//! `local_records` and `forward_zones`.
//!
//! The import path is list / insert / deleteAll / count. The REST surface
//! follows each table's section: it speaks row ids, because that is what an
//! `/api/local-records/{id}` or `/api/forward-zones/{id}` request names.

const std = @import("std");
const Allocator = std.mem.Allocator;

const db = @import("../db.zig");
const migrations = @import("../migrations.zig");
const model = @import("../../config/model.zig");
const context = @import("context.zig");
const crud = @import("crud.zig");

const InsertContext = context.InsertContext;

// ---------------------------------------------------------------------------
// local_records
// ---------------------------------------------------------------------------

const list_local_records_sql =
    \\SELECT name, rtype, value, ttl FROM local_records ORDER BY name, rtype, value
;

/// Every string in the result is a heap copy owned by `gpa`.
pub fn listLocalRecords(database: *db.Db, gpa: Allocator) db.Error!std.ArrayList(model.LocalRecord) {
    return crud.listRows(model.LocalRecord, database, gpa, list_local_records_sql, readLocalRecord);
}

fn readLocalRecord(stmt: *db.Stmt, gpa: Allocator) db.Error!model.LocalRecord {
    // The DDL's CHECK constraint makes the decode total for any row nxdns
    // wrote; `error.Mismatch` covers a row that something else wrote.
    const rtype = model.RecordType.fromDb(stmt.columnText(1)) orelse return error.Mismatch;
    const ttl = std.math.cast(u32, stmt.columnInt(3)) orelse return error.Mismatch;
    const name = try stmt.columnTextAlloc(gpa, 0);
    errdefer gpa.free(name);
    const value = try stmt.columnTextAlloc(gpa, 2);
    errdefer gpa.free(value);
    return .{ .name = name, .rtype = rtype, .value = value, .ttl = ttl };
}

pub fn freeLocalRecords(gpa: Allocator, items: []const model.LocalRecord) void {
    crud.freeRows(model.LocalRecord, gpa, items);
}

const insert_local_record_sql =
    \\INSERT INTO local_records (name, rtype, value, ttl) VALUES (?1, ?2, ?3, ?4)
;

pub fn insertLocalRecord(database: *db.Db, item: model.LocalRecord, ctx: InsertContext) db.Error!void {
    _ = ctx;
    var stmt = try database.prepare(insert_local_record_sql);
    defer stmt.deinit();
    try stmt.bindText(1, item.name);
    try stmt.bindText(2, item.rtype.toDb());
    try stmt.bindText(3, item.value);
    try stmt.bindInt(4, item.ttl);
    try stmt.exec();
}

pub fn deleteAllLocalRecords(database: *db.Db) db.Error!void {
    return database.exec("DELETE FROM local_records;");
}

pub fn countLocalRecords(database: *db.Db) db.Error!i64 {
    return database.queryInt("SELECT count(*) FROM local_records");
}

// ---------------------------------------------------------------------------
// forward_zones
// ---------------------------------------------------------------------------

pub fn listForwardZones(database: *db.Db, gpa: Allocator) db.Error!std.ArrayList(model.ForwardZone) {
    return crud.listRows(
        model.ForwardZone,
        database,
        gpa,
        "SELECT zone, resolver FROM forward_zones ORDER BY zone",
        readForwardZone,
    );
}

fn readForwardZone(stmt: *db.Stmt, gpa: Allocator) db.Error!model.ForwardZone {
    const zone = try stmt.columnTextAlloc(gpa, 0);
    errdefer gpa.free(zone);
    const resolver = try stmt.columnTextAlloc(gpa, 1);
    errdefer gpa.free(resolver);
    return .{ .zone = zone, .resolver = resolver };
}

pub fn freeForwardZones(gpa: Allocator, items: []const model.ForwardZone) void {
    crud.freeRows(model.ForwardZone, gpa, items);
}

pub fn insertForwardZone(database: *db.Db, item: model.ForwardZone, ctx: InsertContext) db.Error!void {
    _ = ctx;
    var stmt = try database.prepare("INSERT INTO forward_zones (zone, resolver) VALUES (?1, ?2)");
    defer stmt.deinit();
    try stmt.bindText(1, item.zone);
    try stmt.bindText(2, item.resolver);
    try stmt.exec();
}

pub fn deleteAllForwardZones(database: *db.Db) db.Error!void {
    return database.exec("DELETE FROM forward_zones;");
}

pub fn countForwardZones(database: *db.Db) db.Error!i64 {
    return database.queryInt("SELECT count(*) FROM forward_zones");
}

