package eu.faircode.email;

/*
    This file is part of FairEmail.

    FairEmail is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    FairEmail is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with FairEmail.  If not, see <http://www.gnu.org/licenses/>.

    Copyright 2018-2024 by Marcel Bokhorst (M66B)
*/

import android.content.ContentResolver;
import android.content.Context;
import android.content.Intent;
import android.graphics.Typeface;
import android.net.Uri;
import android.os.Bundle;
import android.text.SpannableStringBuilder;
import android.text.Spanned;
import android.text.style.ForegroundColorSpan;
import android.text.style.RelativeSizeSpan;
import android.text.style.StyleSpan;
import android.text.style.TypefaceSpan;
import android.util.Pair;
import android.view.LayoutInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.constraintlayout.widget.Group;

import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import org.xmlpull.v1.XmlPullParserFactory;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.nio.charset.StandardCharsets;
import java.text.DateFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Locale;

public class ActivityDMARC extends ActivityBase {
    private TextView tvDmarc;
    private ContentLoadingProgressBar pbWait;
    private Group grpReady;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setSubtitle(R.string.title_advanced_dmarc_viewer);

        View view = LayoutInflater.from(this).inflate(R.layout.activity_dmarc, null);
        setContentView(view);

        tvDmarc = findViewById(R.id.tvDmarc);
        pbWait = findViewById(R.id.pbWait);
        grpReady = findViewById(R.id.grpReady);

        // Initialize
        FragmentDialogTheme.setBackground(this, view, false);
        grpReady.setVisibility(View.GONE);

        load();
    }

    @Override
    protected void onNewIntent(Intent intent) {
        super.onNewIntent(intent);
        setIntent(intent);
        load();
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int itemId = item.getItemId();
        if (itemId == android.R.id.home) {
            finish();
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    private void load() {
        Intent intent = getIntent();
        Uri uri = intent.getData();
        long id = intent.getLongExtra("id", -1L);
        Log.i("DMARC uri=" + uri + " id=" + id);

        Bundle args = new Bundle();
        args.putParcelable("uri", uri);
        args.putLong("id", id);

        new SimpleTask<Spanned>() {
            @Override
            protected void onPreExecute(Bundle args) {
                pbWait.setVisibility(View.VISIBLE);
            }

            @Override
            protected void onPostExecute(Bundle args) {
                pbWait.setVisibility(View.GONE);
            }

            @Override
            protected Spanned onExecute(Context context, Bundle args) throws Throwable {
                Uri uri = args.getParcelable("uri");
                NoStreamException.check(uri, context);

                SpannableStringBuilder ssb;
                ContentResolver resolver = context.getContentResolver();

                try (InputStream is = resolver.openInputStream(uri)) {
                    if (is == null)
                        throw new FileNotFoundException(uri.toString());
                    ssb = new Loader().load(context, is);
                }

                try (InputStream is = resolver.openInputStream(uri)) {
                    int start = ssb.length();
                    ssb.append(TextHelper.formatXml(Helper.readStream(is), 2));
                    ssb.setSpan(new TypefaceSpan("monospace"), start, ssb.length(), 0);
                    ssb.setSpan(new RelativeSizeSpan(HtmlHelper.FONT_SMALL), start, ssb.length(), 0);
                }

                return ssb;
            }

            @Override
            protected void onExecuted(Bundle args, Spanned dmarc) {
                tvDmarc.setText(dmarc);
                grpReady.setVisibility(View.VISIBLE);
            }

