vantage-table 0.5.3

Table, Column, and operation traits for the Vantage data framework
Documentation 
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//! HasMany — one-to-many relationship where the foreign key is on the target table.
//!
//! Example: Bakery has many Clients (via client.bakery_id)

use std::fmt::Display;
use std::{any::Any, marker::PhantomData, sync::Arc};

use vantage_core::{Result, error};
use vantage_types::{EmptyEntity, Entity, Record};

use crate::{references::Reference, table::Table, traits::table_source::TableSource};

pub struct HasMany<T: TableSource, SourceE: Entity<T::Value>, TargetE: Entity<T::Value>> {
    /// Foreign key column on the target table (e.g. "bakery_id" on client)
    target_foreign_key: String,
    /// Factory: given a data source, produce the target table
    build_target: Arc<dyn Fn(T) -> Table<T, TargetE> + Send + Sync>,
    _phantom: PhantomData<SourceE>,
}

impl<T: TableSource, SourceE: Entity<T::Value>, TargetE: Entity<T::Value>>
    HasMany<T, SourceE, TargetE>
{
    pub fn new(
        target_foreign_key: impl Into<String>,
        build_target: impl Fn(T) -> Table<T, TargetE> + Send + Sync + 'static,
    ) -> Self {
        Self {
            target_foreign_key: target_foreign_key.into(),
            build_target: Arc::new(build_target),
            _phantom: PhantomData,
        }
    }
}

impl<T: TableSource, SourceE: Entity<T::Value>, TargetE: Entity<T::Value>> Clone
    for HasMany<T, SourceE, TargetE>
{
    fn clone(&self) -> Self {
        Self {
            target_foreign_key: self.target_foreign_key.clone(),
            build_target: self.build_target.clone(),
            _phantom: PhantomData,
        }
    }
}

impl<T: TableSource, SourceE: Entity<T::Value>, TargetE: Entity<T::Value>> std::fmt::Debug
    for HasMany<T, SourceE, TargetE>
{
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("HasMany")
            .field("target_foreign_key", &self.target_foreign_key)
            .finish()
    }
}

impl<
    T: TableSource + 'static,
    SourceE: Entity<T::Value> + 'static,
    TargetE: Entity<T::Value> + 'static,
> Reference for HasMany<T, SourceE, TargetE>
where
    T::Value: Into<ciborium::Value> + From<ciborium::Value>,
    T::Id: Display + From<String>,
{
    fn columns(&self, source_id: &str, _target_id: &str) -> (String, String) {
        (source_id.to_string(), self.target_foreign_key.clone())
    }

    fn build_target(&self, data_source: &dyn Any) -> Box<dyn Any> {
        let ds = data_source
            .downcast_ref::<T>()
            .expect("data source type mismatch in HasMany::build_target");
        Box::new((self.build_target)(ds.clone()))
    }

    fn cardinality(&self) -> vantage_vista::ReferenceKind {
        vantage_vista::ReferenceKind::HasMany
    }

    fn resolve_from_row(
        &self,
        data_source: &dyn Any,
        source_id_field: &str,
        source_row: &dyn Any,
    ) -> Result<Box<dyn Any>> {
        let ds = data_source
            .downcast_ref::<T>()
            .ok_or_else(|| error!("data source type mismatch in HasMany::resolve_from_row"))?;
        let row = source_row
            .downcast_ref::<Record<T::Value>>()
            .ok_or_else(|| error!("source row type mismatch in HasMany::resolve_from_row"))?;

        let mut target = (self.build_target)(ds.clone());
        let (src_col, tgt_col) = self.columns(source_id_field, "");
        let join_value = row
            .get(&src_col)
            .cloned()
            .ok_or_else(|| error!("source row missing id field", field = src_col.as_str()))?;

        let condition = ds.eq_value_condition(&tgt_col, join_value)?;
        target.add_condition(condition);

        Ok(Box::new(target.into_entity::<EmptyEntity>()))
    }

    fn target_type_name(&self) -> &'static str {
        std::any::type_name::<Table<T, TargetE>>()
    }
}