use std::collections::HashMap;

use chrono::Utc;
use serde::Deserialize;
use serde_json::{Value as JsonValue};
use uuid::Uuid;

use mitra_config::{Config, Instance};
use mitra_models::{
    attachments::queries::create_attachment,
    database::{DatabaseClient, DatabaseError},
    emojis::queries::{
        create_emoji,
        get_emoji_by_remote_object_id,
        update_emoji,
    },
    emojis::types::{DbEmoji, EmojiImage},
    posts::{
        queries::create_post,
        types::{Post, PostCreateData, Visibility},
    },
    profiles::types::DbActorProfile,
    relationships::queries::has_local_followers,
    users::queries::get_user_by_name,
};
use mitra_utils::{
    html::clean_html,
    urls::get_hostname,
};

use crate::activitypub::{
    constants::{AP_MEDIA_TYPE, AP_PUBLIC, AS_MEDIA_TYPE},
    fetcher::fetchers::{fetch_file, FetchError},
    fetcher::helpers::{
        get_or_import_profile_by_actor_address,
        get_or_import_profile_by_actor_id,
        get_post_by_object_id,
        import_post,
    },
    identifiers::{parse_local_actor_id, profile_actor_id},
    receiver::{parse_array, parse_property_value, HandlerError},
    types::{Attachment, EmojiTag, Link, LinkTag, Object, Tag},
    vocabulary::*,
};
use crate::errors::ValidationError;
use crate::media::MediaStorage;
use crate::validators::{
    emojis::{
        validate_emoji_name,
        EMOJI_MEDIA_TYPES,
    },
    posts::{
        content_allowed_classes,
        ATTACHMENT_LIMIT,
        CONTENT_MAX_SIZE,
        EMOJI_LIMIT,
        LINK_LIMIT,
        MENTION_LIMIT,
        OBJECT_ID_SIZE_MAX,
    },
    tags::validate_hashtag,
};
use crate::webfinger::types::ActorAddress;
use super::HandlerResult;

fn get_object_attributed_to(object: &Object)
    -> Result<String, ValidationError>
{
    let attributed_to = object.attributed_to.as_ref()
        .ok_or(ValidationError("unattributed note"))?;
    let author_id = parse_array(attributed_to)
        .map_err(|_| ValidationError("invalid attributedTo property"))?
        .get(0)
        .ok_or(ValidationError("invalid attributedTo property"))?
        .to_string();
    Ok(author_id)
}

pub fn get_object_url(object: &Object) -> Result<String, ValidationError> {
    let maybe_object_url = match &object.url {
        Some(JsonValue::String(string)) => Some(string.to_owned()),
        Some(other_value) => {
            let links: Vec<Link> = parse_property_value(other_value)
                .map_err(|_| ValidationError("invalid object URL"))?;
            links.get(0).map(|link| link.href.clone())
        },
        None => None,
    };
    let object_url = maybe_object_url.unwrap_or(object.id.clone());
    Ok(object_url)
}

pub fn get_object_content(object: &Object) -> Result<String, ValidationError> {
    let content = if let Some(ref content) = object.content {
        if object.media_type == Some("text/markdown".to_string()) {
            format!("<p>{}</p>", content)
        } else {
            // HTML
            content.to_string()
        }
    } else {
        // Lemmy pages and PeerTube videos have "name" property
        object.name.as_deref().unwrap_or("").to_string()
    };
    if content.len() > CONTENT_MAX_SIZE {
        return Err(ValidationError("content is too long"));
    };
    let content_safe = clean_html(&content, content_allowed_classes());
    Ok(content_safe)
}

pub fn create_content_link(url: String) -> String {
    format!(
        r#"<p><a href="{0}" rel="noopener">{0}</a></p>"#,
        url,
    )
}

fn is_gnu_social_link(author_id: &str, attachment: &Attachment) -> bool {
    if !author_id.contains("/index.php/user/") {
        return false;
    };
    if attachment.attachment_type != DOCUMENT {
        return false;
    };
    match attachment.media_type.as_ref() {
        None => true,
        Some(media_type) if media_type.contains("text/html") => true,
        _ => false,
    }
}

