-- Test for bd-y1n / ra6 3b: C-side scalar encode.
--
-- Only runs when PB_ENABLE_C=1 is set in the environment AND the C
-- runtime module is loadable. Otherwise the group is skipped, which
-- keeps `just test` green on hosts without the C module built.
--
-- Acceptance per bd-y1n:
--   Person encode for {name='x', age=42, balance=-7, user_id=...,
--   weight_kg=3.14} byte-equal to mode=full pure-Lua output.

local t = require('luatest')
local ffi = require('ffi')

local pb = require('pb')
local c_runtime = pb.c_runtime

local function skip_if_no_c()
    if c_runtime == nil then
        t.skip('PB_ENABLE_C not set or pb.c_runtime not available')
    end
end

-- The mode=full reference is the byte-equality target; the test runs
-- against both codegen modes' descriptors (the C plan is mode-agnostic).
local full_hello

for _, mode in ipairs({'full', 'runtime'}) do
    local g = t.group('c_runtime_encode.' .. mode)
    local hello

    g.before_all(function()
        skip_if_no_c()
        hello = require(mode .. '.hello.hello_pb')
        full_hello = require('full.hello.hello_pb')
    end)

    g.before_each(skip_if_no_c)

    -- ---------- Acceptance per bd-y1n ----------

    function g.test_acceptance_person_scalar_subset()
        local msg = {
            name = 'x',
            age = 42,
            balance = -7,
            user_id = 0xDEADBEEFCAFEBABEULL,
            weight_kg = 3.14,
        }
        local plan = c_runtime.compile_plan(hello.Person_descriptor)
        local c_bytes = c_runtime.encode(plan, msg)
        local lua_bytes = full_hello.Person_encode(msg)
        t.assert_equals(c_bytes, lua_bytes,
            'C encode matches mode=full pure-Lua encode byte-for-byte')
    end

    -- ---------- Per-kind coverage ----------

    function g.test_empty_message_produces_empty_string()
        local plan = c_runtime.compile_plan(hello.Address_descriptor)
        t.assert_equals(c_runtime.encode(plan, {}), '')
    end

    function g.test_address_strings_and_int32()
        local plan = c_runtime.compile_plan(hello.Address_descriptor)
        local msg = {street = 'Main', city = 'Springfield', zip = 12345}
        t.assert_equals(c_runtime.encode(plan, msg),
                        full_hello.Address_encode(msg))
    end

    function g.test_proto3_optional_emits_empty_string()
        -- Address.apartment is proto3-optional; presence beats default.
        local plan = c_runtime.compile_plan(hello.Address_descriptor)
        local msg = {apartment = ''}
        t.assert_equals(c_runtime.encode(plan, msg),
                        full_hello.Address_encode(msg))
    end

    function g.test_double_negative_zero_emits()
        local plan = c_runtime.compile_plan(hello.Person_descriptor)
        -- +0.0 -> skip; -0.0 -> emit (sign bit preserved by wire spec).
        local m_pos = {weight_kg = 0.0}
        local m_neg = {weight_kg = -0.0}
        t.assert_equals(c_runtime.encode(plan, m_pos),
                        full_hello.Person_encode(m_pos))
        t.assert_equals(c_runtime.encode(plan, m_neg),
                        full_hello.Person_encode(m_neg))
    end

    function g.test_enum_as_number()
        local plan = c_runtime.compile_plan(hello.Person_descriptor)
        local msg = {status = 2}  -- ERROR
        t.assert_equals(c_runtime.encode(plan, msg),
                        full_hello.Person_encode(msg))
    end

    function g.test_enum_as_string_lookup()
        local plan = c_runtime.compile_plan(hello.Person_descriptor)
        local msg = {status = 'OK'}
        t.assert_equals(c_runtime.encode(plan, msg),
                        full_hello.Person_encode(msg))
    end

    function g.test_enum_zero_value_suppressed()
        local plan = c_runtime.compile_plan(hello.Person_descriptor)
        local msg = {status = 'UNKNOWN'}  -- = 0; default-suppressed
        t.assert_equals(c_runtime.encode(plan, msg), '')
    end

    function g.test_enum_unknown_string_errors()
        local plan = c_runtime.compile_plan(hello.Person_descriptor)
        t.assert_error_msg_contains("unknown enum value 'NOPE'", function()
            c_runtime.encode(plan, {status = 'NOPE'})
        end)
    end

    function g.test_fixed64_cdata_round_trip()
        local plan = c_runtime.compile_plan(hello.Person_descriptor)
        local msg = {user_id = ffi.new('uint64_t', 0x123456789ABCDEF0)}
        t.assert_equals(c_runtime.encode(plan, msg),
                        full_hello.Person_encode(msg))
    end

