use std::error::Error;

use lettre::address::AddressError;
use poem_openapi::payload::Json;
use validator::ValidationErrors;

use super::ContactResponse;

/// Errors that can occur during contact form processing and email sending.
#[derive(Debug)]
pub enum ContactError {
    /// The email address provided in the contact form request could not be parsed.
    ///
    /// This typically indicates the user submitted an invalid email address format.
    CouldNotParseRequestEmailAddress(String),
    /// The email address configured in application settings could not be parsed.
    ///
    /// This indicates a configuration error with the sender or recipient email addresses.
    CouldNotParseSettingsEmail(String),
    /// Failed to construct the email message.
    ///
    /// This can occur due to invalid message content or headers.
    FailedToBuildMessage(String),
    /// Failed to send the email through the SMTP server.
    ///
    /// This can occur due to network issues, authentication failures, or SMTP server errors.
    CouldNotSendEmail(String),
    /// A general validation error occurred that doesn't fit specific field validation.
    ///
    /// This is used for validation errors that don't map to a specific form field.
    ValidationError(String),
    /// The name field in the contact form failed validation.
    ///
    /// This typically occurs when the name is empty, too short, or contains invalid characters.
    ValidationNameError(String),
    /// The email field in the contact form failed validation.
    ///
    /// This typically occurs when the email address format is invalid.
    ValidationEmailError(String),
    /// The message field in the contact form failed validation.
    ///
    /// This typically occurs when the message is empty, too short.
    ValidationMessageError(String),
    /// An unspecified internal error occurred.
    OtherError(String),
}

impl Error for ContactError {}

/// Converts a lettre SMTP transport error into a `ContactError`.
///
/// SMTP errors are logged at ERROR level with full details, then
/// mapped to `OtherError` as they represent server-side or network
/// issues beyond the client's control.
impl From<lettre::transport::smtp::Error> for ContactError {
    fn from(value: lettre::transport::smtp::Error) -> Self {
        tracing::event!(target: "contact", tracing::Level::ERROR, "SMTP Error details: {}", format!("{value:?}"));
        Self::OtherError(value.to_string())
    }
}

impl std::fmt::Display for ContactError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let message = match self {
            Self::CouldNotParseRequestEmailAddress(e) => {
                format!("Failed to parse requester's email address: {e:?}")
            }
            Self::CouldNotParseSettingsEmail(e) => {
                format!("Failed to parse email address in settings: {e:?}")
            }
            Self::FailedToBuildMessage(e) => {
                format!("Failed to build the message to be sent: {e:?}")
            }
            Self::CouldNotSendEmail(e) => format!("Failed to send the email: {e:?}"),
            Self::ValidationError(e) => format!("Failed to validate request: {e:?}"),
            Self::ValidationNameError(e) => format!("Failed to validate name: {e:?}"),
            Self::ValidationEmailError(e) => format!("Failed to validate email: {e:?}"),
            Self::ValidationMessageError(e) => format!("Failed to validate message: {e:?}"),
            Self::OtherError(e) => format!("Other internal error: {e:?}"),
        };
        write!(f, "{message}")
    }
}

/// Converts validation errors into a `ContactError`.
///
/// This implementation inspects the validation errors to determine which specific field
/// failed validation (name, email, or message) and returns the appropriate variant.
/// If no specific field can be identified, returns a generic `ValidationError`.
impl From<ValidationErrors> for ContactError {
    fn from(value: ValidationErrors) -> Self {
        if validator::ValidationErrors::has_error(&Err(value.clone()), "name") {
            return Self::ValidationNameError("backend.contact.errors.validation.name".to_owned());
        }
        if validator::ValidationErrors::has_error(&Err(value.clone()), "email") {
            return Self::ValidationEmailError("backend.contact.errors.validation.email".to_owned());
        }
        if validator::ValidationErrors::has_error(&Err(value), "message") {
            return Self::ValidationMessageError("backend.contact.errors.validation.message".to_owned());
        }
        Self::ValidationError("backend.contact.errors.validation.other".to_owned())
    }
}

/// Converts a `ContactError` into a `ContactResponse`.
///
/// This maps error variants to user-facing error message keys for internationalization.
/// Validation errors map to specific field error keys, while internal errors
/// (settings, email building, SMTP issues) all map to a generic internal error key.
impl From<ContactError> for ContactResponse {
    fn from(value: ContactError) -> Self {
        Self {
            success: false,
            message: match value {
                ContactError::CouldNotParseRequestEmailAddress(_)
                | ContactError::ValidationEmailError(_) => "backend.contact.errors.validation.email",
                ContactError::ValidationNameError(_) => "backend.contact.errors.validation.name",
                ContactError::ValidationMessageError(_) => "backend.contact.errors.validation.message",
                ContactError::CouldNotParseSettingsEmail(_)
                | ContactError::FailedToBuildMessage(_)
                | ContactError::CouldNotSendEmail(_)
                | ContactError::OtherError(_) => "backend.contact.errors.internal",
                ContactError::ValidationError(_) => "backend.contact.errors.validation.other",
            }
            .to_string(),
        }
    }
}

