#[cfg(feature = "model")]
use std::fmt::{Display, Formatter, Result as FmtResult};
#[cfg(feature = "model")]
use std::sync::Arc;

use chrono::{DateTime, Utc};
#[cfg(feature = "cache")]
use futures::stream::StreamExt;

#[cfg(feature = "model")]
use crate::builder::EditChannel;
#[cfg(feature = "model")]
use crate::builder::{
    CreateInvite,
    CreateMessage,
    CreateThread,
    EditMessage,
    EditVoiceState,
    GetMessages,
};
use crate::builder::{CreateStageInstance, EditStageInstance};
#[cfg(feature = "cache")]
use crate::cache::Cache;
#[cfg(feature = "collector")]
use crate::client::bridge::gateway::ShardMessenger;
#[cfg(feature = "collector")]
use crate::collector::{
    CollectReaction,
    CollectReply,
    MessageCollectorBuilder,
    ReactionCollectorBuilder,
};
#[cfg(feature = "model")]
use crate::http::AttachmentType;
#[cfg(feature = "model")]
use crate::http::{CacheHttp, Http, Typing};
#[cfg(all(feature = "cache", feature = "model"))]
use crate::internal::prelude::*;
use crate::model::prelude::*;
#[cfg(all(feature = "model", feature = "utils"))]
use crate::utils as serenity_utils;

/// Represents a guild's text, news, or voice channel. Some methods are available
/// only for voice channels and some are only available for text channels.
/// News channels are a subset of text channels and lack slow mode hence
/// [`Self::slow_mode_rate`] will be [`None`].
#[derive(Clone, Debug, Deserialize, Serialize)]
#[non_exhaustive]
pub struct GuildChannel {
    /// The unique Id of the channel.
    ///
    /// The default channel Id shares the Id of the guild and the default role.
    pub id: ChannelId,
    /// The bitrate of the channel.
    ///
    /// **Note**: This is only available for voice and stage channels.
    pub bitrate: Option<u64>,
    /// Whether this guild channel belongs in a category.
    #[serde(rename = "parent_id")]
    pub category_id: Option<ChannelId>,
    /// The Id of the guild the channel is located in.
    ///
    /// If this matches with the [`id`], then this is the default text channel.
    ///
    /// The original voice channel has an Id equal to the guild's Id,
    /// incremented by one.
    pub guild_id: GuildId,
    /// The type of the channel.
    #[serde(rename = "type")]
    pub kind: ChannelType,
    /// The Id of the last message sent in the channel.
    ///
    /// **Note**: This is only available for text channels.
    pub last_message_id: Option<MessageId>,
    /// The timestamp of the time a pin was most recently made.
    ///
    /// **Note**: This is only available for text channels.
    pub last_pin_timestamp: Option<DateTime<Utc>>,
    /// The name of the channel.
    pub name: String,
    /// Permission overwrites for [`Member`]s and for [`Role`]s.
    #[serde(default)]
    pub permission_overwrites: Vec<PermissionOverwrite>,
    /// The position of the channel.
    ///
    /// The default text channel will _almost always_ have a position of `-1` or
    /// `0`.
    #[serde(default)]
    pub position: i64,
    /// The topic of the channel.
    ///
    /// **Note**: This is only available for text and stage channels.
    pub topic: Option<String>,
    /// The maximum number of members allowed in the channel.
    ///
    /// **Note**: This is only available for voice channels.
    pub user_limit: Option<u64>,
    /// Used to tell if the channel is not safe for work.
    /// Note however, it's recommended to use [`Self::is_nsfw`] as it's gonna be more accurate.
    // This field can or can not be present sometimes, but if it isn't
    // default to `false`.
    #[serde(default)]
    pub nsfw: bool,
    /// A rate limit that applies per user and excludes bots.
    ///
    /// **Note**: This is only available for text channels excluding news
    /// channels.
    #[serde(default, rename = "rate_limit_per_user")]
    pub slow_mode_rate: Option<u64>,
    /// The region override.
    ///
    /// **Note**: This is only available for voice and stage channels. [`None`]
    /// for voice and stage channels means automatic region selection.
    pub rtc_region: Option<String>,
    /// The video quality mode for a voice channel.
    pub video_quality_mode: Option<VideoQualityMode>,
    /// An approximate count of messages in the thread, stops counting at 50.
    ///
    /// **Note**: This is only available on thread channels.
    pub message_count: Option<u8>,
    /// An approximate count of users in a thread, stops counting at 50.
    ///
    /// **Note**: This is only available on thread channels.
    pub member_count: Option<u8>,
    /// The thread metadata.
    ///
    /// **Note**: This is only available on thread channels.
    pub thread_metadata: Option<ThreadMetadata>,
    /// Thread member object for the current user, if they have joined the thread,
    /// only included on certain API endpoints.
    pub member: Option<ThreadMember>,
    /// Default duration for newly created threads, in minutes, to automatically
    /// archive the thread after recent activity.
    ///
    /// **Note**: It can currently only be set to 60, 1440, 4320, 10080.
    pub default_auto_archive_duration: Option<u64>,
}

#[cfg(feature = "model")]
impl GuildChannel {
    /// Whether or not this channel is text-based, meaning that
    /// it is possible to send messages.
    pub fn is_text_based(&self) -> bool {
        matches!(self.kind, ChannelType::Text | ChannelType::News)
    }

    /// Broadcasts to the channel that the current user is typing.
    ///
    /// For bots, this is a good indicator for long-running commands.
    ///
    /// **Note**: Requires the [Send Messages] permission.
    ///
    /// # Errors
    ///
    /// Returns [`Error::Http`] if the current user does
    /// not have the required permissions.
    ///
    /// [Send Messages]: Permissions::SEND_MESSAGES
    #[inline]
    pub async fn broadcast_typing(&self, http: impl AsRef<Http>) -> Result<()> {
        self.id.broadcast_typing(&http).await
    }

