using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Text.RegularExpressions;
using Discord;
using Discord.WebSocket;
using Microsoft.EntityFrameworkCore;
using PagerParser.Handlers;

namespace PagerParser {
    public partial class PagerContext {
        public DbSet<DiscordAlertChannel>      DiscordAlertChannels      { get; set; }
        public DbSet<DiscordAlertSubscription> DiscordAlertSubscriptions { get; set; }
    }
}

namespace PagerParser.Handlers {
    [PagerHandler]
    internal class DiscordHandler : IPagerHandler {
        // TODO: consolidate this with the map used by TTS
        private readonly Dictionary<string, string> IncidentTypes = new() {
            { "ALAR", "FIRE ALARM"        },
            { "G&S",  "GRASS & SCRUB"     },
            { "HIAR", "HIGH-ANGLE RESCUE" },
            { "INCI", "INCIDENT"          },
            { "NOST", "NON-STRUCTURE"     },
            { "RESC", "RESCUE"            },
            { "STRU", "STRUCTURE"         }
        };

        private readonly CommandBuilder[] CommandBuilders;

        private DiscordSocketClient discordClient;

        private Dictionary<int, DateTime> recentMessages = new();

        private string botToken;

        private ILogger          logger;
        private IServiceProvider serviceProvider;

        public DiscordHandler() {
            // Initialize the command builders here so that instance
            // methods may be used for command handling.
            CommandBuilders = [
                new CommandBuilder() {
                    Name           = "get-channel",
                    Description    = "Get the channel to which alerts will be sent",
                    ContextTypes   = [ InteractionContextType.Guild ],
                    CommandHandler = OnGetChannelCommand,
                },
                new CommandBuilder() {
                    Name           = "set-channel",
                    Description    = "Set the channel to which alerts will be sent",
                    ContextTypes   = [ InteractionContextType.Guild ],
                    CommandHandler = OnSetChannelCommand,
                    Options        = [
                        new() {
                            Name        = "channel",
                            Description = "Channel to which alerts will be sent",
                            Type        = ApplicationCommandOptionType.Channel,
                            IsRequired  = true
                        },
                        new() {
                            Name        = "all-messages",
                            Description = "Send messages even if nobody is subcribed (defaults to 'False')",
                            Type        = ApplicationCommandOptionType.Boolean,
                        }
                    ]
                },
                new CommandBuilder() {
                    Name           = "remove-channel",
                    Description    = "Reset the configured alert channel, effectively disabling alerts for this server",
                    CommandHandler = OnRemoveChannelCommand
                },
                new CommandBuilder() {
                    Name           = "subscribe",
                    Description    = "Subscribe a user/role to alerts for the specified brigade/appliance",
                    ContextTypes   = [ InteractionContextType.Guild ],
                    CommandHandler = OnSubscribeChannelCommand,
                    Options        = [
                        new() {
                            Name        = "mention",
                            Description = "User/role to subscribe",
                            Type        = ApplicationCommandOptionType.Mentionable,
                            IsRequired  = true
                        },
                        new() {
                            Name        = "brigade",
                            Description = "Paged brigade/appliance to match (e.g. BERW, FS88, etc)",
                            Type        = ApplicationCommandOptionType.String,
                            IsRequired  = true
                        }
                    ]
                },
                new CommandBuilder() {
                    Name           = "unsubscribe",
                    Description    = "Unsubscribe a user/role from alerts for the specified brigade/appliance",
                    ContextTypes   = [ InteractionContextType.Guild ],
                    CommandHandler = OnUnsubscribeChannelCommand,
                    Options        = [
                        new() {
                            Name        = "mention",
                            Description = "User/role to unsubscribe",
                            Type        = ApplicationCommandOptionType.Mentionable,
                            IsRequired  = true
                        },
                        new() {
                            Name        = "brigade",
                            Description = "Paged brigade/appliance to match (e.g. BERW, FS88, etc)",
                            Type        = ApplicationCommandOptionType.String,
                            IsRequired  = true
                        }
                    ]
                },
                new CommandBuilder() {
                    Name           = "list-subscriptions",
                    Description    = "List the brigades/appliances whose pager messages the user/role is subscribed to",
                    ContextTypes   = [ InteractionContextType.Guild ],
                    CommandHandler = OnListSubscriptionsCommand,
                    Options        = [
                        new() {
                            Name        = "mention",
                            Description = "User/role whose subscriptions will be listed (defaults to the current user)",
                            Type        = ApplicationCommandOptionType.Mentionable
                        }
                    ]
                }
            ];
        }

        public async Task HandleMessageAsync(PagerMessage message, ParsedPagerMessage? pm) {
            if(pm is null)
                return;