/// Converts validation errors directly into a `ContactResponse`.
///
/// This is a convenience implementation that first converts `ValidationErrors` to
/// `ContactError`, then converts that to `ContactResponse`. This allows validation
/// errors to be returned directly from handlers as responses.
impl From<ValidationErrors> for ContactResponse {
    fn from(value: ValidationErrors) -> Self {
        let error: ContactError = value.into();
        error.into()
    }
}

/// Converts a lettre `AddressError` into a `ContactError`.
///
/// Address parsing errors from lettre are mapped to `CouldNotParseSettingsEmail`
/// as they typically occur when parsing email addresses from application settings.
impl From<AddressError> for ContactError {
    fn from(value: AddressError) -> Self {
        Self::CouldNotParseSettingsEmail(value.to_string())
    }
}

/// Converts a lettre `Error` into a `ContactError`.
///
/// Lettre errors during message construction are mapped to `FailedToBuildMessage`.
/// These errors typically occur when building email messages with invalid headers or content.
impl From<lettre::error::Error> for ContactError {
    fn from(value: lettre::error::Error) -> Self {
        Self::FailedToBuildMessage(value.to_string())
    }
}

impl From<ContactError> for Json<ContactResponse> {
    fn from(value: ContactError) -> Self {
        let response: ContactResponse = value.into();
        response.into()
    }
}

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

    #[test]
    fn contact_error_display_could_not_parse_request_email() {
        let error = ContactError::CouldNotParseRequestEmailAddress("invalid".to_string());
        let display = format!("{error}");
        assert!(display.contains("Failed to parse requester's email address"));
        assert!(display.contains("invalid"));
    }

    #[test]
    fn contact_error_display_could_not_parse_settings_email() {
        let error = ContactError::CouldNotParseSettingsEmail("invalid".to_string());
        let display = format!("{error}");
        assert!(display.contains("Failed to parse email address in settings"));
        assert!(display.contains("invalid"));
    }

    #[test]
    fn contact_error_display_failed_to_build_message() {
        let error = ContactError::FailedToBuildMessage("build error".to_string());
        let display = format!("{error}");
        assert!(display.contains("Failed to build the message to be sent"));
        assert!(display.contains("build error"));
    }

    #[test]
    fn contact_error_display_could_not_send_email() {
        let error = ContactError::CouldNotSendEmail("send error".to_string());
        let display = format!("{error}");
        assert!(display.contains("Failed to send the email"));
        assert!(display.contains("send error"));
    }

    #[test]
    fn contact_error_display_validation_error() {
        let error = ContactError::ValidationError("validation error".to_string());
        let display = format!("{error}");
        assert!(display.contains("Failed to validate request"));
        assert!(display.contains("validation error"));
    }

    #[test]
    fn contact_error_display_validation_name_error() {
        let error = ContactError::ValidationNameError("name error".to_string());
        let display = format!("{error}");
        assert!(display.contains("Failed to validate name"));
        assert!(display.contains("name error"));
    }

    #[test]
    fn contact_error_display_validation_email_error() {
        let error = ContactError::ValidationEmailError("email error".to_string());
        let display = format!("{error}");
        assert!(display.contains("Failed to validate email"));
        assert!(display.contains("email error"));
    }

    #[test]
    fn contact_error_display_validation_message_error() {
        let error = ContactError::ValidationMessageError("message error".to_string());
        let display = format!("{error}");
        assert!(display.contains("Failed to validate message"));
        assert!(display.contains("message error"));
    }

    #[test]
    fn contact_error_display_other_error() {
        let error = ContactError::OtherError("other error".to_string());
        let display = format!("{error}");
        assert!(display.contains("Other internal error"));
        assert!(display.contains("other error"));
    }

    #[test]
    fn from_address_error_creates_could_not_parse_settings_email() {
        let address_error: Result<lettre::Address, AddressError> = "invalid email".parse();
        let error: ContactError = address_error.unwrap_err().into();
        match error {
            ContactError::CouldNotParseSettingsEmail(_) => (),
            _ => panic!("Expected CouldNotParseSettingsEmail variant"),
        }
    }