            @Override
            protected void onException(Bundle args, @NonNull Throwable ex) {
                if (ex instanceof NoStreamException)
                    ((NoStreamException) ex).report(ActivityDMARC.this);
                else
                    Log.unexpectedError(getSupportFragmentManager(), ex);
                grpReady.setVisibility(View.VISIBLE);
            }
        }.execute(this, args, "dmarc:decode");
    }

    private static class Loader {
        // https://tools.ietf.org/id/draft-kucherawy-dmarc-base-13.xml#xml_schema
        private DateFormat DTF;
        private int colorWarning;
        private int colorSeparator;
        private float stroke;

        private boolean feedback = false;
        private boolean report_metadata = false;
        private boolean policy_published = false;
        private boolean record = false;
        private boolean row = false;
        private boolean policy_evaluated = false;
        private boolean identifiers = false;
        private boolean auth_results = false;
        private String lastDomain = null;
        private String result = null;
        private List<Pair<String, DnsHelper.DnsRecord>> spf = null;
        private SpannableStringBuilder ssb = new SpannableStringBuilderEx();

        SpannableStringBuilder load(Context context, InputStream is) throws XmlPullParserException, IOException {
            DTF = Helper.getDateTimeInstance(context, DateFormat.SHORT, DateFormat.SHORT);
            colorWarning = Helper.resolveColor(context, R.attr.colorWarning);
            colorSeparator = Helper.resolveColor(context, R.attr.colorSeparator);
            stroke = context.getResources().getDisplayMetrics().density;

            XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
            XmlPullParser xml = factory.newPullParser();
            xml.setInput(is, StandardCharsets.UTF_8.name());

            int eventType = xml.getEventType();
            while (eventType != XmlPullParser.END_DOCUMENT) {
                if (eventType == XmlPullParser.START_TAG) {
                    String name = xml.getName();
                    switch (name) {
                        case "feedback":
                            feedback = true;
                            break;
                        case "report_metadata":
                            report_metadata = true;
                            break;
                        case "policy_published":
                            policy_published = true;
                            lastDomain = null;
                            break;
                        case "record":
                            record = true;
                            break;
                        case "row":
                            row = true;
                            ssb.append("\uFFFC");
                            ssb.setSpan(new LineSpan(colorSeparator, stroke, 0), ssb.length() - 1, ssb.length(), 0);
                            ssb.append("\n");
                            break;
                        case "policy_evaluated":
                            policy_evaluated = true;
                            break;
                        case "identifiers":
                            identifiers = true;
                            break;
                        case "auth_results":
                            auth_results = true;
                            ssb.append("\n");
                            break;

                        case "org_name":
                        case "begin":
                        case "end":
                            if (feedback && report_metadata) {
                                eventType = xml.next();
                                if (eventType == XmlPullParser.TEXT) {
                                    String text = xml.getText();
                                    if (text == null)
                                        text = "<null>";
                                    if ("begin".equals(name) || "end".equals(name)) {
                                        text = text.trim();
                                        try {
                                            ssb.append(name).append('=').append(DTF.format(Long.parseLong(text) * 1000));
                                        } catch (Throwable ex) {
                                            Log.w(ex);
                                            ssb.append(name).append('=').append(text);
                                        }
                                    } else
                                        ssb.append(text);
                                    ssb.append(' ');
                                }
                            }
                            break;
                        case "domain":
                            if (feedback && (policy_published || auth_results)) {
                                eventType = xml.next();
                                if (eventType == XmlPullParser.TEXT) {
                                    String text = xml.getText();
                                    lastDomain = text;
                                    if (text == null)
                                        text = "<null>";
                                    ssb.append(text).append(' ');
                                }
                            }
                            break;
                        case "adkim":
                        case "aspf":
                        case "p":
                        case "sp":
                        case "fo":
                            if (feedback && policy_published) {
                                eventType = xml.next();
                                if (eventType == XmlPullParser.TEXT) {
                                    String text = xml.getText();
                                    if (text == null)
                                        text = "<null>";
                                    if ("adkim".equals(name) || "aspf".equals(name))
                                        if ("r".equals(text))
                                            text = "relaxed";
                                        else if ("s".equals(text))
                                            text = "strict";
                                    ssb.append(name).append('=').append(text).append(' ');
                                }
                            }
                            break;
                        case "pct":
                            if (feedback && policy_published) {
                                eventType = xml.next();
                                if (eventType == XmlPullParser.TEXT) {
                                    String text = xml.getText();
                                    if (text == null)
                                        text = "<null>";
                                    Integer pct = Helper.parseInt(text);
                                    if (pct == null)
                                        ssb.append(name).append('=').append(text).append(' ');
                                    else
                                        ssb.append(text).append("% ");
                                }
                            }

