use base64::{engine::general_purpose::URL_SAFE as base64url, Engine};
use serde::{Serialize, Deserialize};
use tetratto_shared::hash::hash;
use super::{Result, Error};

#[derive(Clone, Debug, Serialize, Deserialize)]
pub struct AuthGrant {
    pub id: usize,
    /// The name of the application associated with this grant.
    pub name: String,
    /// The code challenge for PKCE verifiers associated with this grant.
    ///
    /// This challenge is *all* that is required to refresh this grant's auth token.
    /// While there can only be one token at a time, it can be refreshed whenever as long
    /// as the provided verifier matches that of the challenge.
    ///
    /// The challenge should never be changed. To change the challenge, the grant
    /// should be removed and recreated.
    pub challenge: String,
    /// The encoding method for the initial verifier in the challenge.
    pub method: PkceChallengeMethod,
    /// The access token associated with the account. This is **not** the same as
    /// regular account access tokens, as the token can only be used with the requested `scopes`.
    pub token: String,
    /// Scopes define what the grant's token is actually allowed to do.
    ///
    /// No scope shall ever be allowed to change scopes or manage grants on behalf of the user.
    /// A regular user token **must** be provided to manage grants.
    pub scopes: Vec<AppScope>,
}

#[derive(Clone, Debug, Serialize, Deserialize, PartialEq, Eq)]
pub enum PkceChallengeMethod {
    S256,
}

#[derive(Clone, Debug, Serialize, Deserialize, PartialEq, Eq)]
pub enum AppScope {
    /// Read the profile of other user's on behalf of the user.
    UserReadProfiles,
    /// Read the user's profile (username, bio, etc).
    UserReadProfile,
    /// Read the user's settings.
    UserReadSettings,
    /// Read the user's sessions and info.
    UserReadSessions,
    /// Read posts as the user.
    UserReadPosts,
    /// Read messages as the user.
    UserReadMessages,
    /// Read drafts as the user.
    UserReadDrafts,
    /// Read the user's communities.
    UserReadCommunities,
    /// Connect to sockets on the user's behalf.
    UserReadSockets,
    /// Read the user's notifications.
    UserReadNotifications,
    /// Read the user's requests.
    UserReadRequests,
    /// Read questions as the user.
    UserReadQuestions,
    /// Create posts as the user.
    UserCreatePosts,
    /// Create messages as the user.
    UserCreateMessages,
    /// Ask questions as the user.
    UserCreateQuestions,
    /// Create IP blocks as the user.
    UserCreateIpBlock,
    /// Create drafts on behalf of the user.
    UserCreateDrafts,
    /// Create communities on behalf of the user.
    UserCreateCommunities,
    /// Create stacks on behalf of the user.
    UserCreateStacks,
    /// Delete posts owned by the user.
    UserDeletePosts,
    /// Delete messages owned by the user.
    UserDeleteMessages,
    /// Delete questions as the user.
    UserDeleteQuestions,
    /// Delete drafts as the user.
    UserDeleteDrafts,
    /// Edit the user's settings and upload avatars/banners on behalf of the user.
    UserManageProfile,
    /// Manage stacks owned by the user.
    UserManageStacks,
    /// Manage the user's following/unfollowing.
    UserManageRelationships,
    /// Manage the user's community memberships.
    ///
    /// Also includes managing the membership of users in the user's communities.
    UserManageMemberships,
    /// Follow/unfollow users on behalf of the user.
    UserManageFollowing,
    /// Accept follow requests on behalf of the user.
    UserManageFollowers,
    /// Block/unblock users on behalf of the user.
    UserManageBlocks,
    /// Manage the user's notifications.
    UserManageNotifications,
    /// Manage the user's requests.
    UserManageRequests,
    /// Manage the user's uploads.
    UserManageUploads,
    /// Edit posts created by the user.
    UserEditPosts,
    /// Edit drafts created by the user.
    UserEditDrafts,
    /// Vote in polls as the user.
    UserVote,
    /// React to posts on behalf of the user. Also allows the removal of reactions.
    UserReact,
    /// Join communities on behalf of the user.
    UserJoinCommunities,
    /// Permanently delete posts.
    ModPurgePosts,
    /// Restore deleted posts.
    ModDeletePosts,
    /// Manage user warnings.
    ModManageWarnings,
    /// Get a list of all emojis available to the user.
    UserReadEmojis,
    /// Create emojis on behalf of the user.
    CommunityCreateEmojis,
    /// Manage emojis on behalf of the user.
    CommunityManageEmojis,
    /// Delete communities on behalf of the user.
    CommunityDelete,
    /// Manage communities on behalf of the user.
    CommunityManage,
    /// Transfer ownership of communities on behalf of the user.
    CommunityTransferOwnership,
    /// Read the membership of users in communities owned by the current user.
    CommunityReadMemberships,
    /// Create channels in the user's communities.
    CommunityCreateChannels,
    /// Manage channels in the user's communities.
    CommunityManageChannels,
}

