//! `upstreams`.
//!
//! The list sorts by `priority` first because that is the operationally
//! meaningful order — it matches what `Pool.init` expects — and `url` breaks
//! ties uniquely, which is what makes an export byte-stable.
//!
//! The import path is list / insert / deleteAll / count. Phase 8's REST surface
//! is the second half of this file: it speaks row ids, because that is what an
//! `/api/upstreams/{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;

/// Every string in the result is a heap copy owned by `gpa`.
pub fn listUpstreams(database: *db.Db, gpa: Allocator) db.Error!std.ArrayList(model.UpstreamServer) {
    var stmt = try database.prepare(
        "SELECT url, priority, enabled, tls_name FROM upstreams ORDER BY priority, url",
    );
    defer stmt.deinit();

    var out: std.ArrayList(model.UpstreamServer) = .empty;
    // `errdefer`s run in reverse: the free pass is declared last so it runs
    // before the backing array is released.
    errdefer out.deinit(gpa);
    errdefer freeUpstreams(gpa, out.items);

    while (try stmt.step()) {
        const url = try stmt.columnTextAlloc(gpa, 0);
        errdefer gpa.free(url);
        const priority = std.math.cast(i32, stmt.columnInt(1)) orelse return error.Mismatch;
        const tls_name = try stmt.columnTextAlloc(gpa, 3);
        errdefer gpa.free(tls_name);
        try out.append(gpa, .{
            .url = url,
            .priority = priority,
            .enabled = stmt.columnBool(2),
            .tls_name = tls_name,
        });
    }
    return out;
}

pub fn freeUpstreams(gpa: Allocator, items: []const model.UpstreamServer) void {
    for (items) |item| {
        gpa.free(item.url);
        gpa.free(item.tls_name);
    }
}

pub fn insertUpstream(database: *db.Db, item: model.UpstreamServer, ctx: InsertContext) db.Error!void {
    _ = ctx;
    var stmt = try database.prepare(
        "INSERT INTO upstreams (url, priority, enabled, tls_name) VALUES (?1, ?2, ?3, ?4)",
    );
    defer stmt.deinit();
    try stmt.bindText(1, item.url);
    try stmt.bindInt(2, item.priority);
    try stmt.bindBool(3, item.enabled);
    try stmt.bindText(4, item.tls_name);
    try stmt.exec();
}

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

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

// ---------------------------------------------------------------------------
// REST surface (milestone 8)
// ---------------------------------------------------------------------------
//
// The write shape is `model.UpstreamServer`: its four fields are exactly the
// columns of the table, so the REST layer needs no second shape for them.

pub const UpstreamRow = struct {
    id: i64,
    url: []const u8,
    priority: i32,
    enabled: bool,
    tls_name: []const u8,
};

const list_upstream_rows_sql =
    \\SELECT id, url, priority, enabled, tls_name FROM upstreams ORDER BY priority, url
;

const get_upstream_sql =
    \\SELECT id, url, priority, enabled, tls_name FROM upstreams WHERE id = ?1
;

/// Same order as `listUpstreams`; every string is a heap copy owned by `gpa`.
pub fn listUpstreamRows(database: *db.Db, gpa: Allocator) db.Error!std.ArrayList(UpstreamRow) {
    var stmt = try database.prepare(list_upstream_rows_sql);
    defer stmt.deinit();

    var out: std.ArrayList(UpstreamRow) = .empty;
    errdefer out.deinit(gpa);
    errdefer freeUpstreamRows(gpa, out.items);

    while (try stmt.step()) {
        const row = try readUpstreamRow(&stmt, gpa);
        errdefer freeUpstreamRow(gpa, row);
        try out.append(gpa, row);
    }
    return out;
}

pub fn freeUpstreamRow(gpa: Allocator, row: UpstreamRow) void {
    gpa.free(row.url);
    gpa.free(row.tls_name);
}

pub fn freeUpstreamRows(gpa: Allocator, items: []const UpstreamRow) void {
    for (items) |item| freeUpstreamRow(gpa, item);
}