    /// Creates an invite leading to the given channel.
    ///
    /// **Note**: Requres the [Create Invite] permission.
    ///
    /// # Examples
    ///
    /// Create an invite that can only be used 5 times:
    ///
    /// ```rust,ignore
    /// let invite = channel.create_invite(&context, |i| i.max_uses(5)).await;
    /// ```
    ///
    /// # Errors
    ///
    /// If the `cache` is enabled, returns [`ModelError::InvalidPermissions`]
    /// if the current user does not have permission to create invites.
    ///
    /// Otherwise returns [`Error::Http`] if the current user lacks permission.
    ///
    /// [Create Instant Invite]: Permissions::CREATE_INVITE
    #[inline]
    #[cfg(feature = "utils")]
    pub async fn create_invite<F>(&self, cache_http: impl CacheHttp, f: F) -> Result<RichInvite>
    where
        F: FnOnce(&mut CreateInvite) -> &mut CreateInvite,
    {
        #[cfg(feature = "cache")]
        {
            if let Some(cache) = cache_http.cache() {
                utils::user_has_perms_cache(
                    cache,
                    self.id,
                    Some(self.guild_id),
                    Permissions::CREATE_INVITE,
                )
                .await?;
            }
        }

        self.id.create_invite(cache_http.http(), f).await
    }

    /// Creates a [permission overwrite][`PermissionOverwrite`] for either a
    /// single [`Member`] or [`Role`] within a [`Channel`].
    ///
    /// Refer to the documentation for [`PermissionOverwrite`]s for more
    /// information.
    ///
    /// Requires the [Manage Channels] permission.
    ///
    /// # Examples
    ///
    /// Creating a permission overwrite for a member by specifying the
    /// [`PermissionOverwriteType::Member`] variant, allowing it the [Send Messages]
    /// permission, but denying the [Send TTS Messages] and [Attach Files]
    /// permissions:
    ///
    /// ```rust,no_run
    /// # #[cfg(feature = "cache")]
    /// # async fn run() -> Result<(), Box<dyn std::error::Error>> {
    /// # use serenity::{cache::Cache, http::Http, model::id::{ChannelId, UserId}};
    /// # use tokio::sync::RwLock;
    /// # use std::sync::Arc;
    /// #
    /// #     let http = Arc::new(Http::default());
    /// #     let cache = Cache::default();
    /// #     let (channel_id, user_id) = (ChannelId(0), UserId(0));
    /// #
    /// use serenity::model::channel::{
    ///     PermissionOverwrite,
    ///     PermissionOverwriteType,
    /// };
    /// use serenity::model::{ModelError, Permissions};
    /// let allow = Permissions::SEND_MESSAGES;
    /// let deny = Permissions::SEND_TTS_MESSAGES | Permissions::ATTACH_FILES;
    /// let overwrite = PermissionOverwrite {
    ///     allow: allow,
    ///     deny: deny,
    ///     kind: PermissionOverwriteType::Member(user_id),
    /// };
    /// // assuming the cache has been unlocked
    /// let channel = cache
    ///     .guild_channel(channel_id)
    ///     .await
    ///     .ok_or(ModelError::ItemMissing)?;
    ///
    /// channel.create_permission(&http, &overwrite).await?;
    /// #   Ok(())
    /// # }
    /// ```
    ///
    /// Creating a permission overwrite for a role by specifying the
    /// [`PermissionOverwriteType::Role`] variant, allowing it the [Manage Webhooks]
    /// permission, but denying the [Send TTS Messages] and [Attach Files]
    /// permissions:
    ///
    /// ```rust,no_run
    /// # #[cfg(feature = "cache")]
    /// # async fn run() -> Result<(), Box<dyn std::error::Error>> {
    /// # use serenity::{cache::Cache, http::Http, model::id::{ChannelId, UserId}};
    /// # use tokio::sync::RwLock;
    /// # use std::sync::Arc;
    /// #
    /// #   let http = Arc::new(Http::default());
    /// #   let cache = Cache::default();
    /// #   let (channel_id, user_id) = (ChannelId(0), UserId(0));
    /// #
    /// use serenity::model::channel::{
    ///     PermissionOverwrite,
    ///     PermissionOverwriteType,
    /// };
    /// use serenity::model::{ModelError, Permissions, channel::Channel};
    ///
    /// let allow = Permissions::SEND_MESSAGES;
    /// let deny = Permissions::SEND_TTS_MESSAGES | Permissions::ATTACH_FILES;
    /// let overwrite = PermissionOverwrite {
    ///     allow: allow,
    ///     deny: deny,
    ///     kind: PermissionOverwriteType::Member(user_id),
    /// };
    ///
    /// let channel = cache
    ///     .guild_channel(channel_id)
    ///     .await
    ///     .ok_or(ModelError::ItemMissing)?;
    ///
    /// channel.create_permission(&http, &overwrite).await?;
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// # Errors
    ///
    /// Returns [`Error::Http`] if the current user lacks permission.
    ///
    /// [Attach Files]: Permissions::ATTACH_FILES
    /// [Manage Channels]: Permissions::MANAGE_CHANNELS
    /// [Manage Webhooks]: Permissions::MANAGE_WEBHOOKS
    /// [Send Messages]: Permissions::SEND_MESSAGES
    /// [Send TTS Messages]: Permissions::SEND_TTS_MESSAGES
    #[inline]
    pub async fn create_permission(
        &self,
        http: impl AsRef<Http>,
        target: &PermissionOverwrite,
    ) -> Result<()> {
        self.id.create_permission(&http, target).await
    }

