using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Controls;
using Elwig.Models;

namespace Elwig.Helpers {
    public static class Validator {

        private static readonly Dictionary<string, string[][]> PHONE_NRS = new() {
            { "43", new string[][] {
                Array.Empty<string>(),
                new string[] { "57", "59" },
                new string[] {
                    "50", "517", "718", "804", "720", "780", "800", "802", "810",
                    "820", "821", "828", "900", "901", "930", "931", "939",
                    "650", "651", "652", "653", "655", "657", "659", "660", "661",
                    "663", "664", "665", "666", "667", "668", "669", "67", "68", "69"
                }
            } },
            { "49", Array.Empty<string[]>() },
            { "48", Array.Empty<string[]>() },
            { "420", Array.Empty<string[]>() },
            { "421", Array.Empty<string[]>() },
            { "36", Array.Empty<string[]>() },
            { "386", Array.Empty<string[]>() },
            { "39", Array.Empty<string[]>() },
            { "33", Array.Empty<string[]>() },
            { "41", Array.Empty<string[]>() },
            { "423", Array.Empty<string[]>() },
        };

        public static ValidationResult CheckInteger(TextBox input, bool required) {
            return CheckInteger(input, required, -1);
        }

        public static ValidationResult CheckInteger(TextBox input, bool required, int maxLen) {
            string text = "";
            int pos = input.CaretIndex;
            for (int i = 0; i < input.Text.Length; i++) {
                char ch = input.Text[i];
                if (char.IsAsciiDigit(ch))
                    text += ch;
                if (i == input.CaretIndex - 1)
                    pos = text.Length;
            }
            input.Text = text;
            input.CaretIndex = pos;

            if (text.Length == 0) {
                return required ? new(false, "Wert ist nicht optional") : new(true, null);
            }

            if (maxLen >= 0 && input.Text.Length > maxLen) {
                input.Text = input.Text[..maxLen];
                input.CaretIndex = Math.Min(pos, maxLen);
            }

            return new(true, null);
        }

        public static ValidationResult CheckPlz(TextBox input, bool required, AppDbContext ctx) {
            CheckInteger(input, false, 4);
            if (!required && input.Text.Length == 0) {
                return new(true, null);
            } else if (input.Text.Length != 4) {
                return new(false, "PLZ zu kurz");
            }
            int plz = int.Parse(input.Text);
            if (ctx.Postleitzahlen.Find(plz) == null) {
                return new(false, "Ungültige PLZ");
            }
            return new(true, null);
        }

        public static ValidationResult CheckPhoneNumber(TextBox input, bool required) {
            string text = "";
            int pos = input.CaretIndex;
            for (int i = 0, v = 0; i < input.Text.Length && v < 15; i++) {
                char ch = input.Text[i];
                if (v == 0 && input.Text.Length - i >= 2 && ch == '0' && input.Text[i + 1] == '0') {
                    v++; i++;
                    text += '+';
                } else if (ch == '(' && input.Text.Length - i >= 3 && input.Text[i + 1] == '0' && input.Text[i + 2] == ')') {
                    i += 2;
                } else if (v == 0 && ch == '0') {
                    v += 3;
                    text += "+43";
                } else if (v == 0 && ch == '+') {
                    v++;
                    text += ch;
                } else if (v > 0 && char.IsAsciiDigit(ch)) {
                    if (PHONE_NRS.Any(kv => text == "+" + kv.Key))
                        text += ' ';
                    if (text.StartsWith("+43 ")) {
                        var nr = text[4..];
                        var vws = PHONE_NRS["43"];
                        if (v >= 4 && v - 4 < vws.Length && vws[v - 4].Any(vw => nr.StartsWith(vw)))
                            text += ' ';
                        else if (nr == "1")
                            text += ' ';
                        else if (v == 7 && nr.Length == 4)
                            text += ' ';
                    }
                    v++;
                    text += ch;
                }
                if (i == input.CaretIndex - 1)
                    pos = text.Length;
            }
            input.Text = text;
            input.CaretIndex = pos;

            if (!required && text.Length == 0) {
                return new(true, null);
            } else if (text.Length < 10) {
                return new(false, "Telefonnummer zu kurz");
            }

            return new(true, null);
        }

        public static ValidationResult CheckEmailAddress(TextBox input, bool required) {
            string text = "";
            int pos = input.CaretIndex;
            bool domain = false;
            for (int i = 0; i < input.Text.Length && text.Length < 256; i++) {
                char ch = input.Text[i];
                if (domain) {
                    if ((char.IsAsciiLetterOrDigit(ch)) || ".-_öäüßÖÄÜẞ".Any(c => c == ch)) {
                        if (!(text.Last() == '.' && ch == '.'))
                            text += char.ToLower(ch);
                    }
                } else {
                    if (ch == '@')
                        domain = true;
                    if (!char.IsControl(ch) && !char.IsWhiteSpace(ch))
                        text += ch;
                }

                if (i == input.CaretIndex - 1)
                    pos = text.Length;
            }
            input.Text = text;
            input.CaretIndex = pos;

