using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.Windows.Forms;
using BulkArchiveMailer.Core;
using Outlook = Microsoft.Office.Interop.Outlook;

namespace BulkArchiveMailer.AddIn.UI
{
    /// <summary>
    /// Archive folder, email domain, signature override, test-mode default,
    /// and an arbitrary-length, operator-editable list of mail templates
    /// (master-detail: lstTemplates on the left, editor fields for the
    /// selected one on the right). Saves straight to
    /// %APPDATA%\BulkArchiveMailer\config.json via AppSettings.
    /// </summary>
    public partial class SettingsForm : Form
    {
        private readonly Outlook.Application outlookApplication;

        /// <summary>
        /// In-memory working copy of the template list, edited freely
        /// (add/remove/rename/reorder-by-selection) until btnSave_Click
        /// persists it via AppSettings.Save - nothing here touches disk
        /// until then.
        /// </summary>
        private List<MailTemplateDefinition> templates = new List<MailTemplateDefinition>();

        /// <summary>
        /// Guards against SyncEditorToSelectedTemplate/LoadSelectedTemplateIntoEditor
        /// re-entrancy while lstTemplates.SelectedIndex is being changed
        /// programmatically (as opposed to by the operator clicking in the
        /// list) - the standard pattern for a WinForms master-detail list.
        /// </summary>
        private bool suppressSelectionSync;

        public SettingsForm(Outlook.Application outlookApplication)
        {
            InitializeComponent();
            this.outlookApplication = outlookApplication;
            Load += SettingsForm_Load;
        }

        private void SettingsForm_Load(object sender, EventArgs e)
        {
            AppSettingsData settings;
            try
            {
                settings = AppSettings.Load();
            }
            catch (Exception ex)
            {
                MessageBox.Show(
                    "Не удалось прочитать config.json (" + AppSettings.ConfigFilePath + "):\n" + ex.ToString() +
                    "\n\nБудут показаны пустые настройки — сохранение перезапишет файл заново.",
                    "BulkArchiveMailer",
                    MessageBoxButtons.OK,
                    MessageBoxIcon.Warning);
                settings = new AppSettingsData();
            }

            PopulateFrom(settings);
        }

        /// <summary>ComboBox item: displays a friendly label but carries the SmtpAddress that actually gets saved to config.json. The first item (SmtpAddress == "") represents "let Outlook pick its default account".</summary>
        private sealed class FromAccountItem
        {
            public string Label { get; set; } = "";
            public string SmtpAddress { get; set; } = "";
            public override string ToString() => Label;
        }

        private const string DefaultAccountLabel = "(по умолчанию Outlook)";

        private void PopulateFrom(AppSettingsData settings)
        {
            txtArchiveFolder.Text = settings.ArchiveFolder ?? "";
            txtDomain.Text = settings.EmailDomain ?? "";
            txtSignaturePath.Text = settings.SignatureHtmlPath ?? "";
            chkTestModeDefault.Checked = settings.TestModeDefault;

            PopulateFromAccountCombo(settings.FromAccountSmtpAddress ?? "");

            templates = settings.ToTemplateList();
            PopulateTemplateList(selectFirst: true);
        }

        /// <summary>
        /// Fills cboFromAccount with "(по умолчанию Outlook)" plus one
        /// entry per real Outlook.Account in the current session, then
        /// selects the item matching savedSmtpAddress. If that address no
        /// longer belongs to any account in this session (removed/renamed
        /// since it was configured, or Outlook.Application is unavailable
        /// e.g. under a design-time host), it just falls back to the
        /// default item instead of throwing - never blocks opening the
        /// Settings window over this.
        /// </summary>
        private void PopulateFromAccountCombo(string savedSmtpAddress)
        {
            cboFromAccount.Items.Clear();
            cboFromAccount.Items.Add(new FromAccountItem { Label = DefaultAccountLabel, SmtpAddress = "" });

