use anyhow::Context;
use rusqlite::{params, OptionalExtension};

/// A version to be incremented whenever the database layout is changed, to refresh it automatically.
const VERSION: usize = 1;

pub fn create(path: impl AsRef<std::path::Path>) -> anyhow::Result<rusqlite::Connection> {
    let path = path.as_ref();
    let mut con = rusqlite::Connection::open(path)?;
    let meta_table = r#"
        CREATE TABLE if not exists meta(
            version int
        )"#;
    con.execute_batch(meta_table)?;
    let version: Option<usize> = con.query_row("SELECT version FROM meta", [], |r| r.get(0)).optional()?;
    match version {
        None => {
            con.execute("INSERT into meta(version) values(?)", params![VERSION])?;
        }
        Some(version) if version != VERSION => match con.close() {
            Ok(()) => {
                std::fs::remove_file(path)
                    .with_context(|| format!("Failed to remove incompatible database file at {path:?}"))?;
                con = rusqlite::Connection::open(path)?;
                con.execute_batch(meta_table)?;
                con.execute("INSERT into meta(version) values(?)", params![VERSION])?;
            }
            Err((_, err)) => return Err(err.into()),
        },
        _ => {}
    }
    con.execute_batch(
        r#"
        CREATE TABLE if not exists commits(
            hash blob(20) NOT NULL PRIMARY KEY
        )
        "#,
    )?;
    // Files are stored as paths which also have an id for referencing purposes
    con.execute_batch(
        r#"
        CREATE TABLE if not exists files(
            file_id integer NOT NULL PRIMARY KEY,
            file_path text UNIQUE
        )
        "#,
    )?;
    con.execute_batch(
        r#"
        CREATE TABLE if not exists commit_file(
            hash blob(20),
            file_id text,
            has_diff boolean NOT NULL,
            lines_added integer NOT NULL,
            lines_removed integer NOT NULL,
            lines_before integer NOT NULL,
            lines_after integer NOT NULL,
            mode integer,
            source_file_id integer,
            FOREIGN KEY (hash) REFERENCES commits (hash),
            FOREIGN KEY (file_id) REFERENCES files (file_id),
            PRIMARY KEY (hash, file_id)
        )
        "#,
    )?;

    Ok(con)
}