pub async fn get_object_attachments(
    db_client: &impl DatabaseClient,
    instance: &Instance,
    storage: &MediaStorage,
    object: &Object,
    author: &DbActorProfile,
) -> Result<(Vec<Uuid>, Vec<String>), HandlerError> {
    let mut attachments = vec![];
    let mut unprocessed = vec![];
    if let Some(ref value) = object.attachment {
        let list: Vec<Attachment> = parse_property_value(value)
            .map_err(|_| ValidationError("invalid attachment property"))?;
        let mut downloaded = vec![];
        for attachment in list {
            match attachment.attachment_type.as_str() {
                DOCUMENT | IMAGE | VIDEO => (),
                _ => {
                    log::warn!(
                        "skipping attachment of type {}",
                        attachment.attachment_type,
                    );
                    continue;
                },
            };
            if is_gnu_social_link(
                &profile_actor_id(&instance.url(), author),
                &attachment,
            ) {
                // Don't fetch HTML pages attached by GNU Social
                continue;
            };
            let attachment_url = attachment.url
                .ok_or(ValidationError("attachment URL is missing"))?;
            let (file_name, file_size, maybe_media_type) = match fetch_file(
                instance,
                &attachment_url,
                attachment.media_type.as_deref(),
                storage.file_size_limit,
                &storage.media_dir,
            ).await {
                Ok(file) => file,
                Err(FetchError::FileTooLarge) => {
                    log::warn!("attachment is too large: {}", attachment_url);
                    unprocessed.push(attachment_url);
                    continue;
                },
                Err(other_error) => {
                    log::warn!("{}", other_error);
                    return Err(ValidationError("failed to fetch attachment").into());
                },
            };
            log::info!("downloaded attachment {}", attachment_url);
            downloaded.push((file_name, file_size, maybe_media_type));
            // Stop downloading if limit is reached
            if downloaded.len() >= ATTACHMENT_LIMIT {
                log::warn!("too many attachments");
                break;
            };
        };
        for (file_name, file_size, maybe_media_type) in downloaded {
            let db_attachment = create_attachment(
                db_client,
                &author.id,
                file_name,
                file_size,
                maybe_media_type,
            ).await?;
            attachments.push(db_attachment.id);
        };
    };
    Ok((attachments, unprocessed))
}

fn normalize_hashtag(tag: &str) -> Result<String, ValidationError> {
    let tag_name = tag.trim_start_matches('#');
    validate_hashtag(tag_name)?;
    Ok(tag_name.to_lowercase())
}

pub fn get_object_links(
    object: &Object,
) -> Vec<String> {
    let mut links = vec![];
    for tag_value in object.tag.clone() {
        let tag_type = tag_value["type"].as_str().unwrap_or(HASHTAG);
        if tag_type == LINK {
            let tag: LinkTag = match serde_json::from_value(tag_value) {
                Ok(tag) => tag,
                Err(_) => {
                    log::warn!("invalid link tag");
                    continue;
                },
            };
            if tag.media_type != AP_MEDIA_TYPE &&
                tag.media_type != AS_MEDIA_TYPE
            {
                // Unknown media type
                continue;
            };
            if !links.contains(&tag.href) {
                links.push(tag.href);
            };
        };
    };
    if let Some(ref object_id) = object.quote_url {
        if !links.contains(object_id) {
            links.push(object_id.to_owned());
        };
    };
    links
}