// ---------------------------------------------------------------------------
// REST surface (milestone 8)
// ---------------------------------------------------------------------------
//
// Neither table references another, so the write shapes are `model.LocalRecord`
// and `model.ForwardZone` unchanged: their fields are exactly the columns.

pub const LocalRecordRow = struct {
    id: i64,
    name: []const u8,
    rtype: model.RecordType,
    value: []const u8,
    ttl: u32,
};

const list_local_record_rows_sql =
    \\SELECT id, name, rtype, value, ttl FROM local_records ORDER BY name, rtype, value
;

/// Same order as `listLocalRecords`; every string is a heap copy owned by `gpa`.
pub fn listLocalRecordRows(database: *db.Db, gpa: Allocator) db.Error!std.ArrayList(LocalRecordRow) {
    return crud.listRows(LocalRecordRow, database, gpa, list_local_record_rows_sql, readLocalRecordRow);
}

pub fn freeLocalRecordRow(gpa: Allocator, row: LocalRecordRow) void {
    crud.freeRow(LocalRecordRow, gpa, row);
}

pub fn freeLocalRecordRows(gpa: Allocator, items: []const LocalRecordRow) void {
    crud.freeRows(LocalRecordRow, gpa, items);
}

pub fn getLocalRecord(database: *db.Db, gpa: Allocator, id: i64) db.Error!?LocalRecordRow {
    var stmt = try database.prepare("SELECT id, name, rtype, value, ttl FROM local_records WHERE id = ?1");
    defer stmt.deinit();
    try stmt.bindInt(1, id);
    if (!try stmt.step()) return null;
    return try readLocalRecordRow(&stmt, gpa);
}

fn readLocalRecordRow(stmt: *db.Stmt, gpa: Allocator) db.Error!LocalRecordRow {
    // The DDL's CHECK constraint makes the decode total for any row nxdns
    // wrote; `error.Mismatch` covers a row that something else wrote, and the
    // same goes for a `ttl` outside `u32`.
    const rtype = model.RecordType.fromDb(stmt.columnText(2)) orelse return error.Mismatch;
    const ttl = std.math.cast(u32, stmt.columnInt(4)) orelse return error.Mismatch;
    const name = try stmt.columnTextAlloc(gpa, 1);
    errdefer gpa.free(name);
    const value = try stmt.columnTextAlloc(gpa, 3);
    errdefer gpa.free(value);
    return .{ .id = stmt.columnInt(0), .name = name, .rtype = rtype, .value = value, .ttl = ttl };
}

/// `error.Constraint`: `local_records` declares `UNIQUE(name, rtype, value)`, so
/// the same answer cannot be stored twice — a second TTL for one record would be
/// two truths.
pub fn insertLocalRecordRow(database: *db.Db, item: model.LocalRecord) db.Error!i64 {
    var stmt = try database.prepare(insert_local_record_sql);
    defer stmt.deinit();
    try stmt.bindText(1, item.name);
    try stmt.bindText(2, item.rtype.toDb());
    try stmt.bindText(3, item.value);
    try stmt.bindInt(4, item.ttl);
    try stmt.exec();
    return database.lastInsertRowid();
}

/// `error.NotFound`: no record holds `id`. `error.Constraint`:
/// `UNIQUE(name, rtype, value)`.
pub fn updateLocalRecord(database: *db.Db, id: i64, item: model.LocalRecord) db.Error!void {
    var stmt = try database.prepare(
        "UPDATE local_records SET name = ?2, rtype = ?3, value = ?4, ttl = ?5 WHERE id = ?1",
    );
    defer stmt.deinit();
    try stmt.bindInt(1, id);
    try stmt.bindText(2, item.name);
    try stmt.bindText(3, item.rtype.toDb());
    try stmt.bindText(4, item.value);
    try stmt.bindInt(5, item.ttl);
    return crud.execStrict(database, &stmt);
}

