use std::fmt;

use axum::http::{self, StatusCode};
use axum::response::{AppendHeaders, IntoResponse, Response};

use axum::Json;
use serde::{Serialize, Serializer};
use serde_json::{Value, json};

use crate::dns::{DnsDriverError, ZoneDriver};
use crate::dns::record::{RecordError, RecordParseError};
use crate::ressouces::zone::ZoneError;
use crate::validation::{DomainValidationError, TxtParseError};

#[derive(Debug, Serialize)]
pub struct Error {
    #[serde(skip)]
    cause: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none", serialize_with = "serialize_status")]
    status: Option<StatusCode>,
    code: String,
    description: String,
    #[serde(skip_serializing_if = "Option::is_none")]
    details: Option<Value>,
    #[serde(skip_serializing_if = "Option::is_none")]
    path: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    errors: Option<Vec<Error>>,
}

pub fn serialize_status<S>(status: &Option<StatusCode>, serializer: S) -> Result<S::Ok, S::Error>
    where S: Serializer
{
    if let Some(status) = status {
        serializer.serialize_u16(status.as_u16())
    } else {
        serializer.serialize_unit()
    }
}

impl Error {
    pub fn new(code: &str, description: &str) -> Self {
        Error {
            cause: None,
            status: None,
            code: code.into(),
            description: description.into(),
            details: None,
            path: None,
            errors: None
        }
    }

    pub fn with_cause(self, cause: &str) -> Self {
        Self {
            cause: Some(cause.into()),
            ..self
        }
    }

    pub fn with_status(self, status: StatusCode) -> Self {
        Self {
            status: Some(status),
            ..self
        }
    }

    pub fn with_path(self, path: &str) -> Self {
        if let Some(current_path) = self.path {
            Self {
                path: Some(format!("{path}{current_path}")),
                ..self
            }
        } else {
            Self {
                path: Some(path.into()),
                ..self
            }
        }
    }

    pub fn with_details<T: Serialize> (self, details: T) -> Self {
        let mut new_details = serde_json::to_value(details).expect("failed to convert details to serde_json::Value");
        let details = self.details;

        // append new details to existing details
        if let Some(mut details) = details {
            if let Some(object) = details.as_object_mut() {
                if let Some(new_object) = new_details.as_object_mut() {
                    object.append(new_object);

                    return Self {
                        details: Some(details),
                        ..self
                    }
                }
            }
        }

        Self {
            details: Some(new_details),
            ..self
        }

    }

    pub fn with_suberrors(self, mut errors: Vec<Error>) -> Self {
        for error in &mut errors {
            error.status = None;
        }

        Self {
            errors: Some(errors),
            ..self
        }
    }

    pub fn override_status(self, status: StatusCode) -> Self {
        if self.status.is_some() {
            self.with_status(status)
        } else {
            self
        }
    }
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.description)?;

        if let Some(cause) = &self.cause {
            write!(f, ": {}", cause)?;
        }

        if self.status.is_some() || self.details.is_some() {
            write!(f, " (")?;
        }

        if let Some(status) = &self.status {
            write!(f, "status = {}", status)?;
        }

        if let Some(details) = &self.details {
            if self.status.is_some() {
                write!(f, ", ")?;
            }
            write!(f, "details = {}", serde_json::to_string(details).expect("Failed to serialize error details"))?;
        }

        if self.status.is_some() || self.details.is_some() {
            write!(f, ")")?;
        }

        Ok(())
    }
}

impl IntoResponse for Error {
    fn into_response(self) -> Response {
        if let Some(status) = self.status {
            (status, Json(self)).into_response()
        } else {
            eprintln!("{}", self);
            (
                StatusCode::INTERNAL_SERVER_ERROR,
                AppendHeaders([
                    (http::header::CONTENT_TYPE, "application/json")
                ]),
                r#"{"status": 500,"description":"Internal server error","code":"internal"}"#
            ).into_response()
        }
    }
}

impl From<bb8::RunError<rusqlite::Error>> for Error {
    fn from(value: bb8::RunError<rusqlite::Error>) -> Self {
        Error::new("db:pool", "Failed to get database connection from pool")
            .with_cause(&value.to_string())
    }
}

impl From<rusqlite::Error> for Error {
    fn from(value: rusqlite::Error) -> Self {
        Error::new("db:sqlite", "Sqlite failure")
            .with_cause(&format!("{:?}", value))
    }
}

impl From<ZoneError> for Error {
    fn from(value: ZoneError) -> Self {
        match value {
            ZoneError::ZoneConflict { name } => {
                Error::new("zone:conflict", "Zone {zone_name} already exists")
                    .with_details(json!({
                        "zone_name": name
                    }))
                    .with_status(StatusCode::CONFLICT)
            },
            ZoneError::NotFound { name } => {
                Error::new("zone:not_found", "The zone {zone_name} could not be found")
                    .with_details(json!({
                        "zone_name": name
                    }))
                    .with_status(StatusCode::NOT_FOUND)
            },
            ZoneError::Validation { suberrors } => {
                Error::new("zone:validation", "Error while validating zone input data")
                    .with_suberrors(suberrors)
                    .with_status(StatusCode::BAD_REQUEST)
            },
            ZoneError::NotExistsNs { name } => {
                Error::new("zone:not_exists_ns", "The zone {zone_name} does not exist on the name server")
                    .with_details(json!({
                        "zone_name": name
                    }))
                    .with_status(StatusCode::BAD_REQUEST)
            }
        }
    }
}