            // Calculate a hash to eliminate duplicate messages
            var hash = (
                pm.AssignmentArea,
                pm.JobType,
                pm.AlertLevel,
                pm.Description,
                pm.FireGroundChannel,
                pm.FirecomJobNo).GetHashCode();

            // Prune the hash list
            recentMessages
                .Where(kv => DateTime.Now - kv.Value > TimeSpan.FromMinutes(2))
                .Select(kv => kv.Key)
                .ToList()
                .ForEach(h => recentMessages.Remove(h));

            // Ignore this message if we've seen a similar one recently
            if(recentMessages.Keys.Contains(hash))
                return;

            // Record the hash of this message for future deduplication
            recentMessages[hash] = DateTime.Now;

            // Get a simplified list of paged services
            var pagedServices = pm.PagedServices
                .Select(ps => Regex.Replace(ps, "^C([A-Z]{4})$", "$1"))
                .Select(ps => Regex.Replace(ps, "^[A-Z]*([0-9]{2})[A-Z]*", "FS$1"))
                .Order()
                .Distinct();

            // Translate the job type to a more friendly string
            string mapType = PagerMessageParserService.MapTypeMap
                .FirstOrDefault(kv => kv.Value == pm.MapType).Key;
            IncidentTypes.TryGetValue(pm.JobType, out var incidentType);

            // Compose a base message to be posted to each configured webhook
            string[] messageComponents = [
                Color(AnsiColor.Red, "ALERT"),
                Color(pm.AlertLevel == AlertLevel.Code1 ? AnsiColor.Red : AnsiColor.White, $"CODE {(int) pm.AlertLevel}"),
                pm.AssignmentArea,
                Color(AnsiColor.Cyan, incidentType ?? pm.JobType),
                pm.Description,
                Color(AnsiColor.Blue, $"{mapType} {pm.MapNo} {pm.MapGrid} ({pm.GridReference})"),
                Color(AnsiColor.Cyan, pm.Note ?? ""),
                pm.FireGroundChannel is null ? "" : Color(AnsiColor.Yellow, $"FGD{pm.FireGroundChannel}"),
                Color(AnsiColor.Magenta, $"F{pm.FirecomJobNo}")
            ];

            string baseMessage =
                $"```ansi\n{string.Join(' ', messageComponents.Where(x => !string.IsNullOrEmpty(x)))}\n```";

            using var scope = serviceProvider.CreateScope();
            using var db    = scope.ServiceProvider.GetRequiredService<PagerContext>();

            foreach(var guild in discordClient.Guilds) {
                // Check that a notification channel is assigned for this guild,
                // otherwise, skip it.
                var alertChannel = db.DiscordAlertChannels
                    .Where(ac => ac.GuildId == guild.Id)
                    .FirstOrDefault();
                if(alertChannel is null)
                    continue;

                // Get a list of alert groups matching the page we've just received
                var subscriptions = db.DiscordAlertSubscriptions
                    .Where(s => s.GuildId == guild.Id)
                    .Where(s => pagedServices.Contains(s.PageDestination))
                    .ToArray();

                // Don't post the message to the server if nobody has subscribed
                // and this alert channel is configured for alerts to only be
                // posted when they mention a specific user or role.
                if(subscriptions.Count() == 0 && alertChannel.RequireMention)
                    continue;

                // Figure out which roles and users we need to @ mention
                // and generate appropriate Discord mention strings
                var roleMentions = subscriptions
                    .Where(s => s.PrincipalType == DiscordPrincipalType.Role)
                    .Distinct()
                    .Select(s => MentionUtils.MentionRole(s.PrincipalId));

                var userMentions = subscriptions
                    .Where(s => s.PrincipalType == DiscordPrincipalType.User)
                    .Distinct()
                    .Select(s => MentionUtils.MentionUser(s.PrincipalId));

                var mentions = string.Join(' ', roleMentions.Concat(userMentions));

                // Generate a list of paged services to be highlighted.
                // Services are highlighted if they exist in one of the
                // pre-configured alert groups and have therefore caused
                // a role to be mentioned.
                var hl = subscriptions
                    .Select(s => s.PageDestination)
                    .Distinct()
                    .ToArray();

                // Cleanup the list of paged services and generate
                // text to be displayed
                var pagedServicesText = string.Join(' ', pagedServices
                    .Select(ps => hl.Contains(ps) ? $"***{ps}***" : $"*{ps}*"));