                            break;
                        case "source_ip":
                        case "count":
                            if (feedback && record && row) {
                                eventType = xml.next();
                                if (eventType == XmlPullParser.TEXT) {
                                    String text = xml.getText();
                                    if (text == null)
                                        text = "<null>";
                                    ssb.append(name).append('=').append(text).append(' ');
                                    if ("source_ip".equals(name))
                                        processSourceIp(context, text);
                                }
                            }
                            break;
                        case "disposition": // none, quarantine, reject
                        case "dkim":
                        case "spf":
                        case "header_from":
                        case "envelope_from":
                        case "envelope_to":
                            if (feedback && record)
                                if (policy_evaluated || identifiers) {
                                    eventType = xml.next();
                                    if (eventType == XmlPullParser.TEXT) {
                                        ssb.append(name).append('=');
                                        int start = ssb.length();
                                        String text = xml.getText();
                                        if (text == null)
                                            text = "<null>";
                                        ssb.append(text);

                                        if (!"pass".equals(text.toLowerCase(Locale.ROOT)) &&
                                                ("dkim".equals(name) || "spf".equals(name))) {
                                            ssb.setSpan(new StyleSpan(Typeface.BOLD), start, ssb.length(), 0);
                                            ssb.setSpan(new ForegroundColorSpan(colorWarning), start, ssb.length(), 0);
                                        }

                                        ssb.append(' ');
                                    }
                                } else if (auth_results)
                                    result = name;
                            break;
                        case "result":
                            if (feedback && auth_results) {
                                eventType = xml.next();
                                if (eventType == XmlPullParser.TEXT) {
                                    ssb.append(result == null ? "?" : result).append('=');
                                    int start = ssb.length();
                                    String text = xml.getText();
                                    if (text == null)
                                        text = "<null>";
                                    ssb.append(text);

                                    if (!"pass".equals(text.toLowerCase(Locale.ROOT))) {
                                        ssb.setSpan(new StyleSpan(Typeface.BOLD), start, ssb.length(), 0);
                                        ssb.setSpan(new ForegroundColorSpan(colorWarning), start, ssb.length(), 0);
                                    }

                                    ssb.append(' ');
                                }
                            }
                            break;
                        case "selector":
                        case "scope":
                            if (feedback && auth_results) {
                                eventType = xml.next();
                                if (eventType == XmlPullParser.TEXT) {
                                    String text = xml.getText();
                                    if (text == null)
                                        text = "<null>";
                                    ssb.append(name).append('=').append(text).append(' ');
                                }
                            }
                            break;
                    }

                    if ("report_metadata".equals(name) ||
                            "policy_published".equals(name) ||
                            "row".equals(name) ||
                            "identifiers".equals(name) ||
                            "auth_results".equals(name)) {
                        int start = ssb.length();
                        ssb.append(name);
                        ssb.setSpan(new StyleSpan(Typeface.BOLD), start, ssb.length(), 0);
                        ssb.append("\n");
                    }

                } else if (eventType == XmlPullParser.END_TAG) {
                    String name = xml.getName();
                    switch (name) {
                        case "feedback":
                            feedback = false;
                            break;
                        case "report_metadata":
                            report_metadata = false;
                            if (feedback)
                                ssb.append("\n\n");
                            break;
                        case "policy_published":
                            policy_published = false;
                            if (feedback)
                                ssb.append("\n\n");
                            if (lastDomain == null)
                                spf = null;
                            else
                                processPolicyPublished(context);
                            break;
                        case "record":
                            record = false;
                            break;
                        case "row":
                            row = false;
                            if (feedback)
                                ssb.append("\n\n");
                            break;
                        case "policy_evaluated":
                            policy_evaluated = false;
                            break;
                        case "identifiers":
                            identifiers = false;
                            if (feedback)
                                ssb.append("\n");
                            break;
                        case "auth_results":
                            auth_results = false;
                            if (feedback)
                                ssb.append("\n");
                            break;
                        case "dkim":
                        case "spf":
                            if (feedback && auth_results) {
                                result = null;
                                ssb.append("\n");
                            }
                            break;
                    }
                }