pub fn getUpstream(database: *db.Db, gpa: Allocator, id: i64) db.Error!?UpstreamRow {
    var stmt = try database.prepare(get_upstream_sql);
    defer stmt.deinit();
    try stmt.bindInt(1, id);
    if (!try stmt.step()) return null;
    return try readUpstreamRow(&stmt, gpa);
}

fn readUpstreamRow(stmt: *db.Stmt, gpa: Allocator) db.Error!UpstreamRow {
    const url = try stmt.columnTextAlloc(gpa, 1);
    errdefer gpa.free(url);
    const tls_name = try stmt.columnTextAlloc(gpa, 4);
    errdefer gpa.free(tls_name);
    // The column is a 64-bit integer; the row field is `i32`. A value outside
    // that range means something other than nxdns wrote the row.
    const priority = std.math.cast(i32, stmt.columnInt(2)) orelse return error.Mismatch;
    return .{
        .id = stmt.columnInt(0),
        .url = url,
        .priority = priority,
        .enabled = stmt.columnBool(3),
        .tls_name = tls_name,
    };
}

/// `error.Constraint`: `upstreams.url` is UNIQUE.
pub fn insertUpstreamRow(database: *db.Db, item: model.UpstreamServer) db.Error!i64 {
    var stmt = try database.prepare(
        "INSERT INTO upstreams (url, priority, enabled, tls_name) VALUES (?1, ?2, ?3, ?4)",
    );
    defer stmt.deinit();
    try stmt.bindText(1, item.url);
    try stmt.bindInt(2, item.priority);
    try stmt.bindBool(3, item.enabled);
    try stmt.bindText(4, item.tls_name);
    try stmt.exec();
    return database.lastInsertRowid();
}

/// `error.NotFound`: no upstream holds `id`. `error.Constraint`:
/// `upstreams.url` is UNIQUE.
pub fn updateUpstream(database: *db.Db, id: i64, item: model.UpstreamServer) db.Error!void {
    var stmt = try database.prepare(
        "UPDATE upstreams SET url = ?2, priority = ?3, enabled = ?4, tls_name = ?5 WHERE id = ?1",
    );
    defer stmt.deinit();
    try stmt.bindInt(1, id);
    try stmt.bindText(2, item.url);
    try stmt.bindInt(3, item.priority);
    try stmt.bindBool(4, item.enabled);
    try stmt.bindText(5, item.tls_name);
    return crud.execStrict(database, &stmt);
}

/// `error.NotFound`: no upstream holds `id`. Nothing references `upstreams`, so
/// a delete cannot violate a constraint.
pub fn deleteUpstream(database: *db.Db, id: i64) db.Error!void {
    var stmt = try database.prepare("DELETE FROM upstreams 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 seedUpstreams(database: *db.Db) !void {
    const ctx: InsertContext = .{};
    try insertUpstream(database, .{ .url = "https://dns.example/dns-query", .priority = 50 }, ctx);
    try insertUpstream(database, .{
        .url = "tls://1.1.1.1:853",
        .priority = 10,
        .enabled = false,
        .tls_name = "one.one.one.one",
    }, ctx);
    try insertUpstream(database, .{ .url = "https://a.example/dns-query", .priority = 50 }, ctx);
}

test "upstreams round-trip in priority then url order" {
    var database = try openMigrated();
    defer database.close();
    try seedUpstreams(&database);

    var items = try listUpstreams(&database, testing.allocator);
    defer items.deinit(testing.allocator);
    defer freeUpstreams(testing.allocator, items.items);

    try testing.expectEqual(@as(usize, 3), items.items.len);
    try testing.expectEqualStrings("tls://1.1.1.1:853", items.items[0].url);
    try testing.expectEqual(@as(i32, 10), items.items[0].priority);
    try testing.expect(!items.items[0].enabled);
    try testing.expectEqualStrings("one.one.one.one", items.items[0].tls_name);
    try testing.expectEqualStrings("https://a.example/dns-query", items.items[1].url);
    // An upstream inserted without one reads back as the empty column default.
    try testing.expectEqualStrings("", items.items[1].tls_name);
    try testing.expectEqual(@as(i32, 50), items.items[1].priority);
    try testing.expect(items.items[1].enabled);
    try testing.expectEqualStrings("https://dns.example/dns-query", items.items[2].url);
    try testing.expectEqual(@as(i32, 50), items.items[2].priority);
    try testing.expect(items.items[2].enabled);
}