/// `error.NotFound`: no record holds `id`. Nothing references `local_records`,
/// so a delete cannot violate a constraint.
pub fn deleteLocalRecord(database: *db.Db, id: i64) db.Error!void {
    var stmt = try database.prepare("DELETE FROM local_records WHERE id = ?1");
    defer stmt.deinit();
    try stmt.bindInt(1, id);
    return crud.execStrict(database, &stmt);
}

pub const ForwardZoneRow = struct { id: i64, zone: []const u8, resolver: []const u8 };

/// Same order as `listForwardZones`; every string is a heap copy owned by `gpa`.
pub fn listForwardZoneRows(database: *db.Db, gpa: Allocator) db.Error!std.ArrayList(ForwardZoneRow) {
    return crud.listRows(
        ForwardZoneRow,
        database,
        gpa,
        "SELECT id, zone, resolver FROM forward_zones ORDER BY zone",
        readForwardZoneRow,
    );
}

pub fn freeForwardZoneRow(gpa: Allocator, row: ForwardZoneRow) void {
    crud.freeRow(ForwardZoneRow, gpa, row);
}

pub fn freeForwardZoneRows(gpa: Allocator, items: []const ForwardZoneRow) void {
    crud.freeRows(ForwardZoneRow, gpa, items);
}

pub fn getForwardZone(database: *db.Db, gpa: Allocator, id: i64) db.Error!?ForwardZoneRow {
    var stmt = try database.prepare("SELECT id, zone, resolver FROM forward_zones WHERE id = ?1");
    defer stmt.deinit();
    try stmt.bindInt(1, id);
    if (!try stmt.step()) return null;
    return try readForwardZoneRow(&stmt, gpa);
}

fn readForwardZoneRow(stmt: *db.Stmt, gpa: Allocator) db.Error!ForwardZoneRow {
    const zone = try stmt.columnTextAlloc(gpa, 1);
    errdefer gpa.free(zone);
    const resolver = try stmt.columnTextAlloc(gpa, 2);
    errdefer gpa.free(resolver);
    return .{ .id = stmt.columnInt(0), .zone = zone, .resolver = resolver };
}

/// `error.Constraint`: `forward_zones.zone` is UNIQUE — one zone has one
/// resolver.
pub fn insertForwardZoneRow(database: *db.Db, item: model.ForwardZone) db.Error!i64 {
    var stmt = try database.prepare("INSERT INTO forward_zones (zone, resolver) VALUES (?1, ?2)");
    defer stmt.deinit();
    try stmt.bindText(1, item.zone);
    try stmt.bindText(2, item.resolver);
    try stmt.exec();
    return database.lastInsertRowid();
}

/// `error.NotFound`: no zone holds `id`. `error.Constraint`:
/// `forward_zones.zone` is UNIQUE.
pub fn updateForwardZone(database: *db.Db, id: i64, item: model.ForwardZone) db.Error!void {
    var stmt = try database.prepare("UPDATE forward_zones SET zone = ?2, resolver = ?3 WHERE id = ?1");
    defer stmt.deinit();
    try stmt.bindInt(1, id);
    try stmt.bindText(2, item.zone);
    try stmt.bindText(3, item.resolver);
    return crud.execStrict(database, &stmt);
}

/// `error.NotFound`: no zone holds `id`. Nothing references `forward_zones`, so
/// a delete cannot violate a constraint.
pub fn deleteForwardZone(database: *db.Db, id: i64) db.Error!void {
    var stmt = try database.prepare("DELETE FROM forward_zones WHERE id = ?1");
    defer stmt.deinit();
    try stmt.bindInt(1, id);
    return crud.execStrict(database, &stmt);
}

