import type { BodyRule, CheckFailure, CssRule, ExpectOperator, ExpectValue, JsonRule, XpathRule } from "../types";
import * as cheerio from "cheerio";
import * as xpath from "xpath";
import { DOMParser } from "@xmldom/xmldom";
import { mismatchFailure, errorFailure } from "./failure";

const isObject = (v: unknown): v is Record<string, unknown> => v !== null && typeof v === "object" && !Array.isArray(v);

export function evaluateJsonPath(json: unknown, path: string): unknown {
  if (!path.startsWith("$.")) return undefined;

  const segments = path.slice(2).split(".");
  let current: unknown = json;

  for (const seg of segments) {
    const bracketMatch = /^(.+?)\[(\d+)\]$/.exec(seg);
    if (bracketMatch) {
      current = (current as Record<string, unknown>)?.[bracketMatch[1]!];
      const idx = parseInt(bracketMatch[2]!, 10);
      if (!Array.isArray(current) || idx >= current.length) return undefined;
      current = current[idx];
    } else {
      if (current === null || current === undefined) return undefined;
      current = (current as Record<string, unknown>)[seg];
    }
  }

  return current;
}

export function applyOperator(actual: unknown, op: ExpectOperator): boolean {
  for (const [key, expected] of Object.entries(op)) {
    if (expected === undefined) continue;

    switch (key) {
      case "equals":
        if (actual !== expected) return false;
        break;
      case "contains":
        if (!String(actual).includes(expected as string)) return false;
        break;
      case "match":
        if (!new RegExp(expected as string).test(String(actual))) return false;
        break;
      case "empty": {
        const isEmpty =
          actual === null ||
          actual === undefined ||
          actual === "" ||
          (Array.isArray(actual) && actual.length === 0) ||
          (typeof actual === "object" && Object.keys(actual as object).length === 0);
        if (expected !== isEmpty) return false;
        break;
      }
      case "exists":
        if (expected) {
          if (actual === undefined) return false;
        } else {
          if (actual !== undefined) return false;
        }
        break;
      case "gte":
        if (!(Number(actual) >= (expected as number))) return false;
        break;
      case "lte":
        if (!(Number(actual) <= (expected as number))) return false;
        break;
      case "gt":
        if (!(Number(actual) > (expected as number))) return false;
        break;
      case "lt":
        if (!(Number(actual) < (expected as number))) return false;
        break;
    }
  }

  return true;
}

export function checkExpectValue(actual: unknown, expected: ExpectValue): boolean {
  if (isObject(expected)) {
    return applyOperator(actual, expected as ExpectOperator);
  }
  return applyOperator(actual, { equals: expected as string | number | boolean | null });
}

function checkJsonRule(
  body: string,
  rule: JsonRule,
  rulePath: string,
): { matched: boolean; failure: CheckFailure | null } {
  const { path, ...operators } = rule;
  const fullPath = `${rulePath}.json(${path})`;

  let json: unknown;
  try {
    json = JSON.parse(body);
  } catch {
    return {
      matched: false,
      failure: errorFailure("body", fullPath, "body is not valid JSON"),
    };
  }

  const actual = evaluateJsonPath(json, path);
  const opKeys = Object.keys(operators);

  if (opKeys.length === 0) {
    if (actual === undefined) {
      return {
        matched: false,
        failure: mismatchFailure("body", fullPath, "defined", actual, `path ${path} is undefined`),
      };
    }
    return { matched: true, failure: null };
  }

  const matched = applyOperator(actual, operators);
  if (!matched) {
    return {
      matched: false,
      failure: mismatchFailure("body", fullPath, operators, actual, `json path ${path} mismatch`),
    };
  }
  return { matched: true, failure: null };
}

function checkCssRule(
  body: string,
  rule: CssRule,
  rulePath: string,
): { matched: boolean; failure: CheckFailure | null } {
  const { selector, attr, ...operators } = rule;
  const fullPath = `${rulePath}.css(${selector}${attr ? `@${attr}` : ""})`;

  let $: cheerio.CheerioAPI;
  try {
    $ = cheerio.load(body);
  } catch {
    return {
      matched: false,
      failure: errorFailure("body", fullPath, "failed to parse HTML"),
    };
  }

  const el = $(selector);
  const opKeys = Object.keys(operators);

