//! Registry of flexible field definitions.

use domain::{
    AuthorityKind, FieldDefinition, FieldDefinitionId, FieldType, LocalizedLabel,
    NewFieldDefinition, VocabularyId,
};
use sqlx::Row;

/// Labels aggregated per row as JSON, to read a definition and its labels in one query.
const LABELS_JSON: &str = "COALESCE(json_agg(json_build_object('lang', fdl.lang, 'label', fdl.label) \
     ORDER BY fdl.lang) FILTER (WHERE fdl.field_definition_id IS NOT NULL), '[]'::json)";

const SELECT_COLUMNS: &str =
    "fd.id, fd.key, fd.data_type, fd.vocabulary_id, fd.authority_kind, fd.required, fd.group_key";

/// Create a field definition and its labels. Multiple statements — pass a
/// transaction connection (`&mut *tx`) for atomicity.
pub async fn create_field_definition(
    conn: &mut sqlx::PgConnection,
    new: &NewFieldDefinition,
) -> Result<FieldDefinitionId, sqlx::Error> {
    let id = FieldDefinitionId::new();
    let (data_type, vocabulary_id, authority_kind) = new.field_type.to_parts();

    sqlx::query(
        "INSERT INTO field_definition \
         (id, key, data_type, vocabulary_id, authority_kind, required, group_key) \
         VALUES ($1, $2, $3, $4, $5, $6, $7)",
    )
    .bind(id.to_uuid())
    .bind(&new.key)
    .bind(data_type)
    .bind(vocabulary_id.map(|v| v.to_uuid()))
    .bind(authority_kind.map(|k| k.as_str()))
    .bind(new.required)
    .bind(new.group_key.as_deref())
    .execute(&mut *conn)
    .await?;

    for label in &new.labels {
        sqlx::query(
            "INSERT INTO field_definition_label (field_definition_id, lang, label) \
             VALUES ($1, $2, $3)",
        )
        .bind(id.to_uuid())
        .bind(&label.lang)
        .bind(&label.label)
        .execute(&mut *conn)
        .await?;
    }

    Ok(id)
}

/// Look up a field definition by its key (with labels).
pub async fn field_definition_by_key<'e, E>(
    executor: E,
    key: &str,
) -> Result<Option<FieldDefinition>, sqlx::Error>
where
    E: sqlx::PgExecutor<'e>,
{
    let sql = format!(
        "SELECT {SELECT_COLUMNS}, {LABELS_JSON} AS labels \
         FROM field_definition fd \
         LEFT JOIN field_definition_label fdl ON fdl.field_definition_id = fd.id \
         WHERE fd.key = $1 GROUP BY fd.id"
    );

    let row = sqlx::query(&sql).bind(key).fetch_optional(executor).await?;

    row.map(map_field_definition).transpose()
}

/// List all field definitions (with labels), ordered by key.
pub async fn list_field_definitions<'e, E>(executor: E) -> Result<Vec<FieldDefinition>, sqlx::Error>
where
    E: sqlx::PgExecutor<'e>,
{
    let sql = format!(
        "SELECT {SELECT_COLUMNS}, {LABELS_JSON} AS labels \
         FROM field_definition fd \
         LEFT JOIN field_definition_label fdl ON fdl.field_definition_id = fd.id \
         GROUP BY fd.id ORDER BY fd.key"
    );

    let rows = sqlx::query(&sql).fetch_all(executor).await?;

    rows.into_iter().map(map_field_definition).collect()
}

fn map_field_definition(row: sqlx::postgres::PgRow) -> Result<FieldDefinition, sqlx::Error> {
    let data_type: String = row.try_get("data_type")?;
    let vocabulary_id: Option<uuid::Uuid> = row.try_get("vocabulary_id")?;
    let authority_kind: Option<String> = row.try_get("authority_kind")?;

    let authority_kind = authority_kind
        .map(|k| {
            AuthorityKind::from_db(&k)
                .ok_or_else(|| sqlx::Error::Decode(format!("unknown authority kind: {k}").into()))
        })
        .transpose()?;

    let field_type = FieldType::from_parts(
        &data_type,
        vocabulary_id.map(VocabularyId::from_uuid),
        authority_kind,
    )
    .ok_or_else(|| {
        sqlx::Error::Decode(format!("inconsistent field type stored: {data_type}").into())
    })?;

    let labels: sqlx::types::Json<Vec<LocalizedLabel>> = row.try_get("labels")?;

    Ok(FieldDefinition {
        id: FieldDefinitionId::from_uuid(row.try_get("id")?),
        key: row.try_get("key")?,
        field_type,
        required: row.try_get("required")?,
        group_key: row.try_get("group_key")?,
        labels: labels.0,
    })
}