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// Copyright (c) 2022  Teddy Wing
//
// This file is part of Yaqlite.
//
// Yaqlite is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Yaqlite is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Yaqlite. If not, see <https://www.gnu.org/licenses/>.

use rusqlite;
use yaml_rust::yaml;

use std::collections::HashSet;


mod sql;
mod write;

pub(crate) use sql::*;

pub use write::*;


/// Insert a YAML document into the given table in the database.
pub fn db_insert(
    doc: &mut yaml::Yaml,
    tx: &rusqlite::Transaction,
    table_name: &str,
    table_columns: &HashSet<String>,
) -> Result<(), crate::Error> {
    with_hash(
        doc,
        &mut |hash| {
            use std::borrow::Cow;

            hash_filter_table_columns(hash, &table_columns);

            let mut stmt = tx.prepare(
                &format!(
                    r#"
                        INSERT INTO "{}"
                            ({})
                        VALUES
                            ({});
                    "#,
                    table_name,

                    // Wrap column names in quotes.
                    hash.keys()
                        .map(|k| k.as_str())
                        .filter(|k| k.is_some())

                        // Always `Some`.
                        .map(|k| format!(r#""{}""#, k.unwrap()))
                        .collect::<Vec<String>>()
                        .join(", "),
                    format!("{}?", "?, ".repeat(hash.len() - 1)),
                )
            )?;

            let values = hash.values().map(|v| Yaml(Cow::Borrowed(v)));
            stmt.insert(rusqlite::params_from_iter(values))?;

            Ok(())
        }
    )
}

/// Parse a YAML document and run a function for all hashes in the document.
fn with_hash<F>(
    doc: &mut yaml::Yaml,
    run: &mut F,
) -> Result<(), crate::Error>
where F: FnMut(&mut yaml::Hash) -> Result<(), crate::Error>
{
    match doc {
        yaml::Yaml::Array(ref mut array) => {
            for yaml_value in array {
                with_hash(yaml_value, run)?;
            }
        }
        yaml::Yaml::Hash(ref mut hash) => {
            run(hash)?;
        }
        _ => {}
    }

    Ok(())
}

/// Remove keys in `table_columns` from `hash`.
fn hash_filter_table_columns(
    hash: &mut yaml::Hash,
    table_columns: &HashSet<String>,
) {
    let keys: Vec<yaml::Yaml> = hash.keys().map(|k| k.clone()).collect();
    let columns_as_yaml: Vec<yaml::Yaml> = table_columns.iter()
        .map(|c| yaml::Yaml::from_str(c))
        .collect();

    for key in keys.iter() {
        if !columns_as_yaml.contains(key) {
            hash.remove(key);
        }
    }
}