            if (outlookApplication != null)
            {
                foreach (var account in OutlookAccounts.ListAccounts(outlookApplication))
                {
                    var label = string.IsNullOrEmpty(account.SmtpAddress)
                        ? account.DisplayName
                        : account.DisplayName + " <" + account.SmtpAddress + ">";
                    cboFromAccount.Items.Add(new FromAccountItem { Label = label, SmtpAddress = account.SmtpAddress });
                }
            }

            var selectedIndex = 0;
            if (!string.IsNullOrEmpty(savedSmtpAddress))
            {
                for (var i = 0; i < cboFromAccount.Items.Count; i++)
                {
                    var item = (FromAccountItem)cboFromAccount.Items[i];
                    if (string.Equals(item.SmtpAddress, savedSmtpAddress, StringComparison.OrdinalIgnoreCase))
                    {
                        selectedIndex = i;
                        break;
                    }
                }
            }

            cboFromAccount.SelectedIndex = selectedIndex;
        }

        // --- Template list master-detail -----------------------------------

        /// <summary>Rebuilds lstTemplates' items from the in-memory `templates` list, preserving (or resetting to the first item) the current selection.</summary>
        private void PopulateTemplateList(bool selectFirst)
        {
            suppressSelectionSync = true;
            try
            {
                lstTemplates.Items.Clear();
                foreach (var t in templates)
                {
                    lstTemplates.Items.Add(TemplateListLabel(t));
                }

                if (lstTemplates.Items.Count > 0)
                {
                    lstTemplates.SelectedIndex = selectFirst ? 0 : Math.Min(lstTemplates.Items.Count - 1, lstTemplates.SelectedIndex);
                }
            }
            finally
            {
                suppressSelectionSync = false;
            }

            LoadSelectedTemplateIntoEditor();
        }

        private static string TemplateListLabel(MailTemplateDefinition t) =>
            string.IsNullOrWhiteSpace(t.DisplayName) ? "(без названия)" : t.DisplayName;

        /// <summary>
        /// Rewrites lstTemplates' visible label for the currently-edited
        /// index from the in-memory list (call right after
        /// SyncEditorToSelectedTemplate so the list reflects a renamed
        /// template without a full PopulateTemplateList rebuild, which
        /// would also disturb the current selection/scroll position).
        /// </summary>
        private void RefreshEditedTemplateLabel()
        {
            if (!(lstTemplates.Tag is int editedIndex) || editedIndex < 0 || editedIndex >= templates.Count)
            {
                return;
            }

            suppressSelectionSync = true;
            try
            {
                lstTemplates.Items[editedIndex] = TemplateListLabel(templates[editedIndex]);
            }
            finally
            {
                suppressSelectionSync = false;
            }
        }

        /// <summary>Writes the editor fields' current values back into the in-memory list entry that was selected when editing started (tracked via lstTemplates.Tag, see LoadSelectedTemplateIntoEditor). Safe to call with nothing selected/no prior selection.</summary>
        private void SyncEditorToSelectedTemplate()
        {
            if (!(lstTemplates.Tag is int editedIndex) || editedIndex < 0 || editedIndex >= templates.Count)
            {
                return;
            }

            var t = templates[editedIndex];
            t.DisplayName = txtTplDisplayName.Text;
            t.FileSuffix = txtTplFileSuffix.Text.Trim();
            t.LoginPattern = txtTplLoginPattern.Text.Trim();
            t.Subject = txtTplSubject.Text;
            t.BodyHtml = txtTplBody.Text;
        }