  if (opKeys.length === 0) {
    if (attr !== undefined) {
      if (el.attr(attr) === undefined) {
        return {
          matched: false,
          failure: mismatchFailure("body", fullPath, "attr present", undefined, `attribute ${attr} not found`),
        };
      }
      return { matched: true, failure: null };
    }
    if (el.length === 0) {
      return {
        matched: false,
        failure: mismatchFailure("body", fullPath, "element found", "no match", `selector ${selector} not found`),
      };
    }
    return { matched: true, failure: null };
  }

  if (operators.exists === true) {
    if (el.length === 0) {
      return {
        matched: false,
        failure: mismatchFailure("body", fullPath, true, false, `selector ${selector} not found`),
      };
    }
    return { matched: true, failure: null };
  }
  if (operators.exists === false) {
    if (el.length > 0) {
      return {
        matched: false,
        failure: mismatchFailure("body", fullPath, false, true, `selector ${selector} exists`),
      };
    }
    return { matched: true, failure: null };
  }

  if (el.length === 0) {
    return {
      matched: false,
      failure: mismatchFailure("body", fullPath, "element found", "no match", `selector ${selector} not found`),
    };
  }

  const actual = attr ? el.attr(attr) : el.text();
  const matched = applyOperator(actual ?? "", operators);
  if (!matched) {
    return {
      matched: false,
      failure: mismatchFailure("body", fullPath, operators, actual, `css selector ${selector} mismatch`),
    };
  }
  return { matched: true, failure: null };
}

function checkXpathRule(
  body: string,
  rule: XpathRule,
  rulePath: string,
): { matched: boolean; failure: CheckFailure | null } {
  const { path, ...operators } = rule;
  const fullPath = `${rulePath}.xpath(${path})`;

  let doc: ReturnType<DOMParser["parseFromString"]>;
  try {
    doc = new DOMParser().parseFromString(body, "text/xml");
  } catch {
    return {
      matched: false,
      failure: errorFailure("body", fullPath, "failed to parse XML/HTML"),
    };
  }

  const nodes = xpath.select(path, doc as unknown as Node);
  if (!nodes || !Array.isArray(nodes) || nodes.length === 0) {
    return {
      matched: false,
      failure: mismatchFailure("body", fullPath, "node found", "no match", `xpath ${path} not found`),
    };
  }

  const node = nodes[0]!;
  const actual = node.nodeValue ?? (node as unknown as Element).textContent ?? "";
  const opKeys = Object.keys(operators);

  if (opKeys.length === 0) {
    return { matched: true, failure: null };
  }

  const matched = applyOperator(actual, operators);
  if (!matched) {
    return {
      matched: false,
      failure: mismatchFailure("body", fullPath, operators, actual, `xpath ${path} mismatch`),
    };
  }
  return { matched: true, failure: null };
}

function checkSingleBodyRule(
  body: string,
  rule: BodyRule,
  index: number,
): { matched: boolean; failure: CheckFailure | null } {
  const rulePath = `body[${index}]`;

  if ("contains" in rule) {
    const matched = body.includes(rule.contains);
    if (!matched) {
      return {
        matched: false,
        failure: mismatchFailure("body", rulePath, rule.contains, body, `body does not contain "${rule.contains}"`),
      };
    }
    return { matched: true, failure: null };
  }

  if ("regex" in rule) {
    const matched = new RegExp(rule.regex).test(body);
    if (!matched) {
      return {
        matched: false,
        failure: mismatchFailure("body", rulePath, `/${rule.regex}/`, body, `body does not match /${rule.regex}/`),
      };
    }
    return { matched: true, failure: null };
  }

  if ("json" in rule) {
    return checkJsonRule(body, rule.json, rulePath);
  }

  if ("css" in rule) {
    return checkCssRule(body, rule.css, rulePath);
  }

  if ("xpath" in rule) {
    return checkXpathRule(body, rule.xpath, rulePath);
  }

  return { matched: true, failure: null };
}

export function checkBodyExpect(body: string, rules?: BodyRule[]): { matched: boolean; failure: CheckFailure | null } {
  if (!rules || rules.length === 0) return { matched: true, failure: null };

  for (let i = 0; i < rules.length; i++) {
    const result = checkSingleBodyRule(body, rules[i]!, i);
    if (!result.matched) return result;
  }

  return { matched: true, failure: null };
}