use std::collections::HashMap;

use axum::{
    Json,
    extract::{Path, State},
    response::{IntoResponse as _, Response},
};
use interim_models::{datum::Datum, field::Field, portal::Portal};
use interim_pgtypes::{escape_identifier, pg_attribute::PgAttribute, pg_class::PgClass};
use serde::{Deserialize, Serialize};
use sqlx::{postgres::PgRow, query};
use uuid::Uuid;

use crate::{
    app::AppDbConn,
    errors::AppError,
    field_info::FieldInfo,
    user::CurrentUser,
    workspace_pooler::{RoleAssignment, WorkspacePooler},
};

#[derive(Clone, Debug, Deserialize)]
pub(super) struct PathParams {
    portal_id: Uuid,
}

const FRONTEND_ROW_LIMIT: i64 = 1000;

/// HTTP GET handler for an API endpoint returning a JSON encoding of portal
/// data to display in a table or similar form.
///
/// Only queries up to the first [`FRONTEND_ROW_LIMIT`] rows.
pub(super) async fn get(
    State(mut workspace_pooler): State<WorkspacePooler>,
    AppDbConn(mut app_db): AppDbConn,
    CurrentUser(current_user): CurrentUser,
    Path(PathParams { portal_id }): Path<PathParams>,
) -> Result<Response, AppError> {
    // FIXME auth
    let portal = Portal::with_id(portal_id).fetch_one(&mut app_db).await?;

    let mut workspace_client = workspace_pooler
        .acquire_for(portal.workspace_id, RoleAssignment::User(current_user.id))
        .await?;
    let rel = PgClass::with_oid(portal.class_oid)
        .fetch_one(&mut workspace_client)
        .await?;

    let attrs = PgAttribute::all_for_rel(portal.class_oid)
        .fetch_all(&mut workspace_client)
        .await?;
    let pkey_attrs = PgAttribute::pkeys_for_rel(portal.class_oid)
        .fetch_all(&mut workspace_client)
        .await?;

    let fields: Vec<FieldInfo> = {
        let fields: Vec<Field> = Field::belonging_to_portal(portal.id)
            .fetch_all(&mut app_db)
            .await?;
        let mut field_info: Vec<FieldInfo> = Vec::with_capacity(fields.len());
        for field in fields {
            if let Some(attr) = attrs.iter().find(|attr| attr.attname == field.name) {
                field_info.push(FieldInfo {
                    field,
                    has_default: attr.atthasdef,
                    not_null: attr.attnotnull.unwrap_or_default(),
                });
            }
        }
        field_info
    };

    let mut sql_raw = format!(
        "select {0} from {1}.{2}",
        pkey_attrs
            .iter()
            .chain(attrs.iter())
            .map(|attr| escape_identifier(&attr.attname))
            .collect::<Vec<_>>()
            .join(", "),
        escape_identifier(&rel.regnamespace),
        escape_identifier(&rel.relname),
    );
    let rows: Vec<PgRow> = if let Some(filter_expr) = portal.table_filter.0 {
        let filter_fragment = filter_expr.into_query_fragment();
        let filter_params = filter_fragment.to_params();
        sql_raw = format!(
            "{sql_raw} where {0} limit ${1}",
            filter_fragment.to_sql(1),
            filter_params.len() + 1
        );
        let mut q = query(&sql_raw);
        for param in filter_params {
            q = param.bind_onto(q);
        }
        q = q.bind(FRONTEND_ROW_LIMIT);
        q.fetch_all(workspace_client.get_conn()).await?
    } else {
        sql_raw = format!("{sql_raw} limit $1");
        query(&sql_raw)
            .bind(FRONTEND_ROW_LIMIT)
            .fetch_all(workspace_client.get_conn())
            .await?
    };

    #[derive(Serialize)]
    struct DataRow {
        pkey: String,
        data: Vec<Datum>,
    }

    let mut data_rows: Vec<DataRow> = vec![];
    let mut pkeys: Vec<String> = vec![];
    for row in rows.iter() {
        let mut pkey_values: HashMap<String, Datum> = HashMap::new();
        for attr in pkey_attrs.clone() {
            let field = Field::default_from_attr(&attr)
                .ok_or(anyhow::anyhow!("unsupported primary key column type"))?;
            pkey_values.insert(field.name.clone(), field.get_datum(row)?);
        }
        let pkey = serde_json::to_string(&pkey_values)?;
        pkeys.push(pkey.clone());
        let mut row_data: Vec<Datum> = vec![];
        for field in fields.iter() {
            row_data.push(field.field.get_datum(row)?);
        }
        data_rows.push(DataRow {
            pkey,
            data: row_data,
        });
    }

    #[derive(Serialize)]
    struct ResponseBody {
        rows: Vec<DataRow>,
        fields: Vec<FieldInfo>,
        pkeys: Vec<String>,
    }
    Ok(Json(ResponseBody {
        rows: data_rows,
        fields,
        pkeys,
    })
    .into_response())
}