//! All error types that are returned by methods in this crate.
use serde::Deserialize;
use std::error::Error as StdError;
use std::fmt;

/// A global error enum that contains all errors that are returned by this
/// library. Some errors are wrappers for errors from underlying libraries.
/// All errors (this enum as well as all contained structs) implement [`std::error::Error`].
#[non_exhaustive]
#[derive(Debug)]
pub enum Error {
    /// Wraps errors from the underlying [`reqwest::Client`] that cannot be mapped
    /// to a more specific error type. Deserialization errors also fall into this
    /// category.
    Client(ClientError),
    /// Occurs when Prometheus responds with e.g. HTTP 4xx (e.g. due to a syntax error in a PromQL query).<br>
    /// Details on the error as reported by Prometheus are included in [`PrometheusError`].
    Prometheus(PrometheusError),
    /// Occurs when the [`Client::series`](crate::Client::series) method is called with an empty set of
    /// series [`Selector`](crate::selector::Selector)s. According to the Prometheus API description at least one
    /// [`Selector`](crate::selector::Selector) must be provided.
    EmptySeriesSelector,
    /// Wraps errors from the [`url`] crate.
    ParseUrl(ParseUrlError),
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Self::Client(e) => e.fmt(f),
            Self::Prometheus(e) => e.fmt(f),
            Self::EmptySeriesSelector => f.write_str("at least one series selector must be provided in order to query the series endpoint"),
            Self::ParseUrl(e) => e.fmt(f),
        }
    }
}

impl StdError for Error {
    fn source(&self) -> Option<&(dyn StdError + 'static)> {
        match self {
            Self::Client(e) => e.source(),
            Self::Prometheus(_) => None,
            Self::EmptySeriesSelector => None,
            Self::ParseUrl(e) => e.source(),
        }
    }
}

/// This error is thrown when the JSON response's `status` field contains `error`.<br>
/// The error-related information from the JSON body is included in this error.
#[derive(Debug, Clone, PartialEq, Deserialize)]
pub struct PrometheusError {
    #[serde(alias = "errorType")]
    pub(crate) error_type: PrometheusErrorType,
    #[serde(alias = "error")]
    pub(crate) message: String,
}

impl StdError for PrometheusError {}

impl fmt::Display for PrometheusError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}: {}", self.error_type, self.message)
    }
}

impl PrometheusError {
    /// Returns the parsed version of the error type that was given by the Prometheus API.
    pub fn error_type(&self) -> PrometheusErrorType {
        self.error_type
    }

    /// Returns the error message that was given by the Prometheus API.
    pub fn message(&self) -> &str {
        &self.message
    }

    pub fn is_timeout(&self) -> bool {
        self.error_type == PrometheusErrorType::Timeout
    }

    pub fn is_canceled(&self) -> bool {
        self.error_type == PrometheusErrorType::Canceled
    }

    pub fn is_execution(&self) -> bool {
        self.error_type == PrometheusErrorType::Execution
    }

    pub fn is_bad_data(&self) -> bool {
        self.error_type == PrometheusErrorType::BadData
    }

    pub fn is_internal(&self) -> bool {
        self.error_type == PrometheusErrorType::Internal
    }

    pub fn is_unavailable(&self) -> bool {
        self.error_type == PrometheusErrorType::Unavailable
    }

    pub fn is_not_found(&self) -> bool {
        self.error_type == PrometheusErrorType::NotFound
    }
}

/// The parsed error type as returned by the Prometheus API.
#[non_exhaustive]
#[derive(Clone, Copy, Debug, Deserialize, PartialEq)]
pub enum PrometheusErrorType {
    #[serde(alias = "timeout")]
    Timeout,
    #[serde(alias = "canceled")]
    Canceled,
    #[serde(alias = "execution")]
    Execution,
    #[serde(alias = "bad_data")]
    BadData,
    #[serde(alias = "internal")]
    Internal,
    #[serde(alias = "unavailable")]
    Unavailable,
    #[serde(alias = "not_found")]
    NotFound,
}

impl fmt::Display for PrometheusErrorType {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Self::Timeout => f.write_str("timeout"),
            Self::Canceled => f.write_str("canceled"),
            Self::Execution => f.write_str("execution"),
            Self::BadData => f.write_str("bad_data"),
            Self::Internal => f.write_str("internal"),
            Self::Unavailable => f.write_str("unavailable"),
            Self::NotFound => f.write_str("not_found"),
        }
    }
}

/// Is thrown when the [`Client`](crate::Client) or the underlying
/// [`reqwest::Error`] fail to build or execute a request.
#[derive(Debug)]
pub struct ClientError {
    pub(crate) message: &'static str,
    pub(crate) source: Option<reqwest::Error>,
}

impl fmt::Display for ClientError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.write_str(&self.message)
    }
}

impl StdError for ClientError {
    fn source(&self) -> Option<&(dyn StdError + 'static)> {
        self.source.as_ref().map(|e| e as &dyn StdError)
    }
}

impl ClientError {
    /// Obtain the [`reqwest::Error`] that is the actual cause of this
    /// error or `None` if the error originated in [`Client`](crate::Client)
    /// itself.<br>
    pub fn inner(&self) -> Option<&reqwest::Error> {
        self.source.as_ref()
    }
}

/// Is thrown when the URL that is used to instantiate the [`Client`](crate::Client)
/// is invalid.
#[derive(Debug)]
pub struct ParseUrlError {
    pub(crate) message: &'static str,
    pub(crate) source: url::ParseError,
}

impl fmt::Display for ParseUrlError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.write_str(&self.message)
    }
}

impl StdError for ParseUrlError {
    fn source(&self) -> Option<&(dyn StdError + 'static)> {
        Some(&self.source)
    }
}

impl ParseUrlError {
    /// Obtain the [`url::ParseError`] that is the actual cause of this error.
    pub fn inner(&self) -> &url::ParseError {
        &self.source
    }
}