes: expectedRequestedResultModes } : {}),
    ...(expectedResultModes.length > 0 ? { expected_result_modes: expectedResultModes } : {})
  };
}

export function loadAddressRouteExpectationsContract(): AddressRouteExpectationsContract {
  const raw = fs.readFileSync(EXPECTATIONS_FILE, "utf-8");
  const parsed = JSON.parse(raw) as unknown;
  const root = toObject(parsed);
  if (!root) {
    throw new Error("address_route_expectations_v1: invalid root payload");
  }
  const schemaVersion = toNonEmptyString(root.schema_version);
  if (schemaVersion !== "address_route_expectations_v1") {
    throw new Error(`address_route_expectations_v1: unexpected schema version '${schemaVersion ?? "null"}'`);
  }
  const updatedAt = toNonEmptyString(root.updated_at) ?? new Date().toISOString();
  const entriesRaw = Array.isArray(root.entries) ? root.entries : [];
  const entries = entriesRaw.map(parseEntry).filter((entry): entry is AddressRouteExpectationEntry => entry !== null);
  if (entries.length === 0) {
    throw new Error("address_route_expectations_v1: no valid entries");
  }
  return {
    schema_version: "address_route_expectations_v1",
    updated_at: updatedAt,
    entries
  };
}

export function evaluateAddressRouteExpectation(input: {
  intent: AddressIntent;
  selectedRecipe: string | null;
  requestedResultMode?: AddressResultMode;
  resultMode?: AddressResultMode;
}): AddressRouteExpectationAudit {
  const contract = loadAddressRouteExpectationsContract();
  const entry = contract.entries.find((item) => item.intent === input.intent);
  if (!entry) {
    return {
      status: "not_found",
      reason: "route_expectation_not_defined_for_intent",
      expected_selected_recipes: [],
      expected_requested_result_modes: [],
      expected_result_modes: []
    };
  }
  if (input.selectedRecipe && !entry.expected_selected_recipes.includes(input.selectedRecipe)) {
    return {
      status: "mismatch",
      reason: "selected_recipe_mismatch",
      expected_selected_recipes: entry.expected_selected_recipes,
      expected_requested_result_modes: entry.expected_requested_result_modes ?? [],
      expected_result_modes: entry.expected_result_modes ?? []
    };
  }
  if (
    input.requestedResultMode &&
    Array.isArray(entry.expected_requested_result_modes) &&
    entry.expected_requested_result_modes.length > 0 &&
    !entry.expected_requested_result_modes.includes(input.requestedResultMode)
  ) {
    return {
      status: "mismatch",
      reason: "requested_result_mode_mismatch",
      expected_selected_recipes: entry.expected_selected_recipes,
      expected_requested_result_modes: entry.expected_requested_result_modes,
      expected_result_modes: entry.expected_result_modes ?? []
    };
  }
  if (
    input.resultMode &&
    Array.isArray(entry.expected_result_modes) &&
    entry.expected_result_modes.length > 0 &&
    !entry.expected_result_modes.includes(input.resultMode)
  ) {
    return {
      status: "mismatch",
      reason: "result_mode_mismatch",
      expected_selected_recipes: entry.expected_selected_recipes,
      expected_requested_result_modes: entry.expected_requested_result_modes ?? [],
      expected_result_modes: entry.expected_result_modes
    };
  }
  return {
    status: "matched",
    reason: "route_expectation_matched",
    expected_selected_recipes: entry.expected_selected_recipes,
    expected_requested_result_modes: entry.expected_requested_result_modes ?? [],
    expected_result_modes: entry.expected_result_modes ?? []
  };
}