// ---------------------------------------------------------------------------
// tests
// ---------------------------------------------------------------------------

const testing = std.testing;

fn openMigrated() !db.Db {
    var database = try db.Db.open(":memory:", .{ .mode = .memory });
    errdefer database.close();
    try db.applyPragmas(&database, .{});
    _ = try migrations.migrate(&database);
    return database;
}

fn seedLocalRecords(database: *db.Db) !void {
    const ctx: InsertContext = .{};
    try insertLocalRecord(database, .{
        .name = "nas.home.arpa",
        .rtype = .aaaa,
        .value = "fd00::5",
        .ttl = 60,
    }, ctx);
    try insertLocalRecord(database, .{
        .name = "nas.home.arpa",
        .rtype = .a,
        .value = "192.168.1.5",
    }, ctx);
    try insertLocalRecord(database, .{
        .name = "alias.home.arpa",
        .rtype = .cname,
        .value = "nas.home.arpa",
        .ttl = 120,
    }, ctx);
}

fn seedForwardZones(database: *db.Db) !void {
    const ctx: InsertContext = .{};
    try insertForwardZone(database, .{ .zone = "work.example", .resolver = "udp://10.0.0.1:53" }, ctx);
    try insertForwardZone(database, .{ .zone = "home.arpa", .resolver = "udp://192.168.1.1:53" }, ctx);
    try insertForwardZone(database, .{ .zone = "lab.example", .resolver = "tcp://[fd00::1]:53" }, ctx);
}

test "local_records round-trip in name, rtype, value order" {
    var database = try openMigrated();
    defer database.close();
    try seedLocalRecords(&database);

    var items = try listLocalRecords(&database, testing.allocator);
    defer items.deinit(testing.allocator);
    defer freeLocalRecords(testing.allocator, items.items);

    // `rtype` is compared as stored text, so 'A' sorts before 'AAAA'.
    try testing.expectEqual(@as(usize, 3), items.items.len);
    try testing.expectEqualStrings("alias.home.arpa", items.items[0].name);
    try testing.expectEqual(model.RecordType.cname, items.items[0].rtype);
    try testing.expectEqualStrings("nas.home.arpa", items.items[0].value);
    try testing.expectEqual(@as(u32, 120), items.items[0].ttl);
    try testing.expectEqualStrings("nas.home.arpa", items.items[1].name);
    try testing.expectEqual(model.RecordType.a, items.items[1].rtype);
    try testing.expectEqualStrings("192.168.1.5", items.items[1].value);
    try testing.expectEqual(@as(u32, 300), items.items[1].ttl);
    try testing.expectEqualStrings("nas.home.arpa", items.items[2].name);
    try testing.expectEqual(model.RecordType.aaaa, items.items[2].rtype);
    try testing.expectEqualStrings("fd00::5", items.items[2].value);
    try testing.expectEqual(@as(u32, 60), items.items[2].ttl);
}

test "deleteAllLocalRecords empties the table and countLocalRecords reflects it" {
    var database = try openMigrated();
    defer database.close();
    try seedLocalRecords(&database);

    try testing.expectEqual(@as(i64, 3), try countLocalRecords(&database));
    try deleteAllLocalRecords(&database);
    try testing.expectEqual(@as(i64, 0), try countLocalRecords(&database));
}

fn listLocalRecordsUnderFailure(gpa: Allocator) !void {
    var database = try openMigrated();
    defer database.close();
    try seedLocalRecords(&database);

    var items = try listLocalRecords(&database, gpa);
    defer items.deinit(gpa);
    defer freeLocalRecords(gpa, items.items);
}

test "listLocalRecords is leak-safe under allocation failure" {
    try testing.checkAllAllocationFailures(testing.allocator, listLocalRecordsUnderFailure, .{});
}

test "forward_zones round-trip in zone order" {
    var database = try openMigrated();
    defer database.close();
    try seedForwardZones(&database);

    var items = try listForwardZones(&database, testing.allocator);
    defer items.deinit(testing.allocator);
    defer freeForwardZones(testing.allocator, items.items);

    try testing.expectEqual(@as(usize, 3), items.items.len);
    try testing.expectEqualStrings("home.arpa", items.items[0].zone);
    try testing.expectEqualStrings("udp://192.168.1.1:53", items.items[0].resolver);
    try testing.expectEqualStrings("lab.example", items.items[1].zone);
    try testing.expectEqualStrings("tcp://[fd00::1]:53", items.items[1].resolver);
    try testing.expectEqualStrings("work.example", items.items[2].zone);
    try testing.expectEqualStrings("udp://10.0.0.1:53", items.items[2].resolver);
}