pub async fn handle_emoji(
    db_client: &impl DatabaseClient,
    instance: &Instance,
    storage: &MediaStorage,
    tag_value: JsonValue,
) -> Result<Option<DbEmoji>, HandlerError> {
    let tag: EmojiTag = match serde_json::from_value(tag_value) {
        Ok(tag) => tag,
        Err(error) => {
            log::warn!("invalid emoji tag: {}", error);
            return Ok(None);
        },
    };
    let emoji_name = tag.name.trim_matches(':');
    if validate_emoji_name(emoji_name).is_err() {
        log::warn!("invalid emoji name: {}", emoji_name);
        return Ok(None);
    };
    let maybe_emoji_id = match get_emoji_by_remote_object_id(
        db_client,
        &tag.id,
    ).await {
        Ok(emoji) => {
            if emoji.updated_at >= tag.updated {
                // Emoji already exists and is up to date
                return Ok(Some(emoji));
            };
            if emoji.emoji_name != emoji_name {
                log::warn!("emoji name can't be changed");
                return Ok(None);
            };
            Some(emoji.id)
        },
        Err(DatabaseError::NotFound("emoji")) => None,
        Err(other_error) => return Err(other_error.into()),
    };
    let (file_name, file_size, maybe_media_type) = match fetch_file(
        instance,
        &tag.icon.url,
        tag.icon.media_type.as_deref(),
        storage.emoji_size_limit,
        &storage.media_dir,
    ).await {
        Ok(file) => file,
        Err(error) => {
            log::warn!("failed to fetch emoji: {}", error);
            return Ok(None);
        },
    };
    let media_type = match maybe_media_type {
        Some(media_type) if EMOJI_MEDIA_TYPES.contains(&media_type.as_str()) => {
            media_type
        },
        _ => {
            log::warn!(
                "unexpected emoji media type: {:?}",
                maybe_media_type,
            );
            return Ok(None);
        },
    };
    log::info!("downloaded emoji {}", tag.icon.url);
    let image = EmojiImage { file_name, file_size, media_type };
    let emoji = if let Some(emoji_id) = maybe_emoji_id {
        update_emoji(
            db_client,
            &emoji_id,
            image,
            &tag.updated,
        ).await?
    } else {
        let hostname = get_hostname(&tag.id)
            .map_err(|_| ValidationError("invalid emoji ID"))?;
        match create_emoji(
            db_client,
            emoji_name,
            Some(&hostname),
            image,
            Some(&tag.id),
            &tag.updated,
        ).await {
            Ok(emoji) => emoji,
            Err(DatabaseError::AlreadyExists(_)) => {
                log::warn!("emoji name is not unique: {}", emoji_name);
                return Ok(None);
            },
            Err(other_error) => return Err(other_error.into()),
        }
    };
    Ok(Some(emoji))
}

