use serde::{Serialize, Deserialize};
use url::Url;

mod scopes;
pub use self::scopes::{Scope, Scopes};
mod pkce;
pub use self::pkce::{PKCEMethod, PKCEVerifier, PKCEChallenge};

#[derive(Copy, Clone, Debug, Serialize, Deserialize)]
pub enum IntrospectionEndpointAuthMethod {
    Bearer,
    #[serde(rename = "snake_case")]
    ClientSecretPost,
    #[serde(rename = "snake_case")]
    ClientSecretBasic,
    #[serde(rename = "snake_case")]
    TlsClientAuth,
    #[serde(rename = "snake_case")]
    SelfSignedTlsClientAuth
}

#[derive(Copy, Clone, Debug, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum RevocationEndpointAuthMethod {
    None
}

#[derive(Copy, Clone, Debug, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum ResponseType {
    Code
}

#[derive(Copy, Clone, Debug, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum GrantType {
    AuthorizationCode,
    RefreshToken
}

/// OAuth 2.0 Authorization Server Metadata in application to the IndieAuth protocol.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Metadata {
    /// The server's issuer identifier. The issuer identifier is a URL
    /// that uses the "https" scheme and has no query or fragment
    /// components. The identifier MUST be a prefix of the
    /// `indieauth-metadata` URL.
    pub issuer: Url,
    /// The Authorization Endpoint
    pub authorization_endpoint: Url,
    /// The Token Endpoint
    pub token_endpoint: Url,
    /// The Introspection Endpoint
    pub introspection_endpoint: Url,
    /// JSON array containing a list of client authentication methods supported by this introspection endpoint.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub introspection_endpoint_auth_methods_supported: Option<Vec<IntrospectionEndpointAuthMethod>>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub revocation_endpoint: Option<Url>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub revocation_endpoint_auth_methods_supported: Option<Vec<RevocationEndpointAuthMethod>>,
    // Note: Scopes isn't used here because this field should be
    // serialized as a list, not as a string
    #[serde(skip_serializing_if = "Option::is_none")]
    pub scopes_supported: Option<Vec<Scope>>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub response_types_supported: Option<Vec<ResponseType>>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub grant_types_supported: Option<Vec<GrantType>>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub service_documentation: Option<Url>,
    pub code_challenge_methods_supported: Vec<PKCEMethod>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub authorization_response_iss_parameter_supported: Option<bool>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub userinfo_endpoint: Option<Url>
}

#[derive(Clone, Debug, Serialize, Deserialize)]
pub struct Profile {
    pub name: String,
    pub url: Url,
    pub photo: Url,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub email: Option<String>
}

#[derive(Clone, Debug, PartialEq, Eq, Deserialize, Serialize)]
pub struct State(String);
impl State {
    fn new() -> Self {
        use rand::{Rng, distributions::Alphanumeric};
        let bytes = rand::thread_rng()
            .sample_iter(&Alphanumeric)
            .take(128)
            .collect::<Vec<u8>>();
        Self(String::from_utf8(bytes).unwrap())
    }
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct AuthorizationRequest {
    pub response_type: ResponseType,
    pub client_id: Url,
    pub redirect_uri: Url,
    pub state: State,
    #[serde(flatten)]
    pub code_challenge: PKCEChallenge,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub scope: Option<Scopes>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub me: Option<Url>
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct AuthorizationResponse {
    pub code: String,
    pub state: State,
    pub iss: Url
}

#[derive(PartialEq, Debug, Clone, Serialize, Deserialize)]
#[serde(tag = "grant_type")]
#[serde(rename_all = "snake_case")]
pub enum GrantRequest {
    AuthorizationCode {
        code: String,
        client_id: Url,
        redirect_uri: Url,
        code_verifier: PKCEVerifier
    },
    RefreshToken {
        refresh_token: String,
        client_id: url::Url,
        scope: Option<Scopes>
    }
}

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(untagged)]
pub enum GrantResponse {
    AccessToken {
        me: Url,
        #[serde(skip_serializing_if = "Option::is_none")]
        profile: Option<Profile>,
        access_token: String,
        #[serde(skip_serializing_if = "Option::is_none")]
        expires_in: Option<u64>,
        #[serde(skip_serializing_if = "Option::is_none")]
        refresh_token: Option<String>
    },
    ProfileUrl {
        me: Url,
        #[serde(skip_serializing_if = "Option::is_none")]
        profile: Option<Profile>
    }
}

/// Describes requests that the authorization endpoint might want to handle.
///
/// This type mostly exists for ease-of-use with serde.
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(untagged)]
pub enum RequestMaybeAuthorizationEndpoint {
    Authorization(AuthorizationRequest),
    Grant(GrantRequest)
}

#[derive(Debug, Serialize, Deserialize)]
pub struct TokenIntrospectionRequest {
    pub token: String
}

#[derive(Debug, Serialize, Deserialize)]
pub struct TokenData {
    pub me: Url,
    pub client_id: Url,
    pub scope: Scopes,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub exp: Option<u64>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub iat: Option<u64>
}

impl TokenData {
    pub fn expired(&self) -> bool {
        use std::time::{Duration, SystemTime, UNIX_EPOCH};
        
        self.exp
            .map(|exp| SystemTime::now()
                 .duration_since(UNIX_EPOCH)
                 .unwrap_or(Duration::ZERO)
                 .as_secs() >= exp)
            .unwrap_or_default()
    }

    pub fn expires_at(&self) -> Option<std::time::SystemTime> {
        self.exp.map(|time| {
            std::time::UNIX_EPOCH + std::time::Duration::from_secs(time)
        })
    }
    
    pub fn issued_at(&self) -> Option<std::time::SystemTime> {
        self.iat.map(|time| {
            std::time::UNIX_EPOCH + std::time::Duration::from_secs(time)
        })
    }
}