test "deleteAllForwardZones empties the table and countForwardZones reflects it" {
    var database = try openMigrated();
    defer database.close();
    try seedForwardZones(&database);

    try testing.expectEqual(@as(i64, 3), try countForwardZones(&database));
    try deleteAllForwardZones(&database);
    try testing.expectEqual(@as(i64, 0), try countForwardZones(&database));
}

fn listForwardZonesUnderFailure(gpa: Allocator) !void {
    var database = try openMigrated();
    defer database.close();
    try seedForwardZones(&database);

    var items = try listForwardZones(&database, gpa);
    defer items.deinit(gpa);
    defer freeForwardZones(gpa, items.items);
}

test "listForwardZones is leak-safe under allocation failure" {
    try testing.checkAllAllocationFailures(testing.allocator, listForwardZonesUnderFailure, .{});
}

// --- REST surface ----------------------------------------------------------

test "a local record round-trips through insert, get, list, update and delete" {
    var database = try openMigrated();
    defer database.close();

    const id = try insertLocalRecordRow(&database, .{
        .name = "nas.home.arpa",
        .rtype = .a,
        .value = "192.168.1.5",
    });

    const fetched = (try getLocalRecord(&database, testing.allocator, id)).?;
    defer freeLocalRecordRow(testing.allocator, fetched);
    try testing.expectEqual(id, fetched.id);
    try testing.expectEqualStrings("nas.home.arpa", fetched.name);
    try testing.expectEqual(model.RecordType.a, fetched.rtype);
    try testing.expectEqualStrings("192.168.1.5", fetched.value);
    try testing.expectEqual(@as(u32, 300), fetched.ttl);

    try updateLocalRecord(&database, id, .{
        .name = "nas.home.arpa",
        .rtype = .a,
        .value = "192.168.1.6",
        .ttl = 60,
    });
    const updated = (try getLocalRecord(&database, testing.allocator, id)).?;
    defer freeLocalRecordRow(testing.allocator, updated);
    try testing.expectEqualStrings("192.168.1.6", updated.value);
    try testing.expectEqual(@as(u32, 60), updated.ttl);

    var rows = try listLocalRecordRows(&database, testing.allocator);
    defer rows.deinit(testing.allocator);
    defer freeLocalRecordRows(testing.allocator, rows.items);
    try testing.expectEqual(@as(usize, 1), rows.items.len);
    try testing.expectEqual(id, rows.items[0].id);

    try deleteLocalRecord(&database, id);
    try testing.expectEqual(@as(?LocalRecordRow, null), try getLocalRecord(&database, testing.allocator, id));
    try testing.expectEqual(@as(i64, 0), try countLocalRecords(&database));
}

test "local record update and delete report NotFound for an id no row holds" {
    var database = try openMigrated();
    defer database.close();

    const item: model.LocalRecord = .{ .name = "x.home.arpa", .rtype = .a, .value = "10.0.0.1" };
    try testing.expectError(error.NotFound, updateLocalRecord(&database, 404, item));
    try testing.expectError(error.NotFound, deleteLocalRecord(&database, 404));
    try testing.expectEqual(@as(?LocalRecordRow, null), try getLocalRecord(&database, testing.allocator, 404));
}

test "a duplicate name, rtype and value surfaces as error.Constraint" {
    var database = try openMigrated();
    defer database.close();

    const first: model.LocalRecord = .{ .name = "nas.home.arpa", .rtype = .a, .value = "192.168.1.5" };
    _ = try insertLocalRecordRow(&database, first);
    // The TTL is not part of the UNIQUE key, so a second TTL is still a clash.
    try testing.expectError(error.Constraint, insertLocalRecordRow(&database, .{
        .name = "nas.home.arpa",
        .rtype = .a,
        .value = "192.168.1.5",
        .ttl = 60,
    }));