pub async fn get_object_tags(
    db_client: &mut impl DatabaseClient,
    instance: &Instance,
    storage: &MediaStorage,
    object: &Object,
    redirects: &HashMap<String, String>,
) -> Result<(Vec<Uuid>, Vec<String>, Vec<Uuid>, Vec<Uuid>), HandlerError> {
    let mut mentions = vec![];
    let mut hashtags = vec![];
    let mut links = vec![];
    let mut emojis = vec![];
    for tag_value in object.tag.clone() {
        let tag_type = tag_value["type"].as_str().unwrap_or(HASHTAG);
        if tag_type == HASHTAG {
            let tag: Tag = match serde_json::from_value(tag_value) {
                Ok(tag) => tag,
                Err(_) => {
                    log::warn!("invalid hashtag");
                    continue;
                },
            };
            if let Some(tag_name) = tag.name {
                // Ignore invalid tags
                if let Ok(tag_name) = normalize_hashtag(&tag_name) {
                    if !hashtags.contains(&tag_name) {
                        hashtags.push(tag_name);
                    };
                };
            };
        } else if tag_type == MENTION {
            if mentions.len() >= MENTION_LIMIT {
                log::warn!("too many mentions");
                continue;
            };
            let tag: Tag = match serde_json::from_value(tag_value) {
                Ok(tag) => tag,
                Err(_) => {
                    log::warn!("invalid mention");
                    continue;
                },
            };
            // Try to find profile by actor ID.
            if let Some(href) = tag.href {
                if let Ok(username) = parse_local_actor_id(&instance.url(), &href) {
                    let user = get_user_by_name(db_client, &username).await?;
                    if !mentions.contains(&user.id) {
                        mentions.push(user.id);
                    };
                    continue;
                };
                // NOTE: `href` attribute is usually actor ID
                // but also can be actor URL (profile link).
                match get_or_import_profile_by_actor_id(
                    db_client,
                    instance,
                    storage,
                    &href,
                ).await {
                    Ok(profile) => {
                        if !mentions.contains(&profile.id) {
                            mentions.push(profile.id);
                        };
                        continue;
                    },
                    Err(error) => {
                        log::warn!(
                            "failed to find mentioned profile by ID {}: {}",
                            href,
                            error,
                        );
                    },
                };
            };
            // Try to find profile by actor address
            let tag_name = match tag.name {
                Some(name) => name,
                None => {
                    log::warn!("failed to parse mention");
                    continue;
                },
            };
            if let Ok(actor_address) = ActorAddress::from_mention(&tag_name) {
                let profile = match get_or_import_profile_by_actor_address(
                    db_client,
                    instance,
                    storage,
                    &actor_address,
                ).await {
                    Ok(profile) => profile,
                    Err(error @ (
                        HandlerError::FetchError(_) |
                        HandlerError::DatabaseError(DatabaseError::NotFound(_))
                    )) => {
                        // Ignore mention if fetcher fails
                        // Ignore mention if local address is not valid
                        log::warn!(
                            "failed to find mentioned profile {}: {}",
                            actor_address,
                            error,
                        );
                        continue;
                    },
                    Err(other_error) => return Err(other_error),
                };
                if !mentions.contains(&profile.id) {
                    mentions.push(profile.id);
                };
            } else {
                log::warn!("failed to parse mention {}", tag_name);
            };
        } else if tag_type == LINK {
            if links.len() >= LINK_LIMIT {
                log::warn!("too many links");
                continue;
            };
            let tag: LinkTag = match serde_json::from_value(tag_value) {
                Ok(tag) => tag,
                Err(_) => {
                    log::warn!("invalid link tag");
                    continue;
                },
            };
            if tag.media_type != AP_MEDIA_TYPE &&
                tag.media_type != AS_MEDIA_TYPE
            {
                // Unknown media type
                continue;
            };
            let href = redirects.get(&tag.href).unwrap_or(&tag.href);
            let linked = get_post_by_object_id(
                db_client,
                &instance.url(),
                href,
            ).await?;
            if !links.contains(&linked.id) {
                links.push(linked.id);
            };
        } else if tag_type == EMOJI {
            if emojis.len() >= EMOJI_LIMIT {
                log::warn!("too many emojis");
                continue;
            };
            match handle_emoji(
                db_client,
                instance,
                storage,
                tag_value,
            ).await? {
                Some(emoji) => {
                    if !emojis.contains(&emoji.id) {
                        emojis.push(emoji.id);
                    };
                },
                None => continue,
            };
        } else {
            log::warn!("skipping tag of type {}", tag_type);
        };
    };
    if let Some(ref object_id) = object.quote_url {
        let object_id = redirects.get(object_id).unwrap_or(object_id);
        let linked = get_post_by_object_id(
            db_client,
            &instance.url(),
            object_id,
        ).await?;
        if !links.contains(&linked.id) {
            links.push(linked.id);
        };
    };
    Ok((mentions, hashtags, links, emojis))
}

fn get_audience(object: &Object) -> Result<Vec<String>, ValidationError> {
    let primary_audience = match object.to {
        Some(ref value) => {
            parse_array(value)
                .map_err(|_| ValidationError("invalid 'to' property value"))?
        },
        None => vec![],
    };
    let secondary_audience = match object.cc {
        Some(ref value) => {
            parse_array(value)
                .map_err(|_| ValidationError("invalid 'cc' property value"))?
        },
        None => vec![],
    };
    let audience = [primary_audience, secondary_audience].concat();
    Ok(audience)
}

fn is_public_object(audience: &[String]) -> bool {
    // Some servers (e.g. Takahe) use "as" namespace
    const PUBLIC_VARIANTS: [&str; 3] = [
        AP_PUBLIC,
        "as:Public",
        "Public",
    ];
    audience.iter().any(|item| PUBLIC_VARIANTS.contains(&item.as_str()))
}