    /// Deletes this channel, returning the channel on a successful deletion.
    ///
    /// **Note**: Requres the [Manage Channels] permission.
    ///
    /// # Errors
    ///
    /// If the `cache` is enabled, returns [`ModelError::InvalidPermissions`]
    /// if the current user does not have permission.
    ///
    /// Otherwise returns [`Error::Http`] if the current user lacks permission.
    ///
    /// [Manage Channels]: Permissions::MANAGE_CHANNELS
    pub async fn delete(&self, cache_http: impl CacheHttp) -> Result<Channel> {
        #[cfg(feature = "cache")]
        {
            if let Some(cache) = cache_http.cache() {
                utils::user_has_perms_cache(
                    cache,
                    self.id,
                    Some(self.guild_id),
                    Permissions::MANAGE_CHANNELS,
                )
                .await?;
            }
        }

        self.id.delete(&cache_http.http()).await
    }

    /// Deletes all messages by Ids from the given vector in the channel.
    ///
    /// The minimum amount of messages is 2 and the maximum amount is 100.
    ///
    /// Requires the [Manage Messages] permission.
    ///
    /// **Note**: Messages that are older than 2 weeks can't be deleted using
    /// this method.
    ///
    /// # Errors
    ///
    /// Returns [`ModelError::BulkDeleteAmount`] if an attempt was made to
    /// delete either 0 or more than 100 messages.
    ///
    /// [Manage Messages]: Permissions::MANAGE_MESSAGES
    #[inline]
    pub async fn delete_messages<T, It>(
        &self,
        http: impl AsRef<Http>,
        message_ids: It,
    ) -> Result<()>
    where
        T: AsRef<MessageId>,
        It: IntoIterator<Item = T>,
    {
        self.id.delete_messages(&http, message_ids).await
    }

    /// Deletes all permission overrides in the channel from a member
    /// or role.
    ///
    /// **Note**: Requires the [Manage Channel] permission.
    ///
    /// # Errors
    ///
    /// Returns [`Error::Http`] if the current user lacks permission.
    ///
    /// [Manage Channel]: Permissions::MANAGE_CHANNELS
    #[inline]
    pub async fn delete_permission(
        &self,
        http: impl AsRef<Http>,
        permission_type: PermissionOverwriteType,
    ) -> Result<()> {
        self.id.delete_permission(&http, permission_type).await
    }

    /// Deletes the given [`Reaction`] from the channel.
    ///
    /// **Note**: Requires the [Manage Messages] permission, _if_ the current
    /// user did not perform the reaction.
    ///
    /// # Errors
    ///
    /// Returns [`Error::Http`] if the current user lacks permission.
    /// [Manage Messages]: Permissions::MANAGE_MESSAGES
    #[inline]
    pub async fn delete_reaction(
        &self,
        http: impl AsRef<Http>,
        message_id: impl Into<MessageId>,
        user_id: Option<UserId>,
        reaction_type: impl Into<ReactionType>,
    ) -> Result<()> {
        self.id.delete_reaction(&http, message_id, user_id, reaction_type).await
    }

    /// Modifies a channel's settings, such as its position or name.
    ///
    /// Refer to [`EditChannel`]s documentation for a full list of methods.
    ///
    /// # Examples
    ///
    /// Change a voice channels name and bitrate:
    ///
    /// ```rust,ignore
    /// channel.edit(&context, |c| c.name("test").bitrate(86400)).await;
    /// ```
    ///
    /// # Errors
    ///
    /// If the `cache` is enabled, returns [ModelError::InvalidPermissions]
    /// if the current user lacks permission to edit the channel.
    ///
    /// Otherwise returns [`Error::Http`] if the current user lacks permission.
    #[cfg(feature = "utils")]
    pub async fn edit<F>(&mut self, cache_http: impl CacheHttp, f: F) -> Result<()>
    where
        F: FnOnce(&mut EditChannel) -> &mut EditChannel,
    {
        #[cfg(feature = "cache")]
        {
            if let Some(cache) = cache_http.cache() {
                utils::user_has_perms_cache(
                    cache,
                    self.id,
                    Some(self.guild_id),
                    Permissions::MANAGE_CHANNELS,
                )
                .await?;
            }
        }

        let mut map = HashMap::new();
        map.insert("name", Value::String(self.name.clone()));
        map.insert("position", Value::Number(Number::from(self.position)));

        let mut edit_channel = EditChannel::default();
        f(&mut edit_channel);
        let edited = serenity_utils::hashmap_to_json_map(edit_channel.0);

        *self = cache_http.http().edit_channel(self.id.0, &edited).await?;

        Ok(())
    }

    /// Edits a [`Message`] in the channel given its Id.
    ///
    /// Message editing preserves all unchanged message data.
    ///
    /// Refer to the documentation for [`EditMessage`] for more information
    /// regarding message restrictions and requirements.
    ///
    /// **Note**: Requires that the current user be the author of the message.
    ///
    /// # Errors
    ///
    /// Returns a [`ModelError::MessageTooLong`] if the content of the message
    /// is over the [`the limit`], containing the number of unicode code points
    /// over the limit.
    ///
    /// [`EditMessage`]: crate::builder::EditMessage
    /// [`the limit`]: crate::builder::EditMessage::content
    #[inline]
    pub async fn edit_message<F>(
        &self,
        http: impl AsRef<Http>,
        message_id: impl Into<MessageId>,
        f: F,
    ) -> Result<Message>
    where
        F: FnOnce(&mut EditMessage) -> &mut EditMessage,
    {
        self.id.edit_message(&http, message_id, f).await
    }

