
CONTENTS
========

1. Default build
2. Using freeciv built with AI-modules support
3. Building freeciv with AI-modules support
4. Coding new AI module
5. Using default AI as part of new AI module
6. Callback interface ChangeLog


1. Default build
----------------

By default Freeciv is built with just one, "classic", AI type
statically built in, and with no support for dynamic AI modules.
Classic AI is always used for all players, effectively hiding the
fact that AI module interface even exist.


2. Using freeciv built with AI-modules support
----------------------------------------------

Some modules might be statically linked to freeciv server, and those
are always available. If freeciv is built with also dynamic modules
support enabled, one can load additional AI modules to server with
commandline option "--LoadAI <modulename>"
Whether module is statically linked or dynamically loaded, new AI players
that use that module can be created by giving "create" command AI type as
second parameter
> create Leonidas classic

Players created any other way, such as by aifill will get the AI type
that has been made the default freeciv build time.

Information "list" command shows includes player's AI type:
> list
Leonidas [#ff0000]: Team 0, user Unassigned
  AI, classic, difficulty level Easy


3. Building freeciv with AI-modules support
-------------------------------------------

There's three configure options controlling AI-modules support to be
built in to freeciv.

To statically link some of the supplied AI modules to freeciv,
use --enable-ai-static=<comma,separated,list>. Default value for this
is just "classic". Order of the modules is important in that first of
the modules will be the default AI type used for all the players for whom
it's not explicitly set.

To support dynamically loading additional modules, use
--enable-aimodules. It requires that also --enable-shared has been used,
which may not work on all platforms.
Special value --enable-aimodules=experimental makes freeciv also to build
all the modules in its source tree as dynamically loadable AI modules.

In case you want to use some dynamically loadable module as the default
AI type instead of first type listed for --enable-ai-static, you can
explicitly set the default type with --with-default-ai=<type>.

Dynamic AI modules are expected in their correct installation location
unless one has configured with --enable-debug which allows freeciv
server to look for supplied modules from build directory too. Otherwise you
cannot use dynamic modules from the freeciv build dir, but you need
to "make install" freeciv to install them to correct location.


4. Coding new dynamic AI module
-------------------------------

Dynamic AI module to be loaded with "--LoadAI <modulename>" needs to contain
two functions.

const char *fc_ai_<modulename>_capstr(void)
  This needs to return capability string of the module. This is used to
  check if module is compatible with the version of freeciv one tries to
  load it into. Current freeciv's capstr is in common/ai.h macro FC_AI_MOD_CAPSTR.

 
bool fc_ai_<modulename>_setup(struct ai_type *ai)
  This function is called for AI module to setup itself. Most importantly
  it should setup callback table ai->funcs so that its other functions
  get called, and fill ai->name so that it can be referred to in creation of
  new players.
  Callback table, with comments when each callback gets called, is defined
  in common/ai.h

For "--LoadAI <modulename>" to find the AI module, it must reside in ${libdir}/fcai/
(/usr/lib/fcai by default) under name fc_ai_<modulename>.so


5. Using default AI as part of new AI module
--------------------------------------------

Default AI here refers to specific code module that any AI module can use, not to any
one AI module. Classic AI module is just a thin wrapper around it, and also Threaded AI
uses it.

Almost all functions in default AI API take pointer to current AI type as parameter.
This is used for accessing memory associated with the correct AI type from the structures
having such AI type specific data.

If a AI type wants to add its own data associated with some code structure, it needs
to make sure data needed by default AI is in the beginning of the allocated data blocks.
For example, see threaded AI: tai_player_alloc(), tai_player_free(), and struct tai_plr.

Default AI code is usually built in freeciv only if some AI type using it has been built;
either 'classic' or 'threaded'. If no such ai type has been built, you can still force
it in for custom ai types to use by passing configure option --with-ai-lib


6. Callback interface ChangeLog
-------------------------------

New in Freeciv 2.6:
-------------------
- Renamed enum danger_consideration as enum override_bool
- Added restart_phase, called when AI gains control of the player whose phase is already
  active, for example when continuing from a saved game
- Added created_by_civil_war, called for AI type of the player who got created from
  civil war
- Added "created" player parameter to split_by_civil_war
- Added game_start, called for all AI types when game starts
- "city_got" is called when the city is fully initialized, "city_lost" when city still valid
- Added gov_value for giving AI control of deciding value of governments
- Added player_save_relations and player_load_relations called on savegame handling for a
  player once per other player in game. Old player_save and player_load are called only once
  overall
- Added want_to_explore, called for AI type of the unit owner, when it is about to autoexplore
- Added currently unused 'reserved' pointers that we can populate with optional callbacks
  without need to change the mandatory capability of the modules