    #[test]
    fn from_lettre_error_creates_failed_to_build_message() {
        // Create an invalid message to trigger a lettre error
        let result = lettre::Message::builder().body(String::new());
        assert!(result.is_err());
        let lettre_error = result.unwrap_err();
        let error: ContactError = lettre_error.into();
        match error {
            ContactError::FailedToBuildMessage(_) => (),
            _ => panic!("Expected FailedToBuildMessage variant"),
        }
    }

    #[test]
    fn from_validation_errors_with_name_error() {
        use validator::Validate;

        #[derive(Validate)]
        struct TestStruct {
            #[validate(length(min = 1))]
            name: String,
        }

        let test = TestStruct {
            name: String::new(),
        };
        let validation_errors = test.validate().unwrap_err();
        let error: ContactError = validation_errors.into();
        match error {
            ContactError::ValidationNameError(msg) => {
                assert_eq!(msg, "backend.contact.errors.validation.name");
            }
            _ => panic!("Expected ValidationNameError variant"),
        }
    }

    #[test]
    fn from_validation_errors_with_email_error() {
        use validator::Validate;

        #[derive(Validate)]
        struct TestStruct {
            #[validate(email)]
            email: String,
        }

        let test = TestStruct {
            email: "invalid".to_string(),
        };
        let validation_errors = test.validate().unwrap_err();
        let error: ContactError = validation_errors.into();
        match error {
            ContactError::ValidationEmailError(msg) => {
                assert_eq!(msg, "backend.contact.errors.validation.email");
            }
            _ => panic!("Expected ValidationEmailError variant"),
        }
    }

    #[test]
    fn from_validation_errors_with_message_error() {
        use validator::Validate;

        #[derive(Validate)]
        struct TestStruct {
            #[validate(length(min = 10))]
            message: String,
        }

        let test = TestStruct {
            message: "short".to_string(),
        };
        let validation_errors = test.validate().unwrap_err();
        let error: ContactError = validation_errors.into();
        match error {
            ContactError::ValidationMessageError(msg) => {
                assert_eq!(msg, "backend.contact.errors.validation.message");
            }
            _ => panic!("Expected ValidationMessageError variant"),
        }
    }

    #[test]
    fn contact_error_to_response_email_validation() {
        let error = ContactError::ValidationEmailError("test".to_string());
        let response: ContactResponse = error.into();
        assert!(!response.success);
        assert_eq!(response.message, "backend.contact.errors.validation.email");
    }

    #[test]
    fn contact_error_to_response_name_validation() {
        let error = ContactError::ValidationNameError("test".to_string());
        let response: ContactResponse = error.into();
        assert!(!response.success);
        assert_eq!(response.message, "backend.contact.errors.validation.name");
    }

    #[test]
    fn contact_error_to_response_message_validation() {
        let error = ContactError::ValidationMessageError("test".to_string());
        let response: ContactResponse = error.into();
        assert!(!response.success);
        assert_eq!(
            response.message,
            "backend.contact.errors.validation.message"
        );
    }

    #[test]
    fn contact_error_to_response_internal_errors() {
        let test_cases = vec![
            ContactError::CouldNotParseSettingsEmail("test".to_string()),
            ContactError::FailedToBuildMessage("test".to_string()),
            ContactError::CouldNotSendEmail("test".to_string()),
            ContactError::OtherError("test".to_string()),
        ];

        for error in test_cases {
            let response: ContactResponse = error.into();
            assert!(!response.success);
            assert_eq!(response.message, "backend.contact.errors.internal");
        }
    }

    #[test]
    fn contact_error_to_response_other_validation() {
        let error = ContactError::ValidationError("test".to_string());
        let response: ContactResponse = error.into();
        assert!(!response.success);
        assert_eq!(response.message, "backend.contact.errors.validation.other");
    }

    #[test]
    fn contact_error_to_json_response() {
        let error = ContactError::ValidationEmailError("test".to_string());
        let json_response: Json<ContactResponse> = error.into();
        assert!(!json_response.0.success);
        assert_eq!(
            json_response.0.message,
            "backend.contact.errors.validation.email"
        );
    }

    #[test]
    fn validation_errors_to_response() {
        use validator::Validate;

        #[derive(Validate)]
        struct TestStruct {
            #[validate(email)]
            email: String,
        }

        let test = TestStruct {
            email: "invalid".to_string(),
        };
        let validation_errors = test.validate().unwrap_err();
        let response: ContactResponse = validation_errors.into();
        assert!(!response.success);
        assert_eq!(response.message, "backend.contact.errors.validation.email");
    }
}