            if (text.Length == 0) {
                return required ? new(false, "E-Mail-Adresse ist nicht optional") : new(true, null);
            } else if (text[0] == '@' || !domain) {
                return new(false, "E-Mail-Adresse ungültig");
            }

            var last = text.Split(".").Last();
            if (last.Length < 2 || !last.All(ch => char.IsAsciiLetterLower(ch)))
                return new(false, "E-Mail-Adresse ungültig");

            return new(true, null);
        }

        public static ValidationResult CheckIban(TextBox input, bool required) {
            string text = "";
            int pos = input.CaretIndex;
            int v = 0;
            for (int i = 0; i < input.Text.Length && v < 34; i++) {
                char ch = input.Text[i];
                if (char.IsAsciiLetterOrDigit(ch)) {
                    if (((v < 2 && char.IsAsciiLetter(ch)) || (v >= 2 && v < 4 && char.IsAsciiDigit(ch)) || v >= 4) &&
                        ((!text.StartsWith("AT") && !text.StartsWith("DE")) || char.IsAsciiDigit(ch)))
                    {
                        if (v != 0 && v % 4 == 0)
                            text += ' ';
                        v++;
                        text += char.ToUpper(ch);
                    }
                }
                if (i == input.CaretIndex - 1)
                    pos = text.Length;
                if (text.StartsWith("AT") && v >= 20)
                    break;
                else if (text.StartsWith("DE") && v >= 22)
                    break;
            }
            input.Text = text;
            input.CaretIndex = pos;

            if (!required && text.Length == 0) {
                return new(true, null);
            } else if (v < 5 || (text.StartsWith("AT") && v != 20) || (text.StartsWith("DE") && v != 22)) {
                return new(false, "IBAN hat falsche Länge");
            }

            var validation = (text[4..] + text[..4]).Replace(" ", "")
                .Select(ch => char.IsAsciiDigit(ch) ? ch.ToString() : (ch - 'A' + 10).ToString())
                .Aggregate((a, b) => a + b);
            if (Utils.Modulo(validation, 97) != 1)
                return new(false, "Prüfsumme der IBAN ist falsch");

            return new(true, null);
        }

        public static ValidationResult CheckBic(TextBox input, bool required) {
            string text = "";
            int pos = input.CaretIndex;
            for (int i = 0, v = 0; i < input.Text.Length; i++) {
                char ch = input.Text[i];
                if ((v < 4 || v >= 6) && char.IsAsciiLetterOrDigit(ch)) {
                    v++;
                    text += char.ToUpper(ch);
                } else if (v >= 4 && v < 6 && char.IsAsciiLetter(ch)) {
                    v++;
                    text += char.ToUpper(ch);
                }

                if (i == input.CaretIndex - 1)
                    pos = text.Length;
            }

            if (text.Length == 0) {
                return required ? new(false, "BIC ist nicht optional") : new(true, null);
            }

            if (text.Length > 11) {
                text = text[..11];
                pos = Math.Min(pos, 11);
            }

            if (text.Length == 11 && text.EndsWith("XXX"))
                text = text[..8];

            input.Text = text;
            input.CaretIndex = pos;

            if (text.Length != 11 && text.Length != 8)
                return new(false, "BIC ist ungültig");

            return new(true, null);
        }

        public static ValidationResult CheckLfbisNr(TextBox input, bool required) {
            var res = CheckInteger(input, false, 7);
            if (!res.IsValid) {
                return res;
            } else if (!required && input.Text.Length == 0) {
                return new(true, null);
            } else if (input.Text.Length != 7) {
                return new(false, "Betriebsnummer zu kurz");
            }

            // https://statistik.at/fileadmin/shared/QM/Standarddokumentationen/RW/std_r_land-forstw_register.pdf#page=41
            int s = 0, v;
            for (int i = 0; i < 6; i++)
                s += (input.Text[i] - '0') * (7 - i);
            v = (11 - (s % 11)) % 10;

            if (v != (input.Text[6] - '0'))
                return new(false, "Prüfsumme der Betriebsnummer ist falsch");

            return new(true, null);
        }

        public static ValidationResult CheckUstId(TextBox input, bool required) {
            string text = "";
            int pos = input.CaretIndex;
            for (int i = 0, v = 0; i < input.Text.Length; i++) {
                char ch = input.Text[i];
                if (v < 2 && char.IsAsciiLetter(ch)) {
                    v++;
                    text += char.ToUpper(ch);
                } else if (v >= 2 && char.IsAsciiLetterOrDigit(ch)) {
                    if (text.StartsWith("AT")) {
                        if (v == 2 && (ch == 'u' || ch == 'U')) {
                            v++;
                            text += 'U';
                        } else if (v > 2 && char.IsAsciiDigit(ch)) {
                            v++;
                            text += ch;
                        }
                    } else {
                        v++;
                        text += char.ToUpper(ch);
                    }
                }

                if (i == input.CaretIndex - 1) {
                    pos = text.Length;
                } else if (v >= 14) {
                    break;
                } else if (text.StartsWith("AT") && v >= 11) {
                    break;
                }
            }

            input.Text = text;
            input.CaretIndex = pos;

            if (text.Length == 0)
                return required ? new(false, "UID ist nicht optional") : new(true, null);

            if (text.StartsWith("AT")) {
                if (text.Length != 11 || text[2] != 'U')
                    return new(false, "UID ist ungültig");