    /// Edits a voice state in a stage channel. Pass [`None`] for `user_id` to
    /// edit the current user's voice state.
    ///
    /// Requires the [Mute Members] permission to suppress another user or
    /// unsuppress the current user. This is not required if suppressing
    /// the current user.
    ///
    /// Requires the [Request to Speak] permission.
    ///
    /// # Example
    ///
    /// Invite a user to speak.
    ///
    /// ```rust
    /// # #[cfg(feature = "cache")]
    /// # async fn run() -> Result<(), Box<dyn std::error::Error>> {
    /// # use std::sync::Arc;
    /// # use serenity::{cache::Cache, http::Http, model::id::{ChannelId, UserId}};
    /// #
    /// #     let http = Arc::new(Http::default());
    /// #     let cache = Cache::default();
    /// #     let (channel_id, user_id) = (ChannelId(0), UserId(0));
    /// #
    /// use serenity::model::ModelError;
    ///
    /// // assuming the cache has been unlocked
    /// let channel = cache.guild_channel(channel_id).await.ok_or(ModelError::ItemMissing)?;
    ///
    /// channel.edit_voice_state(&http, user_id, |v| v.suppress(false)).await?;
    /// #   Ok(())
    /// # }
    /// ```
    ///
    /// # Errors
    ///
    /// Returns a [`ModelError::InvalidChannelType`] if the channel type is not
    /// stage.
    ///
    /// [Mute Members]: crate::model::permissions::Permissions::MUTE_MEMBERS
    /// [Request to Speak]: crate::model::permissions::Permissions::REQUEST_TO_SPEAK
    pub async fn edit_voice_state<F>(
        &self,
        http: impl AsRef<Http>,
        user_id: impl Into<UserId>,
        f: F,
    ) -> Result<()>
    where
        F: FnOnce(&mut EditVoiceState) -> &mut EditVoiceState,
    {
        self._edit_voice_state(http, Some(user_id), f).await
    }

    /// Edits the current user's voice state in a stage channel.
    ///
    /// The [Mute Members] permission is **not** required if suppressing the
    /// current user.
    ///
    /// Requires the [Request to Speak] permission.
    ///
    /// # Example
    ///
    /// Send a request to speak, then clear the request.
    ///
    /// ```rust
    /// # #[cfg(feature = "cache")]
    /// # async fn run() -> Result<(), Box<dyn std::error::Error>> {
    /// # use std::sync::Arc;
    /// # use serenity::{cache::Cache, http::Http, model::id::ChannelId};
    /// #
    /// #     let http = Arc::new(Http::default());
    /// #     let cache = Cache::default();
    /// #     let channel_id = ChannelId(0);
    /// #
    /// use serenity::model::ModelError;
    ///
    /// // assuming the cache has been unlocked
    /// let channel = cache.guild_channel(channel_id).await.ok_or(ModelError::ItemMissing)?;
    ///
    /// // Send a request to speak
    /// channel.edit_own_voice_state(&http, |v| v.request_to_speak(true)).await?;
    ///
    /// // Clear own request to speak
    /// channel.edit_own_voice_state(&http, |v| v.request_to_speak(false)).await?;
    /// #   Ok(())
    /// # }
    /// ```
    ///
    /// # Errors
    ///
    /// Returns a [`ModelError::InvalidChannelType`] if the channel type is not
    /// stage.
    ///
    /// [Mute Members]: crate::model::permissions::Permissions::MUTE_MEMBERS
    /// [Request to Speak]: crate::model::permissions::Permissions::REQUEST_TO_SPEAK
    pub async fn edit_own_voice_state<F>(&self, http: impl AsRef<Http>, f: F) -> Result<()>
    where
        F: FnOnce(&mut EditVoiceState) -> &mut EditVoiceState,
    {
        self._edit_voice_state(http, None::<u64>, f).await
    }

    async fn _edit_voice_state<F>(
        &self,
        http: impl AsRef<Http>,
        user_id: Option<impl Into<UserId>>,
        f: F,
    ) -> Result<()>
    where
        F: FnOnce(&mut EditVoiceState) -> &mut EditVoiceState,
    {
        if self.kind != ChannelType::Stage {
            return Err(Error::from(ModelError::InvalidChannelType));
        }

        let mut voice_state = EditVoiceState::default();
        f(&mut voice_state);

        voice_state.0.insert("channel_id", Value::String(self.id.0.to_string()));

        let map = serenity_utils::hashmap_to_json_map(voice_state.0);

        if let Some(id) = user_id {
            http.as_ref().edit_voice_state(self.guild_id.0, id.into().0, &map).await
        } else {
            http.as_ref().edit_voice_state_me(self.guild_id.0, &map).await
        }
    }

    /// Attempts to find this channel's guild in the Cache.
    #[cfg(feature = "cache")]
    #[inline]
    pub async fn guild(&self, cache: impl AsRef<Cache>) -> Option<Guild> {
        cache.as_ref().guild(self.guild_id).await
    }

    /// Gets all of the channel's invites.
    ///
    /// Requires the [Manage Channels] permission.
    ///
    /// # Errors
    ///
    /// Returns [`Error::Http`] if the current user lacks permission.
    ///
    /// [Manage Channels]: Permissions::MANAGE_CHANNELS
    #[inline]
    pub async fn invites(&self, http: impl AsRef<Http>) -> Result<Vec<RichInvite>> {
        self.id.invites(&http).await
    }

    /// Determines if the channel is NSFW.
    ///
    /// Only [text channels][`ChannelType::Text`] are taken into consideration
    /// as being NSFW. [voice channels][`ChannelType::Voice`] are never NSFW.
    #[inline]
    pub fn is_nsfw(&self) -> bool {
        self.kind == ChannelType::Text && self.nsfw
    }