                eventType = xml.next();
            }

            ssb.append("\uFFFC");
            ssb.setSpan(new LineSpan(colorSeparator, stroke, 0), ssb.length() - 1, ssb.length(), 0);
            ssb.append("\n");

            return ssb;
        }

        private void processPolicyPublished(Context context) {
            Integer start = null;
            SpannableStringBuilder extra = new SpannableStringBuilderEx();

            spf = lookupSpf(context, lastDomain, extra);
            for (Pair<String, DnsHelper.DnsRecord> p : spf) {
                ssb.append(p.first).append(' ')
                        .append(p.second.response).append("\n\n");
                if (start == null)
                    start = ssb.length();
            }
            ssb.append(extra);

            if (start != null) {
                ssb.setSpan(new RelativeSizeSpan(HtmlHelper.FONT_SMALL), start, ssb.length(), 0);
                ssb.append("\n");
            }

            List<DnsHelper.DnsRecord> records = new ArrayList<>();
            try {
                records.addAll(Arrays.asList(
                        DnsHelper.lookup(context, "_dmarc." + lastDomain, "txt")));
            } catch (UnknownHostException ignored) {
            }
            try {
                records.addAll(Arrays.asList(
                        DnsHelper.lookup(context, "default._bimi." + lastDomain, "txt")));
            } catch (UnknownHostException ignored) {
            }

            for (DnsHelper.DnsRecord r : records)
                ssb.append(r.response).append("\n");

            ssb.append("\n");
        }

        private void processSourceIp(Context context, String text) {
            try {
                Boolean valid = null;
                String because = null;
                if (spf != null)
                    for (Pair<String, DnsHelper.DnsRecord> p : spf) {
                        for (String ip : p.second.response.split("\\s+")) {
                            boolean allow = true;
                            ip = ip.toLowerCase(Locale.ROOT);
                            if (ip.startsWith("-"))
                                allow = false;
                            else if (ip.startsWith("+"))
                                ip = ip.substring(1);

