lref 0.1.0

//! Change executor — generates and executes SQL for entity state changes.
//!
//! The `ChangeExecutor` takes a collection of tracked entities grouped by
//! state (Added/Modified/Deleted), generates the appropriate parameterized
//! DML, and executes it against the database via the provider.

use crate::entity::{EntitySnapshot, EntityType, GetKeyValues};
use crate::error::LrefResult;
use crate::metadata::EntityTypeMeta;
use crate::provider::{AsyncConnection, DatabaseProvider, DbValue};
use std::collections::HashMap;

/// Executes INSERT/UPDATE/DELETE for tracked entities within a transaction.
pub struct ChangeExecutor;

impl ChangeExecutor {
    /// Executes INSERT statements for all added entities.
    /// Returns the number of rows inserted.
    /// For auto-increment columns, the generated key values are written back
    /// via the `on_key_backfill` callback.
    pub async fn execute_inserts<E, F>(
        conn: &mut dyn AsyncConnection,
        provider: &dyn DatabaseProvider,
        entities: &[(&E, &EntityTypeMeta)],
        mut on_key_backfill: F,
    ) -> LrefResult<usize>
    where
        E: EntityType + EntitySnapshot + GetKeyValues,
        F: FnMut(usize, i64),
    {
        let gen = provider.sql_generator();
        let mut inserted = 0;

        for (idx, (entity, meta)) in entities.iter().enumerate() {
            let snap = entity.snapshot();
            let scalar_props: Vec<_> = meta.mapped_scalar_properties().collect();
            if scalar_props.is_empty() {
                continue;
            }

            // Build column list (exclude auto-increment primary keys for INSERT)
            let insert_cols: Vec<&str> = scalar_props
                .iter()
                .filter(|p| !p.is_auto_increment || !p.is_primary_key)
                .map(|p| p.column_name.as_ref())
                .collect();

            let params: Vec<DbValue> = scalar_props
                .iter()
                .filter(|p| !p.is_auto_increment || !p.is_primary_key)
                .map(|p| {
                    snap.get(p.field_name.as_ref())
                        .cloned()
                        .unwrap_or(DbValue::Null)
                })
                .collect();

            if insert_cols.is_empty() {
                continue;
            }

            let sql = gen.insert(meta.table_name.as_ref(), &insert_cols, true);
            let rows = conn.execute(&sql, &params).await?;

            // Backfill auto-generated key from RETURNING
            if rows > 0 {
                on_key_backfill(idx, rows as i64);
                inserted += 1;
            }
        }

        Ok(inserted)
    }

    /// Executes UPDATE statements for all modified entities.
    pub async fn execute_updates<E>(
        conn: &mut dyn AsyncConnection,
        provider: &dyn DatabaseProvider,
        entities: &[(&E, &EntityTypeMeta)],
    ) -> LrefResult<usize>
    where
        E: EntityType + EntitySnapshot + GetKeyValues,
    {
        let gen = provider.sql_generator();
        let mut updated = 0;

        for (_entity, meta) in entities {
            let snap = _entity.snapshot();
            let keys = _entity.key_values();
            let scalar_props: Vec<_> = meta.mapped_scalar_properties().collect();

            // SET columns = non-PK + non-auto-increment
            let set_cols: Vec<&str> = scalar_props
                .iter()
                .filter(|p| !p.is_primary_key)
                .map(|p| p.column_name.as_ref())
                .collect();

            if set_cols.is_empty() || keys.is_empty() {
                continue;
            }

            // Build WHERE clause from primary key
            let where_parts: Vec<String> = keys
                .keys()
                .enumerate()
                .map(|(i, k)| {
                    format!(
                        "{} = {}",
                        gen.quote_identifier(k),
                        gen.parameter_placeholder(i + 1)
                    )
                })
                .collect();
            let where_clause = where_parts.join(" AND ");

            let sql = gen.update(meta.table_name.as_ref(), &set_cols, &where_clause);

            // Params: SET values first, then WHERE values
            let mut params: Vec<DbValue> = set_cols
                .iter()
                .map(|col| {
                    // Map column_name back to field_name
                    let prop = scalar_props.iter().find(|p| p.column_name.as_ref() == *col);
                    match prop {
                        Some(p) => snap.get(p.field_name.as_ref()).cloned().unwrap_or(DbValue::Null),
                        None => DbValue::Null,
                    }
                })
                .collect();

            for (_k, v) in &keys {
                params.push(v.clone());
            }

            let rows = conn.execute(&sql, &params).await?;
            if rows > 0 {
                updated += 1;
            }
        }

