-module(gleeth@gas).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/gleeth/gas.gleam").
-export([estimate_legacy/5, estimate_eip1559/5]).
-export_type([legacy_gas_estimate/0, eip1559_gas_estimate/0]).

-if(?OTP_RELEASE >= 27).
-define(MODULEDOC(Str), -moduledoc(Str)).
-define(DOC(Str), -doc(Str)).
-else.
-define(MODULEDOC(Str), -compile([])).
-define(DOC(Str), -compile([])).
-endif.

?MODULEDOC(
    " Gas estimation helpers for legacy and EIP-1559 transactions.\n"
    "\n"
    " These functions combine multiple RPC calls to produce a complete\n"
    " gas estimate that can be passed directly to a transaction builder.\n"
).

-type legacy_gas_estimate() :: {legacy_gas_estimate, binary(), binary()}.

-type eip1559_gas_estimate() :: {eip1559_gas_estimate,
        binary(),
        binary(),
        binary()}.

-file("src/gleeth/gas.gleam", 28).
?DOC(" Estimate gas for a legacy transaction by fetching gas price and gas limit.\n").
-spec estimate_legacy(
    gleeth@provider:provider(),
    binary(),
    binary(),
    binary(),
    binary()
) -> {ok, legacy_gas_estimate()} | {error, gleeth@rpc@types:gleeth_error()}.
estimate_legacy(Provider, From, To, Value, Data) ->
    gleam@result:'try'(
        gleeth@rpc@methods:get_gas_price(Provider),
        fun(Gas_price) ->
            gleam@result:'try'(
                gleeth@rpc@methods:estimate_gas(Provider, From, To, Value, Data),
                fun(Gas_limit) ->
                    {ok, {legacy_gas_estimate, Gas_price, Gas_limit}}
                end
            )
        end
    ).

-file("src/gleeth/gas.gleam", 49).
?DOC(
    " Estimate gas for an EIP-1559 transaction by fetching priority fee,\n"
    " base fee from fee history, and gas limit.\n"
    " Computes max_fee = 2 * base_fee + priority_fee.\n"
).
-spec estimate_eip1559(
    gleeth@provider:provider(),
    binary(),
    binary(),
    binary(),
    binary()
) -> {ok, eip1559_gas_estimate()} | {error, gleeth@rpc@types:gleeth_error()}.
estimate_eip1559(Provider, From, To, Value, Data) ->
    gleam@result:'try'(
        gleeth@rpc@methods:get_max_priority_fee(Provider),
        fun(Priority_fee) ->
            gleam@result:'try'(
                gleeth@rpc@methods:get_fee_history(
                    Provider,
                    1,
                    <<"latest"/utf8>>,
                    []
                ),
                fun(Fee_history) ->
                    gleam@result:'try'(
                        gleeth@rpc@methods:estimate_gas(
                            Provider,
                            From,
                            To,
                            Value,
                            Data
                        ),
                        fun(Gas_limit) ->
                            gleam@result:'try'(
                                begin
                                    _pipe = gleam@list:last(
                                        erlang:element(3, Fee_history)
                                    ),
                                    gleam@result:map_error(
                                        _pipe,
                                        fun(_) ->
                                            {parse_error,
                                                <<"Fee history returned empty base_fee_per_gas"/utf8>>}
                                        end
                                    )
                                end,
                                fun(Base_fee_hex) ->
                                    gleam@result:'try'(
                                        begin
                                            _pipe@1 = gleeth@utils@hex:to_int(
                                                Base_fee_hex
                                            ),
                                            gleam@result:map_error(
                                                _pipe@1,
                                                fun(_) ->
                                                    {parse_error,
                                                        <<"Failed to parse base fee hex: "/utf8,
                                                            Base_fee_hex/binary>>}
                                                end
                                            )
                                        end,
                                        fun(Base_fee_int) ->
                                            gleam@result:'try'(
                                                begin
                                                    _pipe@2 = gleeth@utils@hex:to_int(
                                                        Priority_fee
                                                    ),
                                                    gleam@result:map_error(
                                                        _pipe@2,
                                                        fun(_) ->
                                                            {parse_error,
                                                                <<"Failed to parse priority fee hex: "/utf8,
                                                                    Priority_fee/binary>>}
                                                        end
                                                    )
                                                end,
                                                fun(Priority_fee_int) ->
                                                    Max_fee_int = (2 * Base_fee_int)
                                                    + Priority_fee_int,
                                                    Max_fee_hex = gleeth@utils@hex:from_int(
                                                        Max_fee_int
                                                    ),
                                                    {ok,
                                                        {eip1559_gas_estimate,
                                                            Max_fee_hex,
                                                            Priority_fee,
                                                            Gas_limit}}
                                                end
                                            )
                                        end
                                    )
                                end
                            )
                        end
                    )
                end
            )
        end
    ).