                // Generate a message tailored to the
                // specific webhook we're posting to
                string discordMessage =
                    $"{(string.IsNullOrEmpty(mentions) ? "" : mentions + '\n')}" +
                    baseMessage +
                    $"\nPaged Services: {pagedServicesText}";

                // Actually post the message
                try {
                    await guild
                        .GetTextChannel(alertChannel.ChannelId)
                        .SendMessageAsync(discordMessage);
                } catch(Exception e) {
                    logger.LogError(
                        e,
                        "Error sending Discord message");
                }
            }
        }

        private async Task OnGetChannelCommand(SocketSlashCommand command) {
            using var scope = serviceProvider.CreateScope();
            using var db    = scope.ServiceProvider.GetRequiredService<PagerContext>();

            var alertChannel = db.DiscordAlertChannels
                .FirstOrDefault(c => c.GuildId == command.GuildId);

            if(alertChannel is null) {
                await command.RespondAsync(
                    ephemeral: true,
                    text:      "No alert channel has been configured for this server!");
                return;
            }

            await command.RespondAsync(
                ephemeral: true,
                text: string.Join(' ', [
                    $"The configured alert channel for this server is",
                    $"<#{alertChannel.ChannelId}>",
                    alertChannel.RequireMention ? null : "(all messages will be sent)"
                ]));
        }

        private async Task OnSetChannelCommand(SocketSlashCommand command) {
            logger.LogDebug("Executing the 'set-channel' command...");

            using var scope = serviceProvider.CreateScope();
            using var db    = scope.ServiceProvider.GetRequiredService<PagerContext>();

            await db.Database.BeginTransactionAsync();

            var alertChannel = await db.DiscordAlertChannels
                .FirstOrDefaultAsync(c => c.GuildId == command.GuildId);

            // Ensure the selected channel is actually a
            // text channel and not a channel category.
            if(command.Data.Options.First().Value is not SocketTextChannel) {
                await command.RespondAsync(
                    ephemeral: true,
                    text:      "Error: Pager message notifications can only be posted to text channels");
                return;
            }

            var channel = (SocketTextChannel) command.Data.Options.First().Value;
            var requireMention = !command.Data.Options
                .Where(o => o.Type == ApplicationCommandOptionType.Boolean)
                .Select(o => (bool?) o.Value)
                .FirstOrDefault() ?? true;

            if(alertChannel is null) {
                alertChannel = new() {
                    GuildId        = (ulong) command.GuildId!,
                    ChannelId      = channel.Id,
                    RequireMention = requireMention
                };
                await db.DiscordAlertChannels.AddAsync(alertChannel);
            } else {
                alertChannel.ChannelId      = channel.Id;
                alertChannel.RequireMention = requireMention;
            }

            await db.SaveChangesAsync();
            await db.Database.CommitTransactionAsync();

            await command.RespondAsync(
                ephemeral: true,
                text: string.Join(' ', [
                    "The alert channel for this server has been set to",
                    $"<#{channel.Id}>",
                    requireMention ? null : "(all messages will be sent)"
                ]));
        }

        private async Task OnRemoveChannelCommand(SocketSlashCommand command) {
            using var scope = serviceProvider.CreateScope();
            using var db    = scope.ServiceProvider.GetRequiredService<PagerContext>();

            await db.Database.BeginTransactionAsync();

            var alertChannel = await db.DiscordAlertChannels
                .FirstOrDefaultAsync(c => c.GuildId == command.GuildId);

            if(alertChannel is null) {
                await command.RespondAsync(
                    ephemeral: true,
                    text:      "No alert channel was configured for this server!");
                return;
            }

            db.Remove(alertChannel);

            await db.SaveChangesAsync();
            await db.Database.CommitTransactionAsync();

            await command.RespondAsync(
                ephemeral: true,
                text:      $"Removed the configured alert channel for this server");
        }

        private async Task OnSubscribeChannelCommand(SocketSlashCommand command) {
            using var scope = serviceProvider.CreateScope();
            using var db    = scope.ServiceProvider.GetRequiredService<PagerContext>();

            string mention = string.Empty;

            var subscription = new DiscordAlertSubscription() {
                GuildId         = (ulong) command.GuildId!,
                PageDestination = (string) command.Data.Options.Last().Value
            };

