use chrono::{DateTime, Utc};
use interim_pgtypes::pg_attribute::PgAttribute;
use serde::{Deserialize, Serialize};
use sqlx::{Decode, Postgres, Row as _, TypeInfo as _, ValueRef as _, postgres::PgRow};
use thiserror::Error;
use uuid::Uuid;

const RFC_3339_S: &str = "%Y-%m-%dT%H:%M:%S";

/// A single column which can be passed to a front-end viewer. A Selection may
/// resolve to zero or more Fields.
#[derive(Clone, Debug, Deserialize, Serialize)]
pub struct Field {
    pub name: String,
    pub label: Option<String>,
    pub field_type: sqlx::types::Json<FieldType>,
    pub width_px: i32,
}

impl Field {
    pub fn default_from_attr(attr: &PgAttribute) -> Self {
        Self {
            name: attr.attname.clone(),
            label: None,
            field_type: sqlx::types::Json(FieldType::default_from_attr(attr)),
            width_px: 200,
        }
    }

    pub fn webc_tag(&self) -> &str {
        match self.field_type.0 {
            FieldType::Integer => "cell-integer",
            FieldType::InterimUser => "cell-interim-user",
            FieldType::Text => "cell-text",
            FieldType::Timestamp { .. } => "cell-timestamp",
            FieldType::Uuid => "cell-uuid",
            FieldType::Unknown => "cell-unknown",
        }
    }

    pub fn webc_custom_attrs(&self) -> Vec<(String, String)> {
        vec![]
    }

    pub fn render(&self, value: &Encodable) -> String {
        match (self.field_type.0.clone(), value) {
            (FieldType::Integer, Encodable::Integer(Some(value))) => value.to_string(),
            (FieldType::Integer, Encodable::Integer(None)) => "".to_owned(),
            (FieldType::Integer, _) => "###".to_owned(),
            (FieldType::InterimUser, Encodable::Text(value)) => todo!(),
            (FieldType::InterimUser, _) => "###".to_owned(),
            (FieldType::Text, Encodable::Text(Some(value))) => value.clone(),
            (FieldType::Text, Encodable::Text(None)) => "".to_owned(),
            (FieldType::Text, _) => "###".to_owned(),
            (FieldType::Timestamp { format }, Encodable::Timestamptz(value)) => value
                .map(|value| value.format(&format).to_string())
                .unwrap_or("".to_owned()),
            (FieldType::Timestamp { .. }, _) => "###".to_owned(),
            (FieldType::Uuid, Encodable::Uuid(Some(value))) => value.hyphenated().to_string(),
            (FieldType::Uuid, Encodable::Uuid(None)) => "".to_owned(),
            (FieldType::Uuid, _) => "###".to_owned(),
            (FieldType::Unknown, _) => "###".to_owned(),
        }
    }

    pub fn get_value_encodable(&self, row: &PgRow) -> Result<Encodable, ParseError> {
        let value_ref = row
            .try_get_raw(self.name.as_str())
            .or(Err(ParseError::FieldNotFound))?;
        let type_info = value_ref.type_info();
        let ty = type_info.name();
        Ok(match ty {
            "INT" | "INT4" => {
                Encodable::Integer(<Option<i32> as Decode<Postgres>>::decode(value_ref).unwrap())
            }
            "TEXT" | "VARCHAR" => {
                Encodable::Text(<Option<String> as Decode<Postgres>>::decode(value_ref).unwrap())
            }
            "UUID" => {
                Encodable::Uuid(<Option<Uuid> as Decode<Postgres>>::decode(value_ref).unwrap())
            }
            _ => return Err(ParseError::UnknownType),
        })
    }
}

#[derive(Clone, Debug, Deserialize, Serialize)]
#[serde(tag = "t", content = "c")]
pub enum FieldType {
    Integer,
    InterimUser,
    Text,
    Timestamp {
        format: String,
    },
    Uuid,
    /// A special variant for when the field type is not specified and cannot be
    /// inferred. This isn't represented as an error, because we still want to
    /// be able to define display behavior via the .render() method.
    Unknown,
}

impl FieldType {
    pub fn default_from_attr(attr: &PgAttribute) -> Self {
        match attr.regtype.as_str() {
            "integer" => Self::Integer,
            "text" => Self::Text,
            "timestamp" => Self::Timestamp {
                format: RFC_3339_S.to_owned(),
            },
            "uuid" => Self::Uuid,
            _ => Self::Unknown,
        }
    }
}

/// Error when parsing a sqlx value to JSON
#[derive(Debug, Error)]
pub enum ParseError {
    #[error("incompatible json type")]
    BadJsonType,
    #[error("field not found in row")]
    FieldNotFound,
    #[error("unknown postgres type")]
    UnknownType,
}

#[derive(Clone, Debug, Deserialize, PartialEq, Serialize)]
#[serde(tag = "t", content = "c")]
pub enum Encodable {
    Integer(Option<i32>),
    Text(Option<String>),
    Timestamptz(Option<DateTime<Utc>>),
    Uuid(Option<Uuid>),
}

impl Encodable {
    pub fn bind_onto<'a>(
        &'a self,
        query: sqlx::query::Query<'a, Postgres, <sqlx::Postgres as sqlx::Database>::Arguments<'a>>,
    ) -> sqlx::query::Query<'a, Postgres, <sqlx::Postgres as sqlx::Database>::Arguments<'a>> {
        match self {
            Self::Integer(value) => query.bind(value),
            Self::Text(value) => query.bind(value),
            Self::Timestamptz(value) => query.bind(value),
            Self::Uuid(value) => query.bind(value),
        }
    }
}

// impl<'a> Encode<'a, Postgres> for Encodable {
//     fn encode_by_ref(
//         &self,
//         buf: &mut <Postgres as sqlx::Database>::ArgumentBuffer<'a>,
//     ) -> Result<sqlx::encode::IsNull, sqlx::error::BoxDynError> {
//         match self {
//             Self::Integer(value) => Encode::<'a, Postgres>::encode(value, buf),
//             Self::Text(value) => Encode::<'a, Postgres>::encode(value, buf),
//             Self::Timestamptz(value) => Encode::<'a, Postgres>::encode(value, buf),
//             Self::Uuid(value) => Encode::<'a, Postgres>::encode(value, buf),
//         }
//     }
// }
//
// impl<'a> Decode<'a, Postgres> for FieldType {
//     fn decode(
//         value: <Postgres as sqlx::Database>::ValueRef<'a>,
//     ) -> Result<Self, sqlx::error::BoxDynError> {
//         let value: String = Decode::<'a, Postgres>::decode(value)?;
//         Ok(serde_json::from_str(&value)?)
//     }
// }