    /// Gets a message from the channel.
    ///
    /// Requires the [Read Message History] permission.
    ///
    /// # Errors
    ///
    /// Returns [`Error::Http`] if the current user lacks permission,
    /// or if a message with the given Id does not exist in the channel.
    ///
    /// [Read Message History]: Permissions::READ_MESSAGE_HISTORY
    #[inline]
    pub async fn message(
        &self,
        http: impl AsRef<Http>,
        message_id: impl Into<MessageId>,
    ) -> Result<Message> {
        self.id.message(&http, message_id).await
    }

    /// Gets messages from the channel.
    ///
    /// Refer to the [`GetMessages`]-builder for more information on how to
    /// use `builder`.
    ///
    /// **Note**: Returns an empty [`Vec`] if the current user does not have the
    /// [Read Message History] permission.
    ///
    /// # Errors
    ///
    /// Returns [`Error::Http`] if the current user lacks permission to
    /// view the channel.
    ///
    /// [`GetMessages`]: crate::builder::GetMessages
    /// [Read Message History]: Permissions::READ_MESSAGE_HISTORY
    #[inline]
    pub async fn messages<F>(&self, http: impl AsRef<Http>, builder: F) -> Result<Vec<Message>>
    where
        F: FnOnce(&mut GetMessages) -> &mut GetMessages,
    {
        self.id.messages(&http, builder).await
    }

    /// Returns the name of the guild channel.
    pub fn name(&self) -> &str {
        &self.name
    }

    /// Calculates the permissions of a member.
    ///
    /// The Id of the argument must be a [`Member`] of the [`Guild`] that the
    /// channel is in.
    ///
    /// # Examples
    ///
    /// Calculate the permissions of a [`User`] who posted a [`Message`] in a
    /// channel:
    ///
    /// ```rust,no_run
    /// use serenity::prelude::*;
    /// use serenity::model::prelude::*;
    /// struct Handler;
    ///
    /// #[serenity::async_trait]
    /// impl EventHandler for Handler {
    ///     async fn message(&self, context: Context, msg: Message) {
    ///         let channel = match context.cache.guild_channel(msg.channel_id).await {
    ///             Some(channel) => channel,
    ///             None => return,
    ///         };
    ///
    ///         if let Ok(permissions) = channel.permissions_for_user(&context.cache, &msg.author).await {
    ///             println!("The user's permissions: {:?}", permissions);
    ///         }
    ///     }
    /// }
    ///
    /// # async fn run() -> Result<(), Box<dyn std::error::Error>> {
    /// let mut client =Client::builder("token").event_handler(Handler).await?;
    ///
    /// client.start().await?;
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// Check if the current user has the [Attach Files] and [Send Messages]
    /// permissions (note: serenity will automatically check this for; this is
    /// for demonstrative purposes):
    ///
    /// ```rust,no_run
    /// use serenity::prelude::*;
    /// use serenity::model::prelude::*;
    /// use serenity::model::channel::Channel;
    /// use tokio::fs::File;
    ///
    /// struct Handler;
    ///
    /// #[serenity::async_trait]
    /// impl EventHandler for Handler {
    ///     async fn message(&self, context: Context, mut msg: Message) {
    ///         let channel = match context.cache.guild_channel(msg.channel_id).await {
    ///             Some(channel) => channel,
    ///             None => return,
    ///         };
    ///
    ///         let current_user_id = context.cache.current_user().await.id;
    ///         if let Ok(permissions) = channel.permissions_for_user(&context.cache, current_user_id).await {
    ///
    ///             if !permissions.contains(Permissions::ATTACH_FILES | Permissions::SEND_MESSAGES) {
    ///                 return;
    ///             }
    ///
    ///             let file = match File::open("./cat.png").await {
    ///                 Ok(file) => file,
    ///                 Err(why) => {
    ///                     println!("Err opening file: {:?}", why);
    ///
    ///                     return;
    ///                 },
    ///             };
    ///
    ///             let _ = msg.channel_id.send_files(&context.http, vec![(&file, "cat.png")], |mut m| {
    ///                 m.content("here's a cat");
    ///                 m
    ///             })
    ///             .await;
    ///         }
    ///     }
    /// }
    ///
    /// # async fn run() -> Result<(), Box<dyn std::error::Error>> {
    /// let mut client =Client::builder("token").event_handler(Handler).await?;
    ///
    /// client.start().await?;
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// # Errors
    ///
    /// Returns a [`ModelError::GuildNotFound`] if the channel's guild could
    /// not be found in the [`Cache`].
    ///
    /// [Attach Files]: Permissions::ATTACH_FILES
    /// [Send Messages]: Permissions::SEND_MESSAGES
    #[cfg(feature = "cache")]
    #[inline]
    pub async fn permissions_for_user(
        &self,
        cache: impl AsRef<Cache>,
        user_id: impl Into<UserId>,
    ) -> Result<Permissions> {
        let guild = self.guild(&cache).await.ok_or(Error::Model(ModelError::GuildNotFound))?;
        let member =
            guild.members.get(&user_id.into()).ok_or(Error::Model(ModelError::MemberNotFound))?;
        guild.user_permissions_in(self, member)
    }

    /// Calculates the permissions of a role.
    ///
    /// The Id of the argument must be a [`Role`] of the [`Guild`] that the
    /// channel is in.
    ///
    /// # Errors
    ///
    /// Returns a [`ModelError::GuildNotFound`] if the channel's guild could
    /// not be found in the [`Cache`].
    ///
    /// Returns a [`ModelError::RoleNotFound`] if the given role could not
    /// be found in the [`Cache`].
    #[cfg(feature = "cache")]
    #[inline]
    pub async fn permissions_for_role(
        &self,
        cache: impl AsRef<Cache>,
        role_id: impl Into<RoleId>,
    ) -> Result<Permissions> {
        let guild = self.guild(&cache).await.ok_or(Error::Model(ModelError::GuildNotFound))?;
        let role =
            guild.roles.get(&role_id.into()).ok_or(Error::Model(ModelError::RoleNotFound))?;
        guild.role_permissions_in(self, role)
    }