// I don't like this type, because it could've been represented
// internally by Option<TokenData>. But the IndieAuth standard
// requires the "active" field to be present. I can't do anything
// about it.
#[derive(Debug, Serialize, Deserialize)]
pub struct TokenIntrospectionResponse {
    active: bool,
    #[serde(flatten)]
    #[serde(skip_serializing_if = "Option::is_none")]
    data: Option<TokenData>
}
// These wrappers and impls should take care of making use of this
// type as painless as possible.
impl TokenIntrospectionResponse {
    pub fn inactive() -> Self {
        Self { active: false, data: None }
    }
    pub fn active(data: TokenData) -> Self {
        Self { active: true, data: Some(data) }
    }

    pub fn is_active(&self) -> bool {
        self.active
    }

    pub fn data(&self) -> Option<&TokenData> {
        if !self.active {
            return None
        }
        self.data.as_ref()
    }
}
impl Default for TokenIntrospectionResponse {
    fn default() -> Self {
        Self::inactive()
    }
}
impl From<Option<TokenData>> for TokenIntrospectionResponse {
    fn from(data: Option<TokenData>) -> Self {
        Self { active: data.is_some(), data }
    }
}
impl From<TokenIntrospectionResponse> for Option<TokenData> {
    fn from(response: TokenIntrospectionResponse) -> Option<TokenData> {
        response.data
    }
}

#[derive(Debug, Serialize, Deserialize)]
pub struct TokenRevocationRequest {
    pub token: String
}

/// Types of errors that a resource server (IndieAuth consumer) can
/// throw when authentication goes wrong.
#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum ResourceErrorKind {
    InvalidRequest,
    InvalidToken,
    InsufficientScope,
}

#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum ErrorKind {
    /// The request is missing a required parameter, includes an
    /// unsupported parameter value (other than grant type), repeats a
    /// parameter, includes multiple credentials, utilizes more than
    /// one mechanism for authenticating the client, or is otherwise
    /// malformed.
    InvalidRequest,
    /// Client authentication failed (e.g., unknown client, no client
    /// authentication included, or unsupported authentication
    /// method).  The authorization server MAY return an HTTP 401
    /// (Unauthorized) status code to indicate which HTTP
    /// authentication schemes are supported.  If the client attempted
    /// to authenticate via the "Authorization" request header field,
    /// the authorization server MUST respond with an HTTP 401
    /// (Unauthorized) status code and include the "WWW-Authenticate"
    /// response header field matching the authentication scheme used
    /// by the client.
    InvalidClient,
    /// The provided authorization grant (e.g., authorization
    /// code, resource owner credentials) or refresh token is
    /// invalid, expired, revoked, does not match the redirection
    /// URI used in the authorization request, or was issued to
    /// another client.
    InvalidGrant,
    /// The authenticated client is not authorized to use this
    /// authorization grant type.
    UnauthorizedClient,
    /// The authorization grant type is not supported by the
    /// authorization server.
    UnsupportedGrantType,
    /// The requested scope is invalid, unknown, malformed, or
    /// exceeds the scope granted by the resource owner.
    InvalidScope
}
// TODO consider relying on serde_variant for these conversions
impl AsRef<str> for ErrorKind {
    fn as_ref(&self) -> &str {
        match self {
            ErrorKind::InvalidRequest => "invalid_request",
            ErrorKind::InvalidClient => "invalid_client",
            ErrorKind::InvalidGrant => "invalid_grant",
            ErrorKind::UnauthorizedClient => "unauthorized_client",
            ErrorKind::UnsupportedGrantType => "unsupported_grant_type",
            ErrorKind::InvalidScope => "invalid_scope",
        }
    }
}
impl std::fmt::Display for ErrorKind {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.as_ref())
    }
}


#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Error {
    #[serde(rename = "error")]
    pub kind: ErrorKind,
    #[serde(rename = "error_description")]
    pub msg: Option<String>,
    pub error_uri: Option<url::Url>
}

impl From<ErrorKind> for Error {
    fn from(kind: ErrorKind) -> Error {
        Error {
            kind, msg: None, error_uri: None
        }
    }
}

impl std::error::Error for self::Error {}

impl std::fmt::Display for self::Error {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "IndieAuth error ({})", self.kind)?;
        if let Some(msg) = self.msg.as_deref() {
            write!(f, ": {}", msg)?;
        }
        if let Some(error_uri) = &self.error_uri {
            write!(f, " (see `{}` for more info)", error_uri)?;
        }

        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_serialize_deserialize_grant_request() {
        let authorization_code: GrantRequest = GrantRequest::AuthorizationCode {
            client_id: "https://kittybox.fireburn.ru/".parse().unwrap(),
            redirect_uri: "https://kittybox.fireburn.ru/.kittybox/login/redirect".parse().unwrap(),
            code_verifier: PKCEVerifier("helloworld".to_string()),
            code: "hithere".to_owned()
        };
        let serialized = serde_urlencoded::to_string(&[
            ("grant_type", "authorization_code"),
            ("code", "hithere"),
            ("client_id", "https://kittybox.fireburn.ru/"),
            ("redirect_uri", "https://kittybox.fireburn.ru/.kittybox/login/redirect"),
            ("code_verifier", "helloworld"),
        ]).unwrap();

        let deserialized = serde_urlencoded::from_str(&serialized).unwrap();

        assert_eq!(authorization_code, deserialized);

        assert_eq!(
            serialized,
            serde_urlencoded::to_string(authorization_code).unwrap()
        )
    }
}