            switch(command.Data.Options.First().Value) {
                case SocketUser user:
                    subscription.PrincipalType = DiscordPrincipalType.User;
                    subscription.PrincipalId   = user.Id;
                    mention                    = $"<@!{user.Id}>";
                    break;
                case SocketRole role:
                    subscription.PrincipalType = DiscordPrincipalType.Role;
                    subscription.PrincipalId   = role.Id;
                    mention                    = $"<@&{role.Id}>";
                    break;
            }

            await db.Database.BeginTransactionAsync();

            var exists = db.DiscordAlertSubscriptions
                .Where(s => s.GuildId == command.GuildId)
                .Where(s => s.PrincipalType == subscription.PrincipalType)
                .Where(s => s.PrincipalId == subscription.PrincipalId)
                .Where(s => s.PageDestination == subscription.PageDestination)
                .Any();

            if(exists) {
                await command.RespondAsync(
                    ephemeral: true,
                    text: string.Join(' ', [
                        mention,
                        subscription.PrincipalType == DiscordPrincipalType.User ? "is" : "are",
                        "already subscribed to pager messages for",
                        $"`{subscription.PageDestination}`"
                    ]));
                return;
            }

            db.DiscordAlertSubscriptions.Add(subscription);
            await db.SaveChangesAsync();
            await db.Database.CommitTransactionAsync();

            await command.RespondAsync(
                ephemeral: true,
                text: string.Join(' ', [
                    "Subscribed",
                    $"<@{subscription.PrincipalId}>",
                    "to pager messages for",
                    $"`{subscription.PageDestination}`"
                ]));
        }

        private async Task OnUnsubscribeChannelCommand(SocketSlashCommand command) {
            using var scope = serviceProvider.CreateScope();
            using var db    = scope.ServiceProvider.GetRequiredService<PagerContext>();

            string mention = string.Empty;

            var subscription = new DiscordAlertSubscription() {
                GuildId         = (ulong) command.GuildId!,
                PageDestination = (string) command.Data.Options.Last().Value
            };

            switch(command.Data.Options.First().Value) {
                case SocketUser user:
                    subscription.PrincipalType = DiscordPrincipalType.User;
                    subscription.PrincipalId   = user.Id;
                    mention                    = $"<@!{user.Id}>";
                    break;
                case SocketRole role:
                    subscription.PrincipalType = DiscordPrincipalType.Role;
                    subscription.PrincipalId   = role.Id;
                    mention                    = $"<@&{role.Id}>";
                    break;
            }

            await db.Database.BeginTransactionAsync();

            var existing = db.DiscordAlertSubscriptions
                .Where(s => s.GuildId == command.GuildId)
                .Where(s => s.PrincipalType == subscription.PrincipalType)
                .Where(s => s.PrincipalId == subscription.PrincipalId)
                .Where(s => s.PageDestination == subscription.PageDestination);

            if(!existing.Any()) {
                await command.RespondAsync(
                    ephemeral: true,
                    text: string.Join(' ', [
                        mention,
                        subscription.PrincipalType == DiscordPrincipalType.User ? "was" : "are",
                        "not subscribed to pager messages for",
                        $"`{subscription.PageDestination}`"
                    ]));
                return;
            }

            db.DiscordAlertSubscriptions.RemoveRange(existing);
            await db.SaveChangesAsync();
            await db.Database.CommitTransactionAsync();

            await command.RespondAsync(
                ephemeral: true,
                text: string.Join(' ', [
                    "Unsubscribed",
                    $"<@{subscription.PrincipalId}>",
                    "from pager messages for",
                    $"`{subscription.PageDestination}`"
                ]));
        }

        private async Task OnListSubscriptionsCommand(SocketSlashCommand command) {
            using var scope = serviceProvider.CreateScope();
            using var db    = scope.ServiceProvider.GetRequiredService<PagerContext>();

            DiscordPrincipalType principalType;
            ulong                principalId;
            string               mention;

            switch(command.Data.Options.FirstOrDefault()?.Value) {
                case SocketUser user:
                    principalType = DiscordPrincipalType.User;
                    principalId   = user.Id;
                    mention       = $"<@!{user.Id}> is";
                    break;
                case SocketRole role:
                    principalType = DiscordPrincipalType.Role;
                    principalId   = role.Id;
                    mention       = $"<@&{role.Id}> are";
                    break;
                default:
                    principalType = DiscordPrincipalType.User;
                    principalId   = command.User.Id;
                    mention       = $"<@!{command.User.Id}> is";
                    break;
            }