fn get_object_visibility(
    author: &DbActorProfile,
    audience: &[String],
) -> Visibility {
    if is_public_object(audience) {
       return Visibility::Public;
    };
    let actor = author.actor_json.as_ref()
        .expect("actor data should be present");
    if let Some(ref followers) = actor.followers {
        if audience.contains(followers) {
            return Visibility::Followers;
        };
    };
    if let Some(ref subscribers) = actor.subscribers {
        if audience.contains(subscribers) {
            return Visibility::Subscribers;
        };
    };
    Visibility::Direct
}

pub async fn handle_note(
    db_client: &mut impl DatabaseClient,
    instance: &Instance,
    storage: &MediaStorage,
    object: Object,
    redirects: &HashMap<String, String>,
) -> Result<Post, HandlerError> {
    match object.object_type.as_str() {
        NOTE => (),
        ARTICLE | EVENT | QUESTION | PAGE | VIDEO => {
            log::info!("processing object of type {}", object.object_type);
        },
        other_type => {
            log::warn!("discarding object of type {}", other_type);
            return Err(ValidationError("unsupported object type").into());
        },
    };
    if object.id.len() > OBJECT_ID_SIZE_MAX {
        return Err(ValidationError("object ID is too long").into());
    };

    let author_id = get_object_attributed_to(&object)?;
    let author = get_or_import_profile_by_actor_id(
        db_client,
        instance,
        storage,
        &author_id,
    ).await.map_err(|err| {
        log::warn!("failed to import {} ({})", author_id, err);
        err
    })?;

    let mut content = get_object_content(&object)?;
    if object.object_type != NOTE {
        // Append link to object
        let object_url = get_object_url(&object)?;
        content += &create_content_link(object_url);
    };
    let (attachments, unprocessed) = get_object_attachments(
        db_client,
        instance,
        storage,
        &object,
        &author,
    ).await?;
    for attachment_url in unprocessed {
        content += &create_content_link(attachment_url);
    };
    if content.is_empty() && attachments.is_empty() {
        return Err(ValidationError("post is empty").into());
    };

    let (mentions, hashtags, links, emojis) = get_object_tags(
        db_client,
        instance,
        storage,
        &object,
        redirects,
    ).await?;

    let in_reply_to_id = match object.in_reply_to {
        Some(ref object_id) => {
            let object_id = redirects.get(object_id).unwrap_or(object_id);
            let in_reply_to = get_post_by_object_id(
                db_client,
                &instance.url(),
                object_id,
            ).await?;
            Some(in_reply_to.id)
        },
        None => None,
    };
    let audience = get_audience(&object)?;
    let visibility = get_object_visibility(&author, &audience);
    if visibility != Visibility::Public {
        log::warn!(
            "processing note with visibility {:?} attributed to {}",
            visibility,
            author.username,
        );
    };
    let is_sensitive = object.sensitive.unwrap_or(false);
    let created_at = object.published.unwrap_or(Utc::now());
    let post_data = PostCreateData {
        content: content,
        in_reply_to_id,
        repost_of_id: None,
        visibility,
        is_sensitive,
        attachments: attachments,
        mentions: mentions,
        tags: hashtags,
        links: links,
        emojis: emojis,
        object_id: Some(object.id),
        created_at,
    };
    let post = create_post(db_client, &author.id, post_data).await?;
    Ok(post)
}

pub async fn is_unsolicited_message(
    db_client: &impl DatabaseClient,
    instance_url: &str,
    object: &Object,
) -> Result<bool, HandlerError> {
    let author_id = get_object_attributed_to(object)?;
    let author_has_followers =
        has_local_followers(db_client, &author_id).await?;
    let audience = get_audience(object)?;
    let has_local_recipients = audience.iter().any(|actor_id| {
        parse_local_actor_id(instance_url, actor_id).is_ok()
    });
    let result =
        object.in_reply_to.is_none() &&
        is_public_object(&audience) &&
        !has_local_recipients &&
        !author_has_followers;
    Ok(result)
}

#[derive(Deserialize)]
pub struct CreateNote {
    pub actor: String,
    pub object: Object,
}

pub async fn handle_create(
    config: &Config,
    db_client: &mut impl DatabaseClient,
    activity: JsonValue,
    mut is_authenticated: bool,
) -> HandlerResult {
    let activity: CreateNote = serde_json::from_value(activity)
        .map_err(|_| ValidationError("invalid object"))?;
    let object = activity.object;