        /// <summary>Loads the newly selected list item's values into the editor fields, and records which index the editor now belongs to (lstTemplates.Tag) so a later SyncEditorToSelectedTemplate knows where to write back.</summary>
        private void LoadSelectedTemplateIntoEditor()
        {
            var index = lstTemplates.SelectedIndex;
            var hasSelection = index >= 0 && index < templates.Count;

            txtTplDisplayName.Enabled = hasSelection;
            txtTplFileSuffix.Enabled = hasSelection;
            txtTplLoginPattern.Enabled = hasSelection;
            txtTplSubject.Enabled = hasSelection;
            txtTplBody.Enabled = hasSelection;

            if (!hasSelection)
            {
                lstTemplates.Tag = -1;
                txtTplDisplayName.Text = "";
                txtTplFileSuffix.Text = "";
                txtTplLoginPattern.Text = "";
                txtTplSubject.Text = "";
                txtTplBody.Text = "";
                return;
            }

            var t = templates[index];
            lstTemplates.Tag = index;
            txtTplDisplayName.Text = t.DisplayName;
            txtTplFileSuffix.Text = t.FileSuffix;
            txtTplLoginPattern.Text = t.LoginPattern;
            txtTplSubject.Text = t.Subject;
            txtTplBody.Text = t.BodyHtml;
        }

        /// <summary>
        /// Keeps lstTemplates' visible label in sync as soon as the
        /// operator finishes editing the name (focus leaves the field),
        /// without waiting for a selection change or Save. Leave (not
        /// TextChanged) deliberately: TextChanged would fire re-entrantly
        /// while LoadSelectedTemplateIntoEditor is itself still in the
        /// middle of setting the other fields for a newly selected
        /// template, which could write stale values back.
        /// </summary>
        private void txtTplDisplayName_Leave(object sender, EventArgs e)
        {
            SyncEditorToSelectedTemplate();
            RefreshEditedTemplateLabel();
        }

        private void lstTemplates_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (suppressSelectionSync)
            {
                return;
            }

            // Save whatever is currently in the editor back to the
            // template it belonged to BEFORE loading the newly selected
            // one - otherwise unsaved edits to the previous selection
            // would be lost the moment the operator clicks another item.
            SyncEditorToSelectedTemplate();
            LoadSelectedTemplateIntoEditor();
        }

        private void btnAddTemplate_Click(object sender, EventArgs e)
        {
            SyncEditorToSelectedTemplate();

            var newTemplate = new MailTemplateDefinition
            {
                DisplayName = "Новый шаблон",
                FileSuffix = "",
                LoginPattern = "",
                Subject = "",
                BodyHtml = "",
            };
            templates.Add(newTemplate);

            PopulateTemplateList(selectFirst: false);
            suppressSelectionSync = true;
            try
            {
                lstTemplates.SelectedIndex = templates.Count - 1;
            }
            finally
            {
                suppressSelectionSync = false;
            }

            LoadSelectedTemplateIntoEditor();
            txtTplDisplayName.Focus();
            txtTplDisplayName.SelectAll();
        }

        private void btnRemoveTemplate_Click(object sender, EventArgs e)
        {
            var index = lstTemplates.SelectedIndex;
            if (index < 0 || index >= templates.Count)
            {
                return;
            }

            var label = TemplateListLabel(templates[index]);
            var confirm = MessageBox.Show(
                this,
                "Удалить шаблон \"" + label + "\"? Несохранённые правки в этом окне будут потеряны только после нажатия \"Сохранить\".",
                "Подтверждение",
                MessageBoxButtons.YesNo,
                MessageBoxIcon.Question);
            if (confirm != DialogResult.Yes)
            {
                return;
            }

            templates.RemoveAt(index);

            // The editor currently holds this now-removed template's stale
            // values - clear its "which index does the editor belong to"
            // marker so a later SyncEditorToSelectedTemplate (e.g. from the
            // SelectedIndexChanged this RemoveAt is about to trigger) does
            // not write those stale values into whatever template happens
            // to occupy this index next.
            lstTemplates.Tag = -1;

            var nextIndex = templates.Count == 0 ? -1 : Math.Min(index, templates.Count - 1);
            suppressSelectionSync = true;
            try
            {
                lstTemplates.Items.RemoveAt(index);
                lstTemplates.SelectedIndex = nextIndex;
            }
            finally
            {
                suppressSelectionSync = false;
            }