    function g.test_sint32_negative_and_zero()
        local plan = c_runtime.compile_plan(hello.Person_descriptor)
        t.assert_equals(c_runtime.encode(plan, {balance = 0}), '')
        t.assert_equals(
            c_runtime.encode(plan, {balance = -1}),
            full_hello.Person_encode({balance = -1}))
        t.assert_equals(
            c_runtime.encode(plan, {balance = 0x7fffffff}),
            full_hello.Person_encode({balance = 0x7fffffff}))
    end

    function g.test_int32_zero_suppressed()
        local plan = c_runtime.compile_plan(hello.Person_descriptor)
        t.assert_equals(c_runtime.encode(plan, {age = 0}), '')
    end

    function g.test_bytes_field()
        -- Person.avatar is bytes @8
        local plan = c_runtime.compile_plan(hello.Person_descriptor)
        local msg = {avatar = '\x00\x01\xff\xfe'}
        t.assert_equals(c_runtime.encode(plan, msg),
                        full_hello.Person_encode(msg))
    end

    function g.test_skips_repeated_and_map_fields()
        -- 3d scope: singular message now encoded. Repeated and map
        -- are still silently skipped — 3e/3h will replace this.
        local plan = c_runtime.compile_plan(hello.Person_descriptor)
        local msg = {
            name = 'x',
            emails = {'a@b'},                 -- repeated string (skip)
            address = {street = 'Main'},      -- message (encode)
            lucky_numbers = {1, 2, 3},        -- repeated packed (skip)
            ages_by_nickname = {alice = 30},  -- map (skip)
        }
        local expected = full_hello.Person_encode(
            {name = 'x', address = {street = 'Main'}})
        t.assert_equals(c_runtime.encode(plan, msg), expected)
    end

    -- ---------- Sub-message encode (bd-hwe / ra6 3d) ----------

    function g.test_singular_submessage_round_trip()
        -- Person.address (one-level singular sub-message) round-trip.
        local plan = c_runtime.compile_plan(hello.Person_descriptor)
        local msg = {
            name = 'x',
            address = {street = 'Main', city = 'Springfield', zip = 100},
        }
        t.assert_equals(c_runtime.encode(plan, msg),
                        full_hello.Person_encode(msg))
    end

    function g.test_empty_submessage_emits_tag_with_zero_length()
        -- Singular sub-message with an empty table — proto3 presence
        -- semantics require emitting tag + length(0). The Lua codec
        -- does this; the C codec must match.
        local plan = c_runtime.compile_plan(hello.Person_descriptor)
        local msg = {name = 'x', address = {}}
        t.assert_equals(c_runtime.encode(plan, msg),
                        full_hello.Person_encode(msg))
    end

    function g.test_submessage_with_proto3_optional_field()
        -- Address.apartment is proto3-optional. Encode through the
        -- sub-message must surface the empty string just like the
        -- top-level Address codec does.
        local plan = c_runtime.compile_plan(hello.Person_descriptor)
        local msg = {address = {apartment = ''}}
        t.assert_equals(c_runtime.encode(plan, msg),
                        full_hello.Person_encode(msg))
    end

    function g.test_submessage_non_table_value_errors()
        local plan = c_runtime.compile_plan(hello.Person_descriptor)
        t.assert_error_msg_contains('table', function()
            c_runtime.encode(plan, {address = 'not a table'})
        end)
    end

    function g.test_nested_5_levels()
        -- 5-level chain of singular sub-messages. Exercises the
        -- recursion depth and the cycle-breaking c_plan stash.
        local cn = require(mode .. '.c_nested.c_nested_pb')
        local full_cn = require('full.c_nested.c_nested_pb')
        local msg = {
            v = 1,
            next = {v = 2, next = {v = 3, next = {v = 4,
                next = {v = 5}}}},
        }
        local plan = c_runtime.compile_plan(cn.L1_descriptor)
        t.assert_equals(c_runtime.encode(plan, msg),
                        full_cn.L1_encode(msg))
    end

    function g.test_large_submessage_triggers_parent_grow()
        -- Parent buffer starts at 4KB stack-backed; force a parent
        -- regrow path during the post-recursion ebuf_reserve by
        -- packing a >4KB string into the sub-message.
        local plan = c_runtime.compile_plan(hello.Person_descriptor)
        local msg = {
            name = 'x',
            address = {street = string.rep('s', 8192)},
        }
        t.assert_equals(c_runtime.encode(plan, msg),
                        full_hello.Person_encode(msg))
    end

    function g.test_long_string_grows_buffer()
        -- Stack buffer is 4KB; force the heap-promotion path with a
        -- string that pushes past it.
        local plan = c_runtime.compile_plan(hello.Person_descriptor)
        local msg = {name = string.rep('a', 8192)}
        t.assert_equals(c_runtime.encode(plan, msg),
                        full_hello.Person_encode(msg))
    end

    function g.test_wkt_override_rejected()
        -- has_override plans skip field-walk; 3b does not handle them.
        local plan = c_runtime.compile_plan(pb.wkt.Timestamp_descriptor)
        t.assert_error_msg_contains('override', function()
            c_runtime.encode(plan, {seconds = 1})
        end)
    end
end