import React, { createContext, useContext, useEffect, useMemo, useRef, useState } from "react";
import { clearAuth, guessUsernameFromToken, jwtExpSeconds, loadAuth, saveAuth } from "./authStorage";

const AuthCtx = createContext(null);

function apiBase() {
  // même domaine par défaut
  return (import.meta?.env?.VITE_API_BASE_URL || "").replace(/\/+$/, "");
}

async function apiFetch(path, opts = {}) {
  const url = apiBase() + path;
  const res = await fetch(url, {
    ...opts,
    headers: {
      "Content-Type": "application/json",
      ...(opts.headers || {}),
    },
  });
  return res;
}

async function whoami(accessToken) {
  const res = await apiFetch("/api/whoami", {
    method: "GET",
    headers: accessToken ? { Authorization: `Bearer ${accessToken}` } : {},
  });
  const j = await res.json().catch(() => null);
  return { ok: res.ok, status: res.status, json: j };
}

async function refreshTokens(refreshToken) {
  const res = await apiFetch("/api/refresh", {
    method: "POST",
    body: JSON.stringify({ refresh_token: refreshToken }),
  });
  const j = await res.json().catch(() => null);
  return { ok: res.ok, status: res.status, json: j };
}

function nowSec() {
  return Math.floor(Date.now() / 1000);
}

export function AuthProvider({ children }) {
  const [status, setStatus] = useState("loading"); // loading | anon | auth
  const [user, setUser] = useState(null); // { username }
  const [tokens, setTokens] = useState(null); // { access_token, refresh_token, ... }
  const [error, setError] = useState("");
  const refreshTimer = useRef(null);

  function setAnon(msg = "") {
    setStatus("anon");
    setUser(null);
    setTokens(null);
    setError(msg || "");
    clearAuth();
  }

  function setAuthFromTokens(t, usernameGuess = "") {
    setTokens(t);
    saveAuth({ ...t, obtained_at: Date.now() });
    const u = usernameGuess || guessUsernameFromToken(t?.access_token) || "";
    setUser(u ? { username: u } : null);
    setStatus("auth");
    setError("");
  }

  async function ensureFreshSession(existing) {
    if (!existing?.access_token) return { ok: false, reason: "no_access_token" };

    const exp = jwtExpSeconds(existing.access_token);
    const skew = 60; // seconds
    const isExpiredOrSoon = !exp || exp <= (nowSec() + skew);

    // 1) refresh si nécessaire
    if (isExpiredOrSoon) {
      if (!existing.refresh_token) return { ok: false, reason: "expired_no_refresh" };

      const rr = await refreshTokens(existing.refresh_token);
      if (!rr.ok || !rr.json?.access_token) {
        return { ok: false, reason: `refresh_failed_${rr.status}` };
      }

      const merged = {
        ...existing,
        ...rr.json,
      };

      // certains serveurs renvoient pas refresh_token à chaque fois
      if (!merged.refresh_token) merged.refresh_token = existing.refresh_token;

      setAuthFromTokens(merged);
      existing = merged;
    } else {
      // access token encore bon
      setAuthFromTokens(existing);
    }

    // 2) confirmer avec backend (whoami)
    const w = await whoami(existing.access_token);
    if (w.ok && w.json?.authenticated) {
      const uname = w.json.username || guessUsernameFromToken(existing.access_token) || "";
      setUser(uname ? { username: uname } : null);
      setStatus("auth");
      setError("");
      return { ok: true };
    }

    // Si whoami fail, on considère désync (token invalide pour backend)
    return { ok: false, reason: `whoami_${w.status}` };
  }

  function scheduleAutoRefresh(t) {
    if (refreshTimer.current) {
      clearInterval(refreshTimer.current);
      refreshTimer.current = null;
    }
    // check aux 30s, refresh quand exp < 90s
    refreshTimer.current = setInterval(async () => {
      const cur = loadAuth();
      if (!cur?.access_token) return;

      const exp = jwtExpSeconds(cur.access_token);
      if (!exp) return;

      if (exp <= nowSec() + 90) {
        if (!cur.refresh_token) {
          setAnon("Session expirée (pas de refresh_token).");
          return;
        }
        const rr = await refreshTokens(cur.refresh_token);
        if (!rr.ok || !rr.json?.access_token) {
          setAnon("Session expirée. Please login again.");
          return;
        }
        const merged = { ...cur, ...rr.json };
        if (!merged.refresh_token) merged.refresh_token = cur.refresh_token;
        setAuthFromTokens(merged);
      }
    }, 30000);
  }

  async function restore() {
    setStatus("loading");
    setError("");
    const saved = loadAuth();
    if (!saved?.access_token) {
      setAnon("");
      return;
    }

    const r = await ensureFreshSession(saved);
    if (!r.ok) {
      setAnon("Login desynced. Please login again.");
      return;
    }

    scheduleAutoRefresh(saved);
  }

  async function login(username, password) {
    setError("");
    setStatus("loading");

    const res = await apiFetch("/api/login", {
      method: "POST",
      body: JSON.stringify({ username, password }),
    });

    const j = await res.json().catch(() => null);
    if (!res.ok || !j?.access_token) {
      setAnon(j?.error_description || j?.error || "Login failed");
      return { ok: false, status: res.status, json: j };
    }

    const t = {
      ...j,
      obtained_at: Date.now(),
    };

    setAuthFromTokens(t);
    scheduleAutoRefresh(t);

    // confirm whoami (si ça fail -> desync)
    const w = await whoami(t.access_token);
    if (!w.ok || !w.json?.authenticated) {
      setAnon("Login desynced. Please login again.");
      return { ok: false, status: w.status, json: w.json };
    }

    const uname = w.json.username || guessUsernameFromToken(t.access_token) || "";
    setUser(uname ? { username: uname } : null);
    setStatus("auth");
    return { ok: true };
  }

  function logout() {
    if (refreshTimer.current) clearInterval(refreshTimer.current);
    refreshTimer.current = null;
    setAnon("");
  }

  useEffect(() => {
    restore();

    const onStorage = (e) => {
      if (e.key === "sociowire:auth") restore();
    };
    window.addEventListener("storage", onStorage);
    return () => window.removeEventListener("storage", onStorage);
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  useEffect(() => {
    if (status === "auth" && tokens?.access_token) {
      scheduleAutoRefresh(tokens);
    }
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [status]);

  const value = useMemo(() => {
    return {
      status,
      user,
      tokens,
      error,

      isAuthed: status === "auth",
      accessToken: tokens?.access_token || "",

      login,
      logout,
      restore,
      setError,
    };
  }, [status, user, tokens, error]);

  return <AuthCtx.Provider value={value}>{children}</AuthCtx.Provider>;
}

export function useAuth() {
  return useContext(AuthCtx);
}