test "deleteAllUpstreams empties the table and countUpstreams reflects it" {
    var database = try openMigrated();
    defer database.close();
    try seedUpstreams(&database);

    try testing.expectEqual(@as(i64, 3), try countUpstreams(&database));
    try deleteAllUpstreams(&database);
    try testing.expectEqual(@as(i64, 0), try countUpstreams(&database));

    var items = try listUpstreams(&database, testing.allocator);
    defer items.deinit(testing.allocator);
    defer freeUpstreams(testing.allocator, items.items);
    try testing.expectEqual(@as(usize, 0), items.items.len);
}

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

    var items = try listUpstreams(&database, gpa);
    defer items.deinit(gpa);
    defer freeUpstreams(gpa, items.items);
}

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

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

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

    const id = try insertUpstreamRow(&database, .{
        .url = "tls://1.1.1.1:853",
        .priority = 10,
        .tls_name = "one.one.one.one",
    });

    const fetched = (try getUpstream(&database, testing.allocator, id)).?;
    defer freeUpstreamRow(testing.allocator, fetched);
    try testing.expectEqual(id, fetched.id);
    try testing.expectEqualStrings("tls://1.1.1.1:853", fetched.url);
    try testing.expectEqual(@as(i32, 10), fetched.priority);
    try testing.expect(fetched.enabled);
    try testing.expectEqualStrings("one.one.one.one", fetched.tls_name);

    const second = try insertUpstreamRow(&database, .{ .url = "udp://9.9.9.9:53", .priority = 20 });

    var rows = try listUpstreamRows(&database, testing.allocator);
    defer rows.deinit(testing.allocator);
    defer freeUpstreamRows(testing.allocator, rows.items);
    try testing.expectEqual(@as(usize, 2), rows.items.len);
    try testing.expectEqual(id, rows.items[0].id);
    try testing.expectEqual(second, rows.items[1].id);
    try testing.expectEqualStrings("", rows.items[1].tls_name);

    try updateUpstream(&database, id, .{
        .url = "tls://1.0.0.1:853",
        .priority = 5,
        .enabled = false,
        .tls_name = "",
    });
    const updated = (try getUpstream(&database, testing.allocator, id)).?;
    defer freeUpstreamRow(testing.allocator, updated);
    try testing.expectEqualStrings("tls://1.0.0.1:853", updated.url);
    try testing.expectEqual(@as(i32, 5), updated.priority);
    try testing.expect(!updated.enabled);
    try testing.expectEqualStrings("", updated.tls_name);

    try deleteUpstream(&database, id);
    try testing.expectEqual(@as(?UpstreamRow, null), try getUpstream(&database, testing.allocator, id));
    try testing.expectEqual(@as(i64, 1), try countUpstreams(&database));
}

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

    try testing.expectError(error.NotFound, updateUpstream(&database, 404, .{ .url = "udp://9.9.9.9:53" }));
    try testing.expectError(error.NotFound, deleteUpstream(&database, 404));
    try testing.expectEqual(@as(?UpstreamRow, null), try getUpstream(&database, testing.allocator, 404));
}

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

    _ = try insertUpstreamRow(&database, .{ .url = "udp://9.9.9.9:53" });
    const other = try insertUpstreamRow(&database, .{ .url = "udp://1.1.1.1:53" });

    try testing.expectError(error.Constraint, insertUpstreamRow(&database, .{ .url = "udp://9.9.9.9:53" }));
    try testing.expectError(error.Constraint, updateUpstream(&database, other, .{ .url = "udp://9.9.9.9:53" }));
    try testing.expectEqual(@as(i64, 2), try countUpstreams(&database));
}

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

    var rows = try listUpstreamRows(&database, gpa);
    defer rows.deinit(gpa);
    defer freeUpstreamRows(gpa, rows.items);

    const one = (try getUpstream(&database, gpa, rows.items[0].id)).?;
    defer freeUpstreamRow(gpa, one);
}

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