                // http://www.pruefziffernberechnung.de/U/USt-IdNr.shtml
                int s = 0, v = 0;
                for (int i = 0; i < 7; i++)
                    s += ((text[i + 3] - '0') * (i % 2 + 1)).ToString().Select(ch => ch - '0').Sum();
                v = (96 - s) % 10;

                if (v != (text[10] - '0'))
                    return new(false, "Prüfsumme der UID ist falsch");
            } else {
                return new(false, "Not implemented yet");
            }

            return new(true, null);
        }

        public static ValidationResult CheckMgNr(TextBox input, bool required, AppDbContext ctx, Member? m) {
            var res = CheckInteger(input, required);
            if (!res.IsValid) {
                return res;
            } else if (!required && input.Text.Length == 0) {
                return new(true, null);
            }

            int nr = int.Parse(input.Text);
            if (nr != m?.MgNr && ctx.MgNrExists(nr).GetAwaiter().GetResult()) {
                return new(false, "Mitgliedsnummer wird bereits verwendet");
            }

            return new(true, null);
        }

        public static ValidationResult CheckPredecessorMgNr(TextBox input, bool required, AppDbContext ctx) {
            var res = CheckInteger(input, required);
            if (!res.IsValid) {
                return res;
            } else if (!required && input.Text.Length == 0) {
                return new(true, null);
            } else if (!ctx.MgNrExists(int.Parse(input.Text)).GetAwaiter().GetResult()) {
                return new(false, "Ein Mitglied mit dieser Mitgliedsnummer existiert nicht");
            }

            return new(true, null);
        }

        public static ValidationResult CheckDate(TextBox input, bool required) {
            return CheckDate(input, required, false);
        }

        public static ValidationResult CheckPartialDate(TextBox input, bool required) {
            return CheckDate(input, required, true);
        }

        private static ValidationResult CheckDate(TextBox input, bool required, bool partial) {
            string text = "";
            int pos = input.CaretIndex;
            int p = 0;
            var parts = new string?[3];
            parts[0] = "";
            for (int i = 0; i < input.Text.Length; i++) {
                char ch = input.Text[i];
                if (ch == '.') {
                    if (p < 2 && (parts[p]?.Length > 0 || pos == text.Length)) {
                        if (parts[p]?.Length == 1 && ((pos != text.Length && pos != text.Length - 1) || !input.IsFocused)) {
                            parts[p] = "0" + parts[p];
                            text = text[..(text.Length - 1)] + "0" + text[^1];
                        }
                        parts[++p] = "";
                        text += '.';
                    }
                } else if (char.IsAsciiDigit(ch)) {
                    if ((partial && parts[p]?.Length < 4) || (!partial && ((p < 2 && parts[p]?.Length < 2) || (p == 2 && parts[2]?.Length < 4)))) {
                        parts[p] += ch;
                        text += ch;
                    }
                    if (p == 0 && pos == 1 && input.Text.Length >= 4 && input.Text.Length <= 9) {
                        parts[++p] = "";
                        text += '.';
                        continue;  // skip caret update
                    }
                }

                if (i == input.CaretIndex - 1) {
                    pos = text.Length;
                }
            }

            input.Text = text;
            input.CaretIndex = pos;

            if (text.Length == 0)
                return required ? new(false, "Datum ist nicht optional") : new(true, null);

            if (partial) {
                if (p == 0) {
                    // only year provided
                    return (parts[0]?.Length == 4) ? new(true, null) : new(false, "Datum ist ungültig");
                } else if (p == 1) {
                    // only month and year provided
                    int m = parts[0] != null && parts[0] != "" ? int.Parse(parts[0] ?? "0") : 0;
                    if (parts[1]?.Length != 4 || parts[0]?.Length != 2 || m < 1 || m > 12)
                        return new(false, "Datum ist ungültig");
                    return new(true, null);
                }
            }

            if (!DateOnly.TryParseExact(text, "dd.MM.yyyy", out _))
                return new(false, "Datum ist ungültig");

            return new(true, null);
        }

        public static ValidationResult CheckFbNr(TextBox input, bool required, AppDbContext ctx, AreaCom? c) {
            var res = CheckInteger(input, required);
            if (!res.IsValid) {
                return res;
            } else if (!required && input.Text.Length == 0) {
                return new(true, null);
            }

            int nr = int.Parse(input.Text);
            if (nr != c?.FbNr && ctx.FbNrExists(nr).GetAwaiter().GetResult()) {
                return new(false, "Flächenbindungsnummer wird bereits verwendet");
            }

            return new(true, null);
        }

        public static ValidationResult CheckGstNr(TextBox input, bool required) {
            // TODO
            return new(true, "Not implemented yet");
        }
    }
}