rustyroad 1.8.7

Rusty Road is a framework written in Rust that is based on Ruby on Rails. It is designed to provide the familiar conventions and ease of use of Ruby on Rails, while also taking advantage of the performance and efficiency of Rust.
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//! Shared typed equality selectors for read, update and delete operations.

use super::super::{naming::sql, types};
use crate::database::introspection::{Schema, Table};

/// Bound fragments; e.g. a text token produces `"token" = $1` and `.bind(value_1)`.
pub(super) struct Selector {
    pub parameters: String,
    pub predicate: String,
    pub binds: String,
    pub arguments: String,
}

/// Derives read/delete arguments; e.g. `render(table, schema, &["token".into()])`.
pub(super) fn render(table: &Table, schema: &Schema, key: &[String]) -> Selector {
    build(table, schema, key, |position| format!("value_{position}"))
}

/// Names update selectors; e.g. one text column yields `key: String`.
pub(super) fn update(table: &Table, schema: &Schema, key: &[String]) -> Selector {
    build(table, schema, key, |position| key_argument(position, key.len()))
}

/// Names a positional key; e.g. `key_argument(1, 1)` is `key`, not `key_1`.
pub(super) fn key_argument(position: usize, count: usize) -> String {
    if count == 1 {
        "key".to_string()
    } else {
        format!("key_{position}")
    }
}

/// Builds typed bindings; e.g. `build(table, schema, key, |i| format!("key_{i}"))`.
fn build(table: &Table, schema: &Schema, key: &[String], name: impl Fn(usize) -> String) -> Selector {
    let mut parameters = Vec::new();
    let mut predicates = Vec::new();
    let mut arguments = Vec::new();
    let mut binds = String::new();
    for (index, column_name) in key.iter().enumerate() {
        let mut column = table.column(column_name).expect("known selector column").clone();
        column.nullable = false;
        let position = index + 1;
        let argument = name(position);
        parameters.push(format!("{argument}: {}", types::map(&column, schema).rust));
        predicates.push(format!("{} = ${position}", sql(column_name)));
        binds.push_str(&format!(".bind({argument})"));
        arguments.push(argument);
    }
    Selector {
        parameters: parameters.join(", "),
        predicate: predicates.join(" AND "),
        binds,
        arguments: arguments.join(", "),
    }
}