impl From<DomainValidationError> for Error {
    fn from(value: DomainValidationError) -> Self {
        match value {
            DomainValidationError::CharactersNotPermitted { label } => {
                Error::new("domain:characters_not_permitted", "Domain name label {label} contains characters not permitted. The allowed characters are lowercase alphanumeric characters (a-z and 0-9), the dash ('-'), the underscore ('_') and the forward slash ('/').")
                    .with_details(json!({
                        "label": label
                    }))
            },
            DomainValidationError::EmptyDomain => {
                Error::new("domain:empty_domain", "Domain name can not be empty or the root domain ('.')")
            },
            DomainValidationError::EmptyLabel => {
                Error::new("domain:empty_label", "Domain name contains empty labels (repeated dots)")
            },
            DomainValidationError::DomainTooLong { length } => {
                Error::new("domain:domain_too_long", "Domain name too long ({length} characters), the maximum length is 255 characters")
                    .with_details(json!({
                        "length": length
                    }))
            },
            DomainValidationError::LabelToolLong { length, label } => {
                Error::new("domain:label_too_long", "Domain name label {label} is too long ({label_length} characters), the maximum length is 63 characters")
                    .with_details(json!({
                        "label": label,
                        "length": length,
                    }))
            },
        }
    }
}

impl From<TxtParseError> for Error {
    fn from(value: TxtParseError) -> Self {
        match value {
            TxtParseError::BadEscapeDigitIndexTooHigh { sequence } => {
                Error::new("record:txt:parse:escape_decimal_index_too_high", "Octect escape sequence should be between 000 and 255. Offending escape sequence: \\{sequence}")
                    .with_details(json!({
                        "sequence": sequence
                    }))
            },
            TxtParseError::BadEscapeDigitsNotDigits { sequence } => {
                Error::new("record:txt:parse:escape_decimal_not_digits", "Expected an octect escape sequence due to the presence of a back slash (\\) followed by a digit but found non digit characters. Offending escape sequence: \\{sequence}")
                    .with_details(json!({
                        "sequence": sequence
                    }))
            },
            TxtParseError::BadEscapeDigitsTooShort { sequence } => {
                Error::new("record:txt:parse:escape_decimal_too_short", "Expected an octect escape sequence due to the presence of a back slash (\\) followed by a digit but found found {sequence_lenght} characters instead of three. Offending escape sequence: \\{sequence}")
                    .with_details(json!({
                        "sequence": sequence,
                        "sequence_lenght": sequence.len()
                    }))
            },
            TxtParseError::MissingEscape => {
                Error::new("record:txt:parse:escape_missing", "Expected an escape sequence due to the presence of a back slash (\\) at the end of the input but found nothing")
            },
            TxtParseError::NonAscii { character } => {
                Error::new("record:txt:parse:non_ascii", "Found a non ASCII character ({character}). Only printable ASCII characters are allowed.")
                    .with_details(json!({
                        "character": character
                    }))
            }
        }
    }
}


impl From<DnsDriverError> for Error {
    fn from(value: DnsDriverError) -> Self {

        match value {
            DnsDriverError::ConnectionError { reason } => {
                Error::new("dns:connection", "Error while connecting to the name server")
                    .with_cause(&reason.to_string())
            },
            DnsDriverError::OperationError { reason } => {
                Error::new("dns:operation", "DNS operation error")
                    .with_cause(&reason.to_string())
            },
            DnsDriverError::ServerError { rcode, name, qtype } => {
                Error::new("dns:server", "Unexpected response to query")
                    .with_details(json!({
                        "rcode": rcode,
                        "name": name,
                        "qtype": qtype,
                    }))
            },
            DnsDriverError::ZoneNotFound { name } => {
                Error::new("dns:zone_not_found", "The zone {zone_name} does not exist on the name server")
                    .with_details(json!({
                        "zone_name": name
                    }))
            }
        }
    }
}

impl From<RecordParseError> for Error {
    fn from(value: RecordParseError) -> Self {
        match value {
            RecordParseError::Ip4Address { input } => {
                Error::new("record:parse:ip4", "The following IPv4 address {input} is invalid. IPv4 addresses should have four numbers, each between 0 and 255, separated by dots.")
                    .with_details(json!({
                        "input": input
                    }))
            },
            RecordParseError::Ip6Address { input } => {
                Error::new("record:parse:ip6", "The following IPv4 address {input} is invalid. IPv6 addresses should have eight groups of four hexadecimal digit separated by colons. Leftmost zeros in a group can be omitted, sequence of zeros can be shorted by a double colons.")
                    .with_details(json!({
                        "input": input
                    }))
            },
            RecordParseError::RDataUnknown { input, field, rtype } => {
                Error::new("record:parse:rdata_unknown", "Unknown error while parsing record rdata field")
                    .with_details(json!({
                        "input": input,
                        "field": field,
                        "rtype": rtype,
                    }))
            },
            RecordParseError::NameUnknown { input } => {
                Error::new("record:parse:name_unknown", "Unknown error while parsing record name")
                    .with_details(json!({
                        "input": input
                    }))
            },
            RecordParseError::NotInZone { name, zone } => {
                Error::new("record:parse:not_in_zone", "The domain name {name} is not in the current zone ({zone})")
                    .with_details(json!({
                        "name": name,
                        "zone": zone
                    }))
            }
        }
    }
}

impl From<RecordError > for Error {
    fn from(value: RecordError) -> Self {
        match value {
            RecordError::Validation { suberrors } => {
                Error::new("record:validation", "Error while validating input records")
                    .with_suberrors(suberrors)
                    .with_status(StatusCode::BAD_REQUEST)
            }
        }
    }
}