            LoadSelectedTemplateIntoEditor();
        }

        // --- General tab handlers --------------------------------------

        private void btnBrowseFolder_Click(object sender, EventArgs e)
        {
            using (var dialog = new FolderBrowserDialog())
            {
                dialog.Description = "Папка с архивами, которые ssh-access-tui выкладывает для рассылки";
                if (System.IO.Directory.Exists(txtArchiveFolder.Text))
                {
                    dialog.SelectedPath = txtArchiveFolder.Text;
                }

                if (dialog.ShowDialog(this) == DialogResult.OK)
                {
                    txtArchiveFolder.Text = dialog.SelectedPath;
                }
            }
        }

        private void btnBrowseSignature_Click(object sender, EventArgs e)
        {
            using (var dialog = new OpenFileDialog())
            {
                dialog.Title = "Выберите файл подписи";
                dialog.Filter = "HTML-подпись (*.htm;*.html)|*.htm;*.html|Все файлы (*.*)|*.*";
                if (dialog.ShowDialog(this) == DialogResult.OK)
                {
                    txtSignaturePath.Text = dialog.FileName;
                }
            }
        }

        private void btnAutoDetectSignature_Click(object sender, EventArgs e)
        {
            if (outlookApplication == null)
            {
                MessageBox.Show(this, "Outlook.Application недоступен в этом окне.", "BulkArchiveMailer", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                return;
            }

            var path = SignatureReader.TryAutoDetectSignaturePath(outlookApplication);
            if (string.IsNullOrEmpty(path))
            {
                MessageBox.Show(
                    this,
                    "Не удалось определить подпись автоматически (не настроена подпись по умолчанию для новых писем, либо файл не найден). Выберите файл вручную кнопкой \"Обзор...\".",
                    "BulkArchiveMailer",
                    MessageBoxButtons.OK,
                    MessageBoxIcon.Information);
                return;
            }

            txtSignaturePath.Text = path;
        }

        private void btnResetDefaults_Click(object sender, EventArgs e)
        {
            var confirm = MessageBox.Show(
                this,
                "Заменить домен и весь список шаблонов писем значениями по умолчанию (два исходных шаблона)? Папка с архивами и файл подписи не изменятся. Несохранённые правки в этом окне будут потеряны.",
                "Подтверждение",
                MessageBoxButtons.YesNo,
                MessageBoxIcon.Question);
            if (confirm != DialogResult.Yes)
            {
                return;
            }

            var defaults = AppSettings.LoadDefaults();
            txtDomain.Text = defaults.EmailDomain;

            templates = defaults.ToTemplateList();
            PopulateTemplateList(selectFirst: true);
        }

        private void btnSave_Click(object sender, EventArgs e)
        {
            if (string.IsNullOrWhiteSpace(txtDomain.Text))
            {
                MessageBox.Show(this, "Домен электронной почты не может быть пустым.", "BulkArchiveMailer", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                tabControl.SelectedTab = tabGeneral;
                txtDomain.Focus();
                return;
            }

            if (!string.IsNullOrWhiteSpace(txtArchiveFolder.Text) && !System.IO.Directory.Exists(txtArchiveFolder.Text))
            {
                var proceed = MessageBox.Show(
                    this,
                    "Указанная папка с архивами не существует:\n" + txtArchiveFolder.Text + "\n\nВсё равно сохранить?",
                    "BulkArchiveMailer",
                    MessageBoxButtons.YesNo,
                    MessageBoxIcon.Warning);
                if (proceed != DialogResult.Yes)
                {
                    tabControl.SelectedTab = tabGeneral;
                    return;
                }
            }