            var subscriptions = db.DiscordAlertSubscriptions
                .Where(s => s.GuildId == command.GuildId)
                .Where(s => s.PrincipalType == principalType)
                .Where(s => s.PrincipalId == principalId)
                .OrderBy(s => s.PageDestination)
                .Select(s => s.PageDestination)
                .Distinct()
                .ToArray();

            if(subscriptions.Count() == 0) {
                await command.RespondAsync(
                    ephemeral: true,
                    text:      $"{mention} not subscribed to any pager messages");
                return;
            }

            await command.RespondAsync(
                ephemeral: true,
                text: string.Join(
                    "\n - ",
                    Enumerable.Concat(
                        [ $"{mention} subscribed to pager messages for the following brigades/appliances:" ],
                        subscriptions.Select(s => $"`{s}`"))));
        }

        private async Task OnSlashCommand(SocketSlashCommand command) {
            logger.LogDebug($"Slash command executed: {command.Data.Name}");

            try {
                // Search the list of command builders, find the command
                // that was executed and attempt to invoke it's handler.
                var builder = CommandBuilders
                    .First(cb => cb.Name == command.Data.Name);
                await builder.CommandHandler(command);
            } catch(Exception e) {
                // Handle any exceptions by writing a detailed error description
                // to the log and responding to the user with an message and identifier
                // that can be used to identify the corresponding log entry.
                var reference = string.Format("{0:X8}", Random.Shared.Next());
                logger.LogError(e, string.Join(' ', [
                    $"Error executing Discord slash command:",
                    command.Data.Name,
                    "(error reference:",
                    string.Format("{0:X8}", reference),
                    ")"
                ]));
                try {
                    await command.RespondAsync(
                        ephemeral: true,
                        text: string.Join(' ', [
                            "An unknown error occurred whilst attempting to execute the command.",
                                "Error reference:",
                                $"`{reference}`"
                        ]));
                } catch {}
            }
        }

        private async Task OnReady() {
            // Register slash commands
            try {
                await discordClient.BulkOverwriteGlobalApplicationCommandsAsync(
                    CommandBuilders.Select(b => b.Build()).ToArray());
            } catch(Exception e) {
                logger.LogError(
                    e,
                    "Error registering Discord slash commands");
            }
        }

        public void OnConfiguring(
            ILogger logger,
            IConfiguration config,
            IServiceProvider serviceProvider) {

            this.logger          = logger;
            this.serviceProvider = serviceProvider;

            botToken = config.GetValue<string>("PagerParser:DiscordBot:Token")!;

            if(botToken is null) {
                logger.LogError("No bot token configured");
                throw new InvalidOperationException("Bot token is null!");
            }
        }

        public async Task StartAsync(CancellationToken ct) {
            discordClient = new();

            discordClient.Ready                += OnReady;
            discordClient.SlashCommandExecuted += OnSlashCommand;

            await discordClient.LoginAsync(TokenType.Bot, botToken);
            await discordClient.StartAsync();
        }

        public async Task StopAsync(CancellationToken ct) {
            await discordClient.StopAsync();
            await discordClient.DisposeAsync();
        }

        private string Color(AnsiColor color, string text) {
            if(!string.IsNullOrEmpty(text))
                return $"\x1B[{(int) color}m{text}\x1B[0m";
            else
                return "";
        }

        private enum AnsiColor {
            Black     = 30, Red          = 31, Green      = 32, Yellow      = 33,
            Blue      = 34, Magenta      = 35, Cyan       = 36, LightGray   = 37,
            DarkGray  = 90, LightRed     = 91, LightGreen = 92, LightYellow = 93,
            LightBlue = 94, LightMagenta = 95, LightCyan  = 96, White       = 97,
        }

        private class CommandBuilder : SlashCommandBuilder {
            public Func<SocketSlashCommand, Task> CommandHandler { get; set; }
        }
    }

    [Index(nameof(GuildId), IsUnique = true)]
    public class DiscordAlertChannel {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int   DiscordAlertChannelId { get; set; }
        public ulong GuildId               { get; set; }
        public ulong ChannelId             { get; set; }
        public bool  RequireMention        { get; set; }
    }

    [Index(nameof(GuildId))]
    public class DiscordAlertSubscription {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int                  DiscordAlertSubscriptionId { get; set; }
        public string               PageDestination            { get; set; }
        public ulong                GuildId                    { get; set; }
        public ulong                PrincipalId                { get; set; }
        public DiscordPrincipalType PrincipalType              { get; set; }
    }

    public enum DiscordPrincipalType {
        User,
        Role
    }
}