impl AppScope {
    /// Parse the given input string as a list of scopes.
    pub fn parse(input: &str) -> Vec<AppScope> {
        let mut out: Vec<AppScope> = Vec::new();
        for scope in input.split(" ") {
            out.push(match scope {
                "user-read-profiles" => Self::UserReadProfiles,
                "user-read-profile" => Self::UserReadProfile,
                "user-read-settings" => Self::UserReadSettings,
                "user-read-sessions" => Self::UserReadSessions,
                "user-read-posts" => Self::UserReadPosts,
                "user-read-messages" => Self::UserReadMessages,
                "user-read-drafts" => Self::UserReadDrafts,
                "user-read-communities" => Self::UserReadCommunities,
                "user-read-sockets" => Self::UserReadSockets,
                "user-read-notifications" => Self::UserReadNotifications,
                "user-read-requests" => Self::UserReadRequests,
                "user-read-questions" => Self::UserReadQuestions,
                "user-create-posts" => Self::UserCreatePosts,
                "user-create-messages" => Self::UserCreateMessages,
                "user-create-questions" => Self::UserCreateQuestions,
                "user-create-ip-blocks" => Self::UserCreateIpBlock,
                "user-create-drafts" => Self::UserCreateDrafts,
                "user-create-communities" => Self::UserCreateCommunities,
                "user-delete-posts" => Self::UserDeletePosts,
                "user-delete-messages" => Self::UserDeleteMessages,
                "user-delete-questions" => Self::UserDeleteQuestions,
                "user-delete-drafts" => Self::UserDeleteDrafts,
                "user-manage-profile" => Self::UserManageProfile,
                "user-manage-stacks" => Self::UserManageStacks,
                "user-manage-relationships" => Self::UserManageRelationships,
                "user-manage-memberships" => Self::UserManageMemberships,
                "user-manage-following" => Self::UserManageFollowing,
                "user-manage-followers" => Self::UserManageFollowers,
                "user-manage-blocks" => Self::UserManageBlocks,
                "user-manage-notifications" => Self::UserManageNotifications,
                "user-manage-requests" => Self::UserManageRequests,
                "user-manage-uploads" => Self::UserManageUploads,
                "user-edit-posts" => Self::UserEditPosts,
                "user-edit-drafts" => Self::UserEditDrafts,
                "user-vote" => Self::UserVote,
                "user-react" => Self::UserReact,
                "user-join-communities" => Self::UserJoinCommunities,
                "mod-purge-posts" => Self::ModPurgePosts,
                "mod-delete-posts" => Self::ModDeletePosts,
                "mod-manage-warnings" => Self::ModManageWarnings,
                "user-read-emojis" => Self::UserReadEmojis,
                "community-create-emojis" => Self::CommunityCreateEmojis,
                "community-manage-emojis" => Self::CommunityManageEmojis,
                "community-delete" => Self::CommunityDelete,
                "community-manage" => Self::CommunityManage,
                "community-transfer-ownership" => Self::CommunityTransferOwnership,
                "community-read-memberships" => Self::CommunityReadMemberships,
                "community-create-channels" => Self::CommunityCreateChannels,
                "community-manage-channels" => Self::CommunityManageChannels,
                _ => continue,
            })
        }
        out
    }
}

impl AuthGrant {
    /// Check a verifier against the stored challenge (using the given [`PkceChallengeMethod`]).
    pub fn check_verifier(&self, verifier: &str) -> Result<()> {
        if self.method != PkceChallengeMethod::S256 {
            return Err(Error::MiscError("only S256 is supported".to_string()));
        }

        let decoded = match base64url.decode(self.challenge.as_bytes()) {
            Ok(hash) => hash,
            Err(e) => return Err(Error::MiscError(e.to_string())),
        };

        let hash = hash(verifier.to_string());

        if hash.as_bytes() != decoded {
            // the verifier we received does not match the verifier from the stored challenge
            return Err(Error::NotAllowed);
        }

        Ok(())
    }
}