        Ok(updated)
    }

    /// Executes DELETE statements for all deleted entities.
    pub async fn execute_deletes<E>(
        conn: &mut dyn AsyncConnection,
        provider: &dyn DatabaseProvider,
        entities: &[(&E, &EntityTypeMeta)],
    ) -> LrefResult<usize>
    where
        E: EntityType + GetKeyValues,
    {
        let gen = provider.sql_generator();
        let mut deleted = 0;

        for (_entity, meta) in entities {
            let keys = _entity.key_values();
            if keys.is_empty() {
                continue;
            }

            let where_parts: Vec<String> = keys
                .keys()
                .enumerate()
                .map(|(i, k)| {
                    format!(
                        "{} = {}",
                        gen.quote_identifier(k),
                        gen.parameter_placeholder(i + 1)
                    )
                })
                .collect();
            let where_clause = where_parts.join(" AND ");

            let sql = gen.delete(meta.table_name.as_ref(), &where_clause);

            let params: Vec<DbValue> = keys.values().cloned().collect();
            let rows = conn.execute(&sql, &params).await?;
            if rows > 0 {
                deleted += 1;
            }
        }

        Ok(deleted)
    }
}

// ---------------------------------------------------------------------------
// Standalone SQL generation helpers (for use by simplified callers)
// ---------------------------------------------------------------------------

pub fn generate_insert_sql(
    provider: &dyn DatabaseProvider,
    meta: &EntityTypeMeta,
    _property_values: &HashMap<String, DbValue>,
) -> String {
    let gen = provider.sql_generator();
    let scalar_props: Vec<_> = meta.mapped_scalar_properties().collect();
    let columns: Vec<&str> = scalar_props.iter().map(|p| p.column_name.as_ref()).collect();
    if columns.is_empty() {
        return String::new();
    }
    gen.insert(meta.table_name.as_ref(), &columns, true)
}

pub fn generate_update_sql(
    provider: &dyn DatabaseProvider,
    meta: &EntityTypeMeta,
    property_values: &HashMap<String, DbValue>,
    primary_key_values: &HashMap<String, DbValue>,
) -> String {
    let gen = provider.sql_generator();
    let set_columns: Vec<&str> = property_values
        .keys()
        .filter(|k| !primary_key_values.contains_key(*k))
        .map(|k| k.as_str())
        .collect();
    if set_columns.is_empty() || primary_key_values.is_empty() {
        return String::new();
    }
    let where_parts: Vec<String> = primary_key_values
        .keys()
        .enumerate()
        .map(|(i, k)| format!("{} = {}", gen.quote_identifier(k), gen.parameter_placeholder(i + 1)))
        .collect();
    gen.update(meta.table_name.as_ref(), &set_columns, &where_parts.join(" AND "))
}

pub fn generate_delete_sql(
    provider: &dyn DatabaseProvider,
    meta: &EntityTypeMeta,
    primary_key_values: &HashMap<String, DbValue>,
) -> String {
    let gen = provider.sql_generator();
    if primary_key_values.is_empty() {
        return String::new();
    }
    let where_parts: Vec<String> = primary_key_values
        .keys()
        .enumerate()
        .map(|(i, k)| format!("{} = {}", gen.quote_identifier(k), gen.parameter_placeholder(i + 1)))
        .collect();
    gen.delete(meta.table_name.as_ref(), &where_parts.join(" AND "))
}

pub fn collect_insert_params(
    meta: &EntityTypeMeta,
    property_values: &HashMap<String, DbValue>,
) -> Vec<DbValue> {
    meta.mapped_scalar_properties()
        .map(|p| property_values.get(p.field_name.as_ref()).cloned().unwrap_or(DbValue::Null))
        .collect()
}

pub fn collect_update_params(
    property_values: &HashMap<String, DbValue>,
    primary_key_values: &HashMap<String, DbValue>,
    set_keys: &[String],
) -> Vec<DbValue> {
    let mut params: Vec<DbValue> = set_keys
        .iter()
        .filter(|k| !primary_key_values.contains_key(*k))
        .map(|k| property_values.get(k).cloned().unwrap_or(DbValue::Null))
        .collect();
    for v in primary_key_values.values() {
        params.push(v.clone());
    }
    params
}

pub fn collect_delete_params(primary_key_values: &HashMap<String, DbValue>) -> Vec<DbValue> {
    primary_key_values.values().cloned().collect()
}