    const other = try insertLocalRecordRow(&database, .{
        .name = "nas.home.arpa",
        .rtype = .aaaa,
        .value = "fd00::5",
    });
    try testing.expectError(error.Constraint, updateLocalRecord(&database, other, first));
    try testing.expectEqual(@as(i64, 2), try countLocalRecords(&database));
}

test "a forward zone round-trips through insert, get, list, update and delete" {
    var database = try openMigrated();
    defer database.close();

    const id = try insertForwardZoneRow(&database, .{
        .zone = "home.arpa",
        .resolver = "udp://192.168.1.1:53",
    });

    const fetched = (try getForwardZone(&database, testing.allocator, id)).?;
    defer freeForwardZoneRow(testing.allocator, fetched);
    try testing.expectEqual(id, fetched.id);
    try testing.expectEqualStrings("home.arpa", fetched.zone);
    try testing.expectEqualStrings("udp://192.168.1.1:53", fetched.resolver);

    try updateForwardZone(&database, id, .{ .zone = "lab.example", .resolver = "tcp://[fd00::1]:53" });
    const updated = (try getForwardZone(&database, testing.allocator, id)).?;
    defer freeForwardZoneRow(testing.allocator, updated);
    try testing.expectEqualStrings("lab.example", updated.zone);
    try testing.expectEqualStrings("tcp://[fd00::1]:53", updated.resolver);

    var rows = try listForwardZoneRows(&database, testing.allocator);
    defer rows.deinit(testing.allocator);
    defer freeForwardZoneRows(testing.allocator, rows.items);
    try testing.expectEqual(@as(usize, 1), rows.items.len);
    try testing.expectEqual(id, rows.items[0].id);

    try deleteForwardZone(&database, id);
    try testing.expectEqual(@as(?ForwardZoneRow, null), try getForwardZone(&database, testing.allocator, id));
    try testing.expectEqual(@as(i64, 0), try countForwardZones(&database));
}

test "forward zone update and delete report NotFound for an id no row holds" {
    var database = try openMigrated();
    defer database.close();

    const item: model.ForwardZone = .{ .zone = "home.arpa", .resolver = "udp://10.0.0.1:53" };
    try testing.expectError(error.NotFound, updateForwardZone(&database, 404, item));
    try testing.expectError(error.NotFound, deleteForwardZone(&database, 404));
    try testing.expectEqual(@as(?ForwardZoneRow, null), try getForwardZone(&database, testing.allocator, 404));
}

test "a duplicate zone surfaces as error.Constraint on insert and on update" {
    var database = try openMigrated();
    defer database.close();

    _ = try insertForwardZoneRow(&database, .{ .zone = "home.arpa", .resolver = "udp://10.0.0.1:53" });
    const other = try insertForwardZoneRow(&database, .{ .zone = "lab.example", .resolver = "udp://10.0.0.2:53" });

    try testing.expectError(error.Constraint, insertForwardZoneRow(&database, .{
        .zone = "home.arpa",
        .resolver = "udp://10.0.0.3:53",
    }));
    try testing.expectError(error.Constraint, updateForwardZone(&database, other, .{
        .zone = "home.arpa",
        .resolver = "udp://10.0.0.2:53",
    }));
    try testing.expectEqual(@as(i64, 2), try countForwardZones(&database));
}

fn localRowsUnderFailure(gpa: Allocator) !void {
    var database = try openMigrated();
    defer database.close();
    try seedLocalRecords(&database);
    try seedForwardZones(&database);

    var records = try listLocalRecordRows(&database, gpa);
    defer records.deinit(gpa);
    defer freeLocalRecordRows(gpa, records.items);
    const record = (try getLocalRecord(&database, gpa, records.items[0].id)).?;
    defer freeLocalRecordRow(gpa, record);

    var zones = try listForwardZoneRows(&database, gpa);
    defer zones.deinit(gpa);
    defer freeForwardZoneRows(gpa, zones.items);
    const zone = (try getForwardZone(&database, gpa, zones.items[0].id)).?;
    defer freeForwardZoneRow(gpa, zone);
}

test "the local read surface is leak-safe under allocation failure" {
    try testing.checkAllAllocationFailures(testing.allocator, localRowsUnderFailure, .{});
}