    /// Pins a [`Message`] to the channel.
    ///
    /// **Note**: Requires the [Manage Messages] permission.
    ///
    /// # Errors
    ///
    /// Returns [`Error::Http`] if the current user lacks permission,
    /// or if the channel already has too many pinned messages.
    ///
    /// [Manage Messages]: Permissions::MANAGE_MESSAGES
    #[inline]
    pub async fn pin(
        &self,
        http: impl AsRef<Http>,
        message_id: impl Into<MessageId>,
    ) -> Result<()> {
        self.id.pin(&http, message_id).await
    }

    /// Gets all channel's pins.
    ///
    /// **Note**: If the current user lacks the [Read Message History] permission
    /// an empty [`Vec`] will be returned.
    ///
    /// # Errors
    ///
    /// Returns [`Error::Http`] if the current user lacks permission to view the channel.
    ///
    /// [Read Message History]: Permissions::READ_MESSAGE_HISTORY
    #[inline]
    pub async fn pins(&self, http: impl AsRef<Http>) -> Result<Vec<Message>> {
        self.id.pins(&http).await
    }

    /// Gets the list of [`User`]s who have reacted to a [`Message`] with a
    /// certain [`Emoji`].
    ///
    /// The default `limit` is `50` - specify otherwise to receive a different
    /// maximum number of users. The maximum that may be retrieve at a time is
    /// `100`, if a greater number is provided then it is automatically reduced.
    ///
    /// The optional `after` attribute is to retrieve the users after a certain
    /// user. This is useful for pagination.
    ///
    /// **Note**: Requires the [Read Message History] permission.
    ///
    /// # Errors
    ///
    /// Returns [`Error::Http`] if the current user lacks permission.
    ///
    /// [Read Message History]: Permissions::READ_MESSAGE_HISTORY
    pub async fn reaction_users(
        &self,
        http: impl AsRef<Http>,
        message_id: impl Into<MessageId>,
        reaction_type: impl Into<ReactionType>,
        limit: Option<u8>,
        after: impl Into<Option<UserId>>,
    ) -> Result<Vec<User>> {
        self.id.reaction_users(&http, message_id, reaction_type, limit, after).await
    }

    /// Sends a message with just the given message content in the channel.
    ///
    /// # Errors
    ///
    /// Returns a [`ModelError::MessageTooLong`] if the content of the message
    /// is over the above limit, containing the number of unicode code points
    /// over the limit.
    ///
    /// May also return [`Error::Http`] if the current user lacks permission
    /// to send a message to the channel.
    #[inline]
    pub async fn say(
        &self,
        http: impl AsRef<Http>,
        content: impl std::fmt::Display,
    ) -> Result<Message> {
        self.id.say(&http, content).await
    }

    /// Sends (a) file(s) along with optional message contents.
    ///
    /// Refer to [`ChannelId::send_files`] for examples and more information.
    ///
    /// The [Attach Files] and [Send Messages] permissions are required.
    ///
    /// **Note**: Message contents must be under 2000 unicode code points.
    ///
    /// # Errors
    ///
    /// If the content of the message is over the above limit, then a
    /// [`ModelError::MessageTooLong`] will be returned, containing the number
    /// of unicode code points over the limit.
    ///
    /// [Attach Files]: Permissions::ATTACH_FILES
    /// [Send Messages]: Permissions::SEND_MESSAGES
    #[inline]
    pub async fn send_files<'a, F, T, It>(
        &self,
        http: impl AsRef<Http>,
        files: It,
        f: F,
    ) -> Result<Message>
    where
        for<'b> F: FnOnce(&'b mut CreateMessage<'a>) -> &'b mut CreateMessage<'a>,
        T: Into<AttachmentType<'a>>,
        It: IntoIterator<Item = T>,
    {
        self.id.send_files(&http, files, f).await
    }

    /// Sends a message to the channel with the given content.
    ///
    /// **Note**: This will only work when a [`Message`] is received.
    ///
    /// **Note**: Requires the [Send Messages] permission.
    ///
    /// # Errors
    ///
    /// Returns a [`ModelError::MessageTooLong`] if the content of the message
    /// is over the above limit, containing the number of unicode code points
    /// over the limit.
    ///
    /// If the `cache` is enabled, returns a [`ModelError::InvalidPermissions`] if the current user does
    /// not have the required permissions.
    ///
    /// Otherwise will return [`Error::Http`] if the current user lacks permission.
    ///
    /// [Send Messages]: Permissions::SEND_MESSAGES
    pub async fn send_message<'a, F>(&self, cache_http: impl CacheHttp, f: F) -> Result<Message>
    where
        for<'b> F: FnOnce(&'b mut CreateMessage<'a>) -> &'b mut CreateMessage<'a>,
    {
        #[cfg(feature = "cache")]
        {
            if let Some(cache) = cache_http.cache() {
                let req = Permissions::SEND_MESSAGES;

                if let Ok(false) =
                    utils::user_has_perms(&cache, self.id, Some(self.guild_id), req).await
                {
                    return Err(Error::Model(ModelError::InvalidPermissions(req)));
                }
            }
        }