            // Make sure whatever is currently in the editor (possibly never
            // committed by a selection change, e.g. the operator edited one
            // template and clicked Save directly) is captured before
            // validating/saving the list.
            SyncEditorToSelectedTemplate();

            var suffixError = ValidateTemplateSuffixes();
            if (suffixError != null)
            {
                MessageBox.Show(this, suffixError, "BulkArchiveMailer", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                tabControl.SelectedTab = tabTemplates;
                lstTemplates.Focus();
                return;
            }

            var loginPatternError = ValidateTemplateLoginPatterns();
            if (loginPatternError != null)
            {
                MessageBox.Show(this, loginPatternError, "BulkArchiveMailer", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                tabControl.SelectedTab = tabTemplates;
                lstTemplates.Focus();
                return;
            }

            var selectedAccount = cboFromAccount.SelectedItem as FromAccountItem;

            var data = new AppSettingsData
            {
                ArchiveFolder = txtArchiveFolder.Text.Trim(),
                EmailDomain = txtDomain.Text.Trim(),
                SignatureHtmlPath = txtSignaturePath.Text.Trim(),
                TestModeDefault = chkTestModeDefault.Checked,
                FromAccountSmtpAddress = selectedAccount?.SmtpAddress ?? "",
            };
            data.SetTemplates(templates);

            try
            {
                AppSettings.Save(data);
            }
            catch (Exception ex)
            {
                MessageBox.Show(this, "Не удалось сохранить настройки: " + ex.ToString(), "BulkArchiveMailer", MessageBoxButtons.OK, MessageBoxIcon.Error);
                return;
            }

            DialogResult = DialogResult.OK;
            Close();
        }

        /// <summary>
        /// Every template's FileSuffix must be non-empty, and unique
        /// case-insensitively among all configured templates (it is
        /// ArchiveScanner's only way to match a file to a template).
        /// Returns null if valid, otherwise a message describing exactly
        /// which template/duplicate is the problem.
        /// </summary>
        private string ValidateTemplateSuffixes()
        {
            for (var i = 0; i < templates.Count; i++)
            {
                if (string.IsNullOrWhiteSpace(templates[i].FileSuffix))
                {
                    var name = string.IsNullOrWhiteSpace(templates[i].DisplayName) ? $"#{i + 1}" : templates[i].DisplayName;
                    return $"У шаблона \"{name}\" не заполнен суффикс файла — заполните поле \"Суффикс файла\" (например, \"ssh_access\").";
                }
            }

            var duplicateGroup = templates
                .GroupBy(t => t.FileSuffix.Trim(), StringComparer.OrdinalIgnoreCase)
                .FirstOrDefault(g => g.Count() > 1);
            if (duplicateGroup != null)
            {
                var names = string.Join(", ", duplicateGroup.Select(t => string.IsNullOrWhiteSpace(t.DisplayName) ? "(без названия)" : t.DisplayName));
                return $"Суффикс файла \"{duplicateGroup.Key}\" используется в нескольких шаблонах ({names}) — суффикс должен быть уникальным.";
            }

            return null;
        }

        /// <summary>
        /// Every template's LoginPattern (if non-empty) must compile as a
        /// .NET regular expression - ArchiveScanner treats an uncompilable
        /// pattern defensively as "never matches" rather than throwing, but
        /// that would silently turn a typo'd filter into "this template
        /// never applies to anything", which is worth catching here instead
        /// while the operator still has the exact field in front of them.
        /// Returns null if every configured pattern is either empty or
        /// compiles, otherwise a message naming the offending template and
        /// the underlying regex error.
        /// </summary>
        private string ValidateTemplateLoginPatterns()
        {
            for (var i = 0; i < templates.Count; i++)
            {
                var pattern = templates[i].LoginPattern;
                if (string.IsNullOrEmpty(pattern))
                {
                    continue;
                }

                try
                {
                    _ = new Regex(pattern);
                }
                catch (ArgumentException ex)
                {
                    var name = string.IsNullOrWhiteSpace(templates[i].DisplayName) ? $"#{i + 1}" : templates[i].DisplayName;
                    return $"У шаблона \"{name}\" некорректное регулярное выражение в поле \"Фильтр логина\" (\"{pattern}\"): {ex.Message}";
                }
            }

            return null;
        }

        private void btnCancel_Click(object sender, EventArgs e)
        {
            DialogResult = DialogResult.Cancel;
            Close();
        }
    }
}