mprobe-diagnostics 0.1.1

//! Defines the `Error` types that this crate uses.

use std::convert::From;
use std::error::Error;
use std::fmt;
use std::fmt::Display;
use std::fmt::Formatter;
use std::io;
use std::num::TryFromIntError;
use std::sync::Arc;

use bson::de;
use bson::document::ValueAccessError;

/// The error type for parsing diagnostic metrics.
///
/// Errors mostly originate from I/O read operations, BSON deserialization,
/// and field value accesses.
#[derive(Debug, Clone)]
pub enum MetricParseError {
    /// A [std::io::Error] encountered while reading diagnostic metrics.
    Io(Arc<io::Error>),

    /// A [bson::de::Error] encountered while deserializing BSON documents.
    BsonDeserialzation(de::Error),

    /// A [KeyAccessError] encountered while accessing BSON fields.
    FieldAccess(KeyAccessError),

    /// Unknown BSON document read from the diagnostic metrics.
    UnknownDocumentKind(i32),

    /// The amount of metrics in the reference document is different
    /// than the amount of metric samples.
    MetricCountMismatch,

    /// The timestamp for the given metric is missing.
    MetricTimestampNotFound {
        /// Metric name
        name: Arc<str>,
    },

    /// A [TryFromIntError] encountered while converting integer values from [i32] to
    /// [usize].
    IntConversion(TryFromIntError),
}

impl Display for MetricParseError {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        let parse_error = "metric parse error:";

        match self {
            MetricParseError::Io(error) => write!(f, "{parse_error} I/O error: {error}"),
            MetricParseError::BsonDeserialzation(error) => {
                write!(f, "{parse_error} BSON deserialization error: {error}")
            }
            MetricParseError::FieldAccess(error) => write!(
                f,
                "{parse_error} could not read the document field: {error}"
            ),
            MetricParseError::MetricCountMismatch => write!(
                f,
                "{parse_error} the amount of metrics in the reference document is different than the amount of metric samples"
            ),
            MetricParseError::MetricTimestampNotFound { name } => write!(
                f,
                "{parse_error} the metric timestamps for the {name} metric could not be found",
            ),
            MetricParseError::IntConversion(error) => {
                write!(f, "{parse_error} could not parse integer: {error}")
            }
            MetricParseError::UnknownDocumentKind(value) => {
                write!(f, "{parse_error} unknonw document type: {value}")
            }
        }
    }
}

impl Error for MetricParseError {
    fn source(&self) -> Option<&(dyn Error + 'static)> {
        match self {
            MetricParseError::Io(error) => Some(error),
            MetricParseError::BsonDeserialzation(error) => Some(error),
            MetricParseError::FieldAccess(error) => Some(error),
            MetricParseError::MetricCountMismatch => None,
            MetricParseError::MetricTimestampNotFound { .. } => None,
            MetricParseError::IntConversion(error) => Some(error),
            MetricParseError::UnknownDocumentKind(_) => None,
        }
    }
}

impl From<io::Error> for MetricParseError {
    fn from(error: io::Error) -> Self {
        MetricParseError::Io(Arc::new(error))
    }
}

impl From<de::Error> for MetricParseError {
    fn from(error: de::Error) -> Self {
        MetricParseError::BsonDeserialzation(error)
    }
}

impl From<TryFromIntError> for MetricParseError {
    fn from(error: TryFromIntError) -> Self {
        MetricParseError::IntConversion(error)
    }
}

impl From<KeyAccessError> for MetricParseError {
    fn from(error: KeyAccessError) -> Self {
        MetricParseError::FieldAccess(error)
    }
}

/// The error type for accessing BSON fields.
#[derive(Debug, Clone)]
pub enum KeyAccessError {
    /// Could not find the field with the specified key.
    KeyNotFound {
        /// Key field name.
        key: String,
    },

    /// The field with the specified key was found, but not with the expected type.
    UnexpectedKeyType {
        /// Key field name.
        key: String,
    },

    /// Could not access field value with the specified key due to an unknown error.
    AccessError {
        /// Key field name.
        key: String,

        /// Underlying error message.
        error: String,
    },
}

impl Display for KeyAccessError {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        let key_access_error = "key access error:";
        match *self {
            KeyAccessError::KeyNotFound { ref key } => {
                write!(
                    f,
                    "{key_access_error} could not find the field with the {key} key",
                )
            }
            KeyAccessError::UnexpectedKeyType { ref key } => write!(
                f,
                "{key_access_error} the field with {key} key was found, but not with the expected type",
            ),
            KeyAccessError::AccessError { ref key, ref error } => {
                write!(
                    f,
                    "{key_access_error} could not access the field value with the {key} key. {error}",
                )
            }
        }
    }
}

impl Error for KeyAccessError {}

pub(crate) trait ValueAccessResultExt<T> {
    fn map_value_access_err(self, key: &str) -> Result<T, KeyAccessError>;
}

impl<T> ValueAccessResultExt<T> for Result<T, ValueAccessError> {
    fn map_value_access_err(self, key: &str) -> Result<T, KeyAccessError> {
        self.map_err(|error| match error {
            ValueAccessError::NotPresent => KeyAccessError::KeyNotFound {
                key: key.to_owned(),
            },
            ValueAccessError::UnexpectedType => KeyAccessError::UnexpectedKeyType {
                key: key.to_owned(),
            },
            e => KeyAccessError::AccessError {
                key: key.to_owned(),
                error: e.to_string(),
            },
        })
    }
}