        self.id.send_message(&cache_http.http(), f).await
    }

    /// Starts typing in the channel for an indefinite period of time.
    ///
    /// Returns [`Typing`] that is used to trigger the typing. [`Typing::stop`] must be called
    /// on the returned struct to stop typing. Note that on some clients, typing may persist
    /// for a few seconds after [`Typing::stop`] is called.
    /// Typing is also stopped when the struct is dropped.
    ///
    /// If a message is sent while typing is triggered, the user will stop typing for a brief period
    /// of time and then resume again until either [`Typing::stop`] is called or the struct is dropped.
    ///
    /// This should rarely be used for bots, although it is a good indicator that a
    /// long-running command is still being processed.
    ///
    /// ## Examples
    ///
    /// ```rust,no_run
    /// # #[cfg(feature = "cache")]
    /// # async fn run() -> Result<(), Box<dyn std::error::Error>> {
    /// # use serenity::{
    /// #    cache::Cache,
    /// #    http::{Http, Typing},
    /// #    model::{ModelError, channel::GuildChannel, id::ChannelId},
    /// #    Result,
    /// # };
    /// # use std::sync::Arc;
    /// #
    /// # fn long_process() {}
    /// # let http = Arc::new(Http::default());
    /// # let cache = Cache::default();
    /// # let channel = cache
    /// #    .guild_channel(ChannelId(7))
    /// #    .await.ok_or(ModelError::ItemMissing)?;
    /// // Initiate typing (assuming http is `Arc<Http>` and `channel` is bound)
    /// let typing = channel.start_typing(&http)?;
    ///
    /// // Run some long-running process
    /// long_process();
    ///
    /// // Stop typing
    /// typing.stop();
    /// #
    /// # Ok(())
    /// # }
    /// ```
    #[allow(clippy::missing_errors_doc)]
    pub fn start_typing(self, http: &Arc<Http>) -> Result<Typing> {
        http.start_typing(self.id.0)
    }

    /// Unpins a [`Message`] in the channel given by its Id.
    ///
    /// Requires the [Manage Messages] permission.
    ///
    /// # Errors
    ///
    /// Returns [`Error::Http`] if the current user lacks permission.
    ///
    /// [Manage Messages]: Permissions::MANAGE_MESSAGES
    #[inline]
    pub async fn unpin(
        &self,
        http: impl AsRef<Http>,
        message_id: impl Into<MessageId>,
    ) -> Result<()> {
        self.id.unpin(&http, message_id).await
    }

    /// Retrieves the channel's webhooks.
    ///
    /// **Note**: Requires the [Manage Webhooks] permission.
    ///
    /// # Errors
    ///
    /// Returns [`Error::Http`] if the current user lacks permission.
    ///
    /// [Manage Webhooks]: Permissions::MANAGE_WEBHOOKS
    #[inline]
    pub async fn webhooks(&self, http: impl AsRef<Http>) -> Result<Vec<Webhook>> {
        self.id.webhooks(&http).await
    }

    /// Retrieves [`Member`]s from the current channel.
    ///
    /// [`ChannelType::Voice`] and [`ChannelType::Stage`] returns [`Member`]s
    /// using the channel.
    ///
    /// [`ChannelType::Text`] and [`ChannelType::News`] return [`Member`]s that
    /// can read the channel.
    ///
    /// # Errors
    ///
    /// Other [`ChannelType`]s lack the concept of [`Member`]s and
    /// will return: [`ModelError::InvalidChannelType`].
    #[cfg(feature = "cache")]
    #[inline]
    pub async fn members(&self, cache: impl AsRef<Cache>) -> Result<Vec<Member>> {
        let cache = cache.as_ref();
        let guild = cache.guild(self.guild_id).await.ok_or(ModelError::GuildNotFound)?;

        match self.kind {
            ChannelType::Voice | ChannelType::Stage => Ok(guild
                .voice_states
                .values()
                .filter_map(|v| {
                    v.channel_id.and_then(|c| {
                        if c == self.id {
                            guild.members.get(&v.user_id).cloned()
                        } else {
                            None
                        }
                    })
                })
                .collect()),
            ChannelType::News | ChannelType::Text => {
                Ok(futures::stream::iter(guild.members.iter())
                    .filter_map(|e| async move {
                        if self
                            .permissions_for_user(cache, e.0)
                            .await
                            .map(|p| p.contains(Permissions::READ_MESSAGES))
                            .unwrap_or(false)
                        {
                            Some(e.1.clone())
                        } else {
                            None
                        }
                    })
                    .collect::<Vec<Member>>()
                    .await)
            },
            _ => Err(Error::from(ModelError::InvalidChannelType)),
        }
    }

    /// Returns a future that will await one message by this guild channel.
    #[cfg(feature = "collector")]
    #[cfg_attr(docsrs, doc(cfg(feature = "collector")))]
    pub fn await_reply<'a>(
        &self,
        shard_messenger: &'a impl AsRef<ShardMessenger>,
    ) -> CollectReply<'a> {
        CollectReply::new(shard_messenger).channel_id(self.id.0)
    }

    /// Returns a stream builder which can be awaited to obtain a stream of messages sent by this guild channel.
    #[cfg(feature = "collector")]
    #[cfg_attr(docsrs, doc(cfg(feature = "collector")))]
    pub fn await_replies<'a>(
        &self,
        shard_messenger: &'a impl AsRef<ShardMessenger>,
    ) -> MessageCollectorBuilder<'a> {
        MessageCollectorBuilder::new(shard_messenger).channel_id(self.id.0)
    }

    /// Await a single reaction by this guild channel.
    #[cfg(feature = "collector")]
    #[cfg_attr(docsrs, doc(cfg(feature = "collector")))]
    pub fn await_reaction<'a>(
        &self,
        shard_messenger: &'a impl AsRef<ShardMessenger>,
    ) -> CollectReaction<'a> {
        CollectReaction::new(shard_messenger).channel_id(self.id.0)
    }

    /// Returns a stream builder which can be awaited to obtain a stream of reactions sent by this guild channel.
    #[cfg(feature = "collector")]
    #[cfg_attr(docsrs, doc(cfg(feature = "collector")))]
    pub fn await_reactions<'a>(
        &self,
        shard_messenger: &'a impl AsRef<ShardMessenger>,
    ) -> ReactionCollectorBuilder<'a> {
        ReactionCollectorBuilder::new(shard_messenger).channel_id(self.id.0)
    }