                            // https://datatracker.ietf.org/doc/html/rfc7208#section-5
                            if (ip.startsWith("ip4:") || ip.startsWith("ip6:")) {
                                String[] net = ip.substring(4).split("/");
                                Integer prefix = (net.length > 1 ? Helper.parseInt(net[1]) : null);
                                if (prefix == null
                                        ? text.equals(net[0])
                                        : ConnectionHelper.inSubnet(text, net[0], prefix)) {
                                    valid = allow;
                                    because = (allow ? '+' : '-') + ip + " in " + p.first;
                                    break;
                                }
                            } else if ("a".equals(ip) || ip.startsWith("a:")) {
                                String domain = (ip.startsWith("a:") ? ip.substring(2) : p.first);
                                String[] net = domain.split("/");
                                Integer prefix = (net.length > 1 ? Helper.parseInt(net[1]) : null);
                                List<DnsHelper.DnsRecord> as = new ArrayList<>();
                                try {
                                    as.addAll(Arrays.asList(DnsHelper.lookup(context, net[0], "a")));
                                } catch (UnknownHostException ignored) {
                                }
                                try {
                                    as.addAll(Arrays.asList(DnsHelper.lookup(context, net[0], "aaaa")));
                                } catch (UnknownHostException ignored) {
                                }
                                for (DnsHelper.DnsRecord a : as)
                                    if (prefix == null
                                            ? text.equals(a.response)
                                            : ConnectionHelper.inSubnet(text, a.response, prefix)) {
                                        valid = allow;
                                        because = (allow ? '+' : '-') + ip +
                                                " in " + domain + (prefix == null ? "" : "/" + prefix);
                                        break;
                                    }
                            } else if ("mx".equals(ip) || ip.startsWith("mx:")) {
                                try {
                                    String domain = (ip.startsWith("mx:") ? ip.substring(3) : p.first);
                                    String[] net = domain.split("/");
                                    Integer prefix = (net.length > 1 ? Helper.parseInt(net[1]) : null);
                                    DnsHelper.DnsRecord[] mxs = DnsHelper.lookup(context, net[0], "mx");
                                    for (DnsHelper.DnsRecord mx : mxs) {
                                        List<DnsHelper.DnsRecord> as = new ArrayList<>();
                                        try {
                                            as.addAll(Arrays.asList(DnsHelper.lookup(context, mx.response, "a")));
                                        } catch (UnknownHostException ignored) {
                                        }
                                        try {
                                            as.addAll(Arrays.asList(DnsHelper.lookup(context, mx.response, "aaaa")));
                                        } catch (UnknownHostException ignored) {
                                        }
                                        for (DnsHelper.DnsRecord a : as) {
                                            if (prefix == null
                                                    ? text.equals(a.response)
                                                    : ConnectionHelper.inSubnet(text, a.response, prefix)) {
                                                valid = allow;
                                                because = (allow ? '+' : '-') + ip +
                                                        " in " + domain + (prefix == null ? "" : "/" + prefix);
                                                break;
                                            }
                                        }
                                        if (valid != null)
                                            break;
                                    }
                                } catch (UnknownHostException ignored) {
                                }
                            } else if ("ptr".equals(ip) || ip.startsWith("ptr:")) {
                                valid = false;
                                because = (allow ? '+' : '-') + ip + " ptr not supported";
                            }
                            if (valid != null)
                                break;
                        }
                        if (valid != null)
                            break;
                    }

                int start = ssb.length();
                ssb.append(Boolean.TRUE.equals(valid) ? "valid" : "invalid");
                if (because != null)
                    ssb.append(" (").append(because).append(')');

                if (!Boolean.TRUE.equals(valid)) {
                    ssb.setSpan(new StyleSpan(Typeface.BOLD), start, ssb.length(), 0);
                    ssb.setSpan(new ForegroundColorSpan(colorWarning), start, ssb.length(), 0);
                }

                ssb.append(' ');
            } catch (Throwable ex) {
                Log.w(ex);
                ssb.append(new ThrowableWrapper(ex).toSafeString()).append('\n');
            }

            try {
                InetAddress addr = InetAddress.getByName(text);
                IPInfo info = IPInfo.getOrganization(addr, context);
                ssb.append('(').append(info.org).append(") ");
            } catch (Throwable ex) {
                Log.w(ex);
                ssb.append(new ThrowableWrapper(ex).toSafeString()).append('\n');
            }
        }

        private static List<Pair<String, DnsHelper.DnsRecord>> lookupSpf(Context context, String domain, SpannableStringBuilder ssb) {
            List<Pair<String, DnsHelper.DnsRecord>> result = new ArrayList<>();

            try {
                DnsHelper.DnsRecord[] records = DnsHelper.lookup(context, domain, "txt:v=spf1 ");
                ssb.append(domain).append('=').append(Integer.toString(records.length)).append('\n');
                for (DnsHelper.DnsRecord r : records) {
                    result.add(new Pair<>(domain, r));
                    for (String part : r.response.split("\\s+"))
                        if (part.toLowerCase(Locale.ROOT).startsWith("include:")) {
                            String sub = part.substring("include:".length());
                            result.addAll(lookupSpf(context, sub, ssb));
                        }
                }
            } catch (Throwable ex) {
                Log.w(ex);
                ssb.append(new ThrowableWrapper(ex).toSafeString()).append('\n');
            }

            return result;
        }
    }
}