    // Verify attribution
    let author_id = get_object_attributed_to(&object)?;
    if author_id != activity.actor {
        log::warn!("attributedTo value doesn't match actor");
        is_authenticated = false; // Object will be fetched
    };

    let object_id = object.id.clone();
    let object_received = if is_authenticated {
        Some(object)
    } else {
        // Fetch object, don't trust the sender.
        // Most likely it's a forwarded reply.
        None
    };
    import_post(
        db_client,
        &config.instance(),
        &MediaStorage::from(config),
        object_id,
        object_received,
    ).await?;
    Ok(Some(NOTE))
}

#[cfg(test)]
mod tests {
    use serde_json::json;
    use mitra_models::profiles::types::DbActor;
    use crate::activitypub::{
        types::Object,
        vocabulary::NOTE,
    };
    use super::*;

    #[test]
    fn test_get_object_attributed_to() {
       let object = Object {
            object_type: NOTE.to_string(),
            attributed_to: Some(json!(["https://example.org/1"])),
            ..Default::default()
        };
        let author_id = get_object_attributed_to(&object).unwrap();
        assert_eq!(author_id, "https://example.org/1");
    }

    #[test]
    fn test_get_object_content() {
        let object = Object {
            content: Some("test".to_string()),
            object_type: NOTE.to_string(),
            ..Default::default()
        };
        let content = get_object_content(&object).unwrap();
        assert_eq!(content, "test");
    }

    #[test]
    fn test_get_object_content_from_video() {
        let object = Object {
            name: Some("test-name".to_string()),
            content: Some("test-content".to_string()),
            object_type: "Video".to_string(),
            url: Some(json!([{
                "type": "Link",
                "mediaType": "text/html",
                "href": "https://example.org/xyz",
            }])),
            ..Default::default()
        };
        let mut content = get_object_content(&object).unwrap();
        let object_url = get_object_url(&object).unwrap();
        content += &create_content_link(object_url);
        assert_eq!(
            content,
            r#"test-content<p><a href="https://example.org/xyz" rel="noopener">https://example.org/xyz</a></p>"#,
        );
    }

    #[test]
    fn test_normalize_hashtag() {
        let tag = "#ActivityPub";
        let output = normalize_hashtag(tag).unwrap();

        assert_eq!(output, "activitypub");
    }

    #[test]
    fn test_get_object_visibility_public() {
        let author = DbActorProfile::default();
        let audience = vec![AP_PUBLIC.to_string()];
        let visibility = get_object_visibility(&author, &audience);
        assert_eq!(visibility, Visibility::Public);
    }

    #[test]
    fn test_get_object_visibility_followers() {
        let author_followers = "https://example.com/users/author/followers";
        let author = DbActorProfile {
            actor_json: Some(DbActor {
                followers: Some(author_followers.to_string()),
                ..Default::default()
            }),
            ..Default::default()
        };
        let audience = vec![author_followers.to_string()];
        let visibility = get_object_visibility(&author, &audience);
        assert_eq!(visibility, Visibility::Followers);
    }

    #[test]
    fn test_get_object_visibility_subscribers() {
        let author_followers = "https://example.com/users/author/followers";
        let author_subscribers = "https://example.com/users/author/subscribers";
        let author = DbActorProfile {
            actor_json: Some(DbActor {
                followers: Some(author_followers.to_string()),
                subscribers: Some(author_subscribers.to_string()),
                ..Default::default()
            }),
            ..Default::default()
        };
        let audience = vec![author_subscribers.to_string()];
        let visibility = get_object_visibility(&author, &audience);
        assert_eq!(visibility, Visibility::Subscribers);
    }

    #[test]
    fn test_get_object_visibility_direct() {
        let author = DbActorProfile {
            actor_json: Some(DbActor::default()),
            ..Default::default()
        };
        let audience = vec!["https://example.com/users/1".to_string()];
        let visibility = get_object_visibility(&author, &audience);
        assert_eq!(visibility, Visibility::Direct);
    }
}