    /// Creates a webhook with only a name.
    ///
    /// # Errors
    ///
    /// Returns a [`ModelError::NameTooShort`] if the name of the webhook is
    /// under the limit of 2 characters.
    /// Returns a [`ModelError::NameTooLong`] if the name of the webhook is
    /// over the limit of 100 characters.
    /// Returns a [`ModelError::InvalidChannelType`] if the channel type is not text.
    pub async fn create_webhook(
        &self,
        http: impl AsRef<Http>,
        name: impl std::fmt::Display,
    ) -> Result<Webhook> {
        let name = name.to_string();

        if name.len() < 2 {
            return Err(Error::Model(ModelError::NameTooShort));
        } else if name.len() > 100 {
            return Err(Error::Model(ModelError::NameTooLong));
        } else if !self.is_text_based() {
            return Err(Error::Model(ModelError::InvalidChannelType));
        }

        self.id.create_webhook(&http, name).await
    }

    /// Creates a webhook with a name and an avatar.
    ///
    /// # Errors
    ///
    /// In addition to the reasons [`Self::create_webhook`] may return an [`Error::Http`],
    /// if the image is too large.
    pub async fn create_webhook_with_avatar<'a>(
        &self,
        http: impl AsRef<Http>,
        name: impl std::fmt::Display,
        avatar: impl Into<AttachmentType<'a>>,
    ) -> Result<Webhook> {
        let name = name.to_string();
        let avatar = avatar.into();

        if name.len() < 2 {
            return Err(Error::Model(ModelError::NameTooShort));
        } else if name.len() > 100 {
            return Err(Error::Model(ModelError::NameTooLong));
        } else if !self.is_text_based() {
            return Err(Error::Model(ModelError::InvalidChannelType));
        }

        self.id.create_webhook_with_avatar(&http, name, avatar).await
    }

    /// Gets a stage instance.
    ///
    /// # Errors
    ///
    /// Returns [`ModelError::InvalidChannelType`] if the channel is not a stage channel.
    /// Returns [`Error::Http`] if there is no stage instance currently.
    pub async fn get_stage_instance(&self, http: impl AsRef<Http>) -> Result<StageInstance> {
        if self.kind.num() != 13 {
            return Err(Error::Model(ModelError::InvalidChannelType));
        }

        self.id.get_stage_instance(http).await
    }

    /// Creates a stage instance.
    ///
    /// # Errors
    ///
    /// Returns [`ModelError::InvalidChannelType`] if the channel is not a stage channel.
    /// Returns [`Error::Http`] if there is already a stage instance currently.
    pub async fn create_stage_instance<F>(
        &self,
        http: impl AsRef<Http>,
        f: F,
    ) -> Result<StageInstance>
    where
        F: FnOnce(&mut CreateStageInstance) -> &mut CreateStageInstance,
    {
        if self.kind.num() != 13 {
            return Err(Error::Model(ModelError::InvalidChannelType));
        }

        self.id.create_stage_instance(http, f).await
    }

    /// Edits a stage instance.
    ///
    /// # Errors
    ///
    /// Returns [`ModelError::InvalidChannelType`] if the channel is not a stage channel.
    /// Returns [`Error::Http`] if there is no stage instance currently.
    pub async fn edit_stage_instance<F>(
        &self,
        http: impl AsRef<Http>,
        f: F,
    ) -> Result<StageInstance>
    where
        F: FnOnce(&mut EditStageInstance) -> &mut EditStageInstance,
    {
        if self.kind.num() != 13 {
            return Err(Error::Model(ModelError::InvalidChannelType));
        }

        self.id.edit_stage_instance(http, f).await
    }

    /// Deletes a stage instance.
    ///
    /// # Errors
    ///
    /// Returns [`ModelError::InvalidChannelType`] if the channel is not a stage channel.
    /// Returns [`Error::Http`] if there is no stage instance currently.
    pub async fn delete_stage_instance(&self, http: impl AsRef<Http>) -> Result<()> {
        if self.kind.num() != 13 {
            return Err(Error::Model(ModelError::InvalidChannelType));
        }

        self.id.delete_stage_instance(http).await
    }

    /// Creates a public thread that is connected to a message.
    ///
    /// # Errors
    ///
    /// Returns [`Error::Http`] if the current user lacks permission.
    pub async fn create_public_thread<F>(
        &self,
        http: impl AsRef<Http>,
        message_id: impl Into<MessageId>,
        f: F,
    ) -> Result<GuildChannel>
    where
        F: FnOnce(&mut CreateThread) -> &mut CreateThread,
    {
        self.id.create_public_thread(http, message_id, f).await
    }

    /// Creates a private thread.
    ///
    /// # Errors
    ///
    /// Returns [`Error::Http`] if the current user lacks permission.
    pub async fn create_private_thread<F>(
        &self,
        http: impl AsRef<Http>,
        f: F,
    ) -> Result<GuildChannel>
    where
        F: FnOnce(&mut CreateThread) -> &mut CreateThread,
    {
        self.id.create_private_thread(http, f).await
    }
}

impl Display for GuildChannel {
    /// Formats the channel, creating a mention of it.
    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
        Display::fmt(&self.id.mention(), f)
    }
}

/// A partial guild channel.
#[derive(Clone, Debug, Deserialize, Serialize)]
pub struct PartialGuildChannel {
    /// The channel Id.
    pub id: ChannelId,
    /// The channel guild Id.
    pub guild_id: GuildId,
    /// The channel category Id.
    #[serde(rename = "parent_id")]
    pub category_id: ChannelId,
    /// The channel type.
    #[serde(rename = "type")]
    pub kind: ChannelType,
}