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use crate::sql_entity_graph::{pgx_sql::PgxSql, to_sql::ToSqlFn, SqlGraphEntity};

/// Represents configuration options for tuning the SQL generator.
///
/// When an item that can be rendered to SQL has these options at hand, they should be
/// respected. If an item does not have them, then it is not expected that the SQL generation
/// for those items can be modified.
///
/// The default configuration has `enabled` set to `true`, and `callback` to `None`, which indicates
/// that the default SQL generation behavior will be used. These are intended to be mutually exclusive
/// options, so `callback` should only be set if generation is enabled.
///
/// When `enabled` is false, no SQL is generated for the item being configured.
///
/// When `callback` has a value, the corresponding `ToSql` implementation should invoke the
/// callback instead of performing their default behavior.
#[derive(Default, Clone)]
pub struct ToSqlConfigEntity {
    pub enabled: bool,
    pub callback: Option<ToSqlFn>,
    pub content: Option<&'static str>,
}
impl ToSqlConfigEntity {
    /// Given a SqlGraphEntity, this function converts it to SQL based on the current configuration.
    ///
    /// If the config overrides the default behavior (i.e. using the `ToSql` trait), then `Some(eyre::Result)`
    /// is returned. If the config does not override the default behavior, then `None` is returned. This can
    /// be used to dispatch SQL generation in a single line, e.g.:
    ///
    /// ```rust,ignore
    /// config.to_sql(entity, context).unwrap_or_else(|| entity.to_sql(context))?
    /// ```
    pub fn to_sql(
        &self,
        entity: &SqlGraphEntity,
        context: &PgxSql,
    ) -> Option<eyre::Result<String>> {
        use eyre::{eyre, WrapErr};

        if !self.enabled {
            return Some(Ok(format!(
                "\n\
                {sql_anchor_comment}\n\
                -- Skipped due to `#[pgx(sql = false)]`\n",
                sql_anchor_comment = entity.sql_anchor_comment(),
            )));
        }

        if let Some(content) = self.content {
            return Some(Ok(format!(
                "\n\
                {sql_anchor_comment}\n\
                {content}\n\
            ",
                content = content,
                sql_anchor_comment = entity.sql_anchor_comment()
            )));
        }

        if let Some(callback) = self.callback {
            let content = callback(entity, context)
                .map_err(|e| eyre!(e))
                .wrap_err("Failed to run specified `#[pgx(sql = path)] function`");
            return match content {
                Ok(content) => Some(Ok(format!(
                    "\n\
                        {sql_anchor_comment}\n\
                        {content}\
                    ",
                    content = content,
                    sql_anchor_comment = entity.sql_anchor_comment(),
                ))),
                Err(e) => Some(Err(e)),
            };
        }

        None
    }
}
impl std::cmp::PartialEq for ToSqlConfigEntity {
    fn eq(&self, other: &Self) -> bool {
        if self.enabled != other.enabled {
            return false;
        }
        match (self.callback, other.callback) {
            (None, None) => match (self.content, other.content) {
                (None, None) => true,
                (Some(a), Some(b)) => a == b,
                _ => false,
            },
            (Some(a), Some(b)) => std::ptr::eq(std::ptr::addr_of!(a), std::ptr::addr_of!(b)),
            _ => false,
        }
    }
}
impl std::cmp::Eq for ToSqlConfigEntity {}
impl std::hash::Hash for ToSqlConfigEntity {
    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
        self.enabled.hash(state);
        self.callback.map(|cb| std::ptr::addr_of!(cb)).hash(state);
        self.content.hash(state);
    }
}
impl std::fmt::Debug for ToSqlConfigEntity {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        let callback = self.callback.map(|cb| std::ptr::addr_of!(cb));
        f.debug_struct("ToSqlConfigEntity")
            .field("enabled", &self.enabled)
            .field("callback", &format_args!("{:?}", &callback))
            .field("content", &self.content)
            .finish()
    }
}