module db;

import std.algorithm;
import std.array;
import std.typecons;
import std.conv;
import std.string : split, strip;

import ddbc;
import slf4d;
import handy_httpd.components.optional;
import handy_httpd;

private DataSource dataSource;

static this() {
    import std.process : environment;
    string username = environment.get("TEACHER_TOOLS_DB_USERNAME", "teacher-tools-dev");
    string password = environment.get("TEACHER_TOOLS_DB_PASSWORD", "testpass");
    string dbUrl = environment.get("TEACHER_TOOLS_DB_URL", "postgresql://localhost:5432/teacher-tools-dev");
    string connectionStr = dbUrl ~ "?user=" ~ username ~ ",password=" ~ password;

    dataSource = createDataSource(connectionStr);
}

Connection getDb() {
    return dataSource.getConnection();
}

void initializeSchema() {
    info("Initializing database schema.");
    Connection conn = getDb();
    scope(exit) conn.close();
    Statement stmt = conn.createStatement();
    scope(exit) stmt.close();
    const string AUTH_SCHEMA = import("schema/auth.sql");
    const string CLASSROOM_COMPLIANCE_SCHEMA = import("schema/classroom_compliance.sql");
    const schemas = [AUTH_SCHEMA, CLASSROOM_COMPLIANCE_SCHEMA];
    uint schemaNumber = 1;
    foreach (schema; schemas) {
        infoF!"Intializing schema #%d."(schemaNumber++);
        auto statements = schema.split(";")
            .map!(s => strip(s))
            .filter!(s => s.length > 0);
        uint stmtNumber = 1;
        foreach (statementStr; statements) {
            infoF!"Executing statement #%d."(stmtNumber++);
            try {
                stmt.executeUpdate(statementStr);
            } catch (SQLException e) {
                error(e, "Failed to execute schema statement.");
                throw new HttpStatusException(
                    HttpStatus.INTERNAL_SERVER_ERROR,
                    "Failed to initialize schema. See logs for more info."
                );
            }
        }
    }
}

T[] findAll(T, Args...)(
    Connection conn,
    string query,
    T function(DataSetReader) parser,
    Args args
) {
    PreparedStatement ps = conn.prepareStatement(query);
    scope(exit) ps.close();
    bindAllArgs(ps, args);
    ResultSet rs = ps.executeQuery();
    scope(exit) rs.close();
    Appender!(T[]) app;
    foreach (row; rs) {
        app ~= parser(row);
    }
    return app[];
}

Optional!T findOne(T, Args...)(
    Connection conn,
    string query,
    T function(DataSetReader) parser,
    Args args
) {
    PreparedStatement ps = conn.prepareStatement(query);
    scope(exit) ps.close();
    bindAllArgs(ps, args);
    ResultSet rs = ps.executeQuery();
    scope(exit) rs.close();
    if (rs.next()) {
        return Optional!T.of(parser(rs));
    }
    return Optional!T.empty;
}

ulong count(Args...)(Connection conn, string query, Args args) {
    return findOne(conn, query, r => r.getUlong(1), args).orElse(0);
}

bool recordExists(Args...)(Connection conn, string query, Args args) {
    PreparedStatement ps = conn.prepareStatement(query);
    scope(exit) ps.close();
    bindAllArgs(ps, args);
    ResultSet rs = ps.executeQuery();
    scope(exit) rs.close();
    return rs.next();
}

ulong insertOne(Args...)(Connection conn, string query, Args args) {
    PreparedStatement ps = conn.prepareStatement(query);
    scope(exit) ps.close();
    bindAllArgs(ps, args);
    import std.variant;
    Variant insertedId;
    int affectedRows = ps.executeUpdate(insertedId);
    if (affectedRows != 1) {
        throw new Exception("Failed to insert exactly 1 row.");
    }
    return insertedId.coerce!ulong;
}

int update(Args...)(Connection conn, string query, Args args) {
    PreparedStatement ps = conn.prepareStatement(query);
    scope(exit) ps.close();
    bindAllArgs(ps, args);
    return ps.executeUpdate();
}

void bindAllArgs(Args...)(PreparedStatement ps, Args args) {
    int idx;
    static foreach (i, arg; args) {
        idx = i + 1;
        static if (is(typeof(arg) == string)) ps.setString(idx, arg);
        else static if (is(typeof(arg) == const(string))) ps.setString(idx, arg);
        else static if (is(typeof(arg) == bool)) ps.setBoolean(idx, arg);
        else static if (is(typeof(arg) == ulong)) ps.setUlong(idx, arg);
        else static if (is(typeof(arg) == const(ulong))) ps.setUlong(idx, arg);
        else static if (is(typeof(arg) == ushort)) ps.setUshort(idx, arg);
        else static if (is(typeof(arg) == const(ushort))) ps.setUshort(idx, arg);
        else static if (is(typeof(arg) == int)) ps.setInt(idx, arg);
        else static if (is(typeof(arg) == const(int))) ps.setInt(idx, arg);
        else static if (is(typeof(arg) == uint)) ps.setUint(idx, arg);
        else static if (is(typeof(arg) == const(uint))) ps.setUint(idx, arg);
        else static assert(false, "Unsupported argument type: " ~ (typeof(arg).stringof));
    }
}