/*
** 2024-09-23
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** This app's single purpose is to emit parts of the Makefile code for
** building sqlite3's WASM build. The main motivation is to generate
** code which "can" be created via GNU Make's eval command but is
** highly illegible when constructed that way. Attempts to write this
** app in Bash and TCL have suffered from the problem that both
** require escaping $ symbols, making the resulting script code as
** illegible as the eval spaghetti we want to get away from. Writing
** it in C is, somewhat surprisingly, _slightly_ less illegible than
** writing it in bash, tcl, or native Make code.
**
** The emitted makefile code is not standalone - it depends on
** variables and $(call)able functions from the main makefile.
**
*/

#undef NDEBUG
#define DEBUG 1
#include <assert.h>
#include <stdio.h>
#include <string.h>

#define pf printf
#define ps puts
/* Very common printf() args combo. */
#define zNM zName, zMode

/*
** Valid names for the zName arguments.
*/
#define JS_BUILD_NAMES sqlite3 sqlite3-wasmfs
/*
** Valid names for the zMode arguments of the "sqlite3" build. For the
** "sqlite3-wasmfs" build, only "esm" (ES6 Module) is legal.
*/
#define JS_BUILD_MODES vanilla esm bundler-friendly node
static const char * zBanner =
  "\n########################################################################\n";

/*
** Emits common vars needed by the rest of the emitted code (but not
** needed by makefile code outside of these generated pieces).
*/
static void mk_prologue(void){
  pf("%s", zBanner);
  ps("# extern-post-js* and extern-pre-js* are files for use with");
  ps("# Emscripten's --extern-pre-js and --extern-post-js flags.");
  ps("extern-pre-js.js := $(dir.api)/extern-pre-js.js");
  ps("extern-post-js.js.in := $(dir.api)/extern-post-js.c-pp.js");
  ps("# Emscripten flags for --[extern-][pre|post]-js=... for the");
  ps("# various builds.");
  ps("pre-post-common.flags := --extern-pre-js=$(sqlite3-license-version.js)");
  ps("# pre-post-jses.deps.* = a list of dependencies for the");
  ps("# --[extern-][pre/post]-js files.");
  ps("pre-post-jses.deps.common := $(extern-pre-js.js) $(sqlite3-license-version.js)");
}

/*
** Emits makefile code for setting up values for the --pre-js=FILE,
** --post-js=FILE, and --extern-post-js=FILE emcc flags, as well as
** populating those files.
*/
static void mk_pre_post(const char *zName  /* build name */,
                        const char *zMode  /* build mode */,
                        const char *zCmppD /* optional -D flags for c-pp for the
                                           ** --pre/--post-js files. */){
  pf("%s# Begin --pre/--post flags for %s-%s\n", zBanner, zNM);
  pf("c-pp.D.%s-%s := %s\n", zNM, zCmppD ? zCmppD : "");
  pf("pre-post-%s-%s.flags ?=\n", zNM);

  /* --pre-js=... */
  pf("pre-js.js.%s-%s := $(dir.tmp)/pre-js.%s-%s.js\n",
     zNM, zNM);
  pf("$(pre-js.js.%s-%s): $(MAKEFILE)\n", zNM);
#if 1
  pf("$(eval $(call C-PP.FILTER,$(pre-js.js.in),$(pre-js.js.%s-%s),"
     "$(c-pp.D.%s-%s)))\n", zNM, zNM);
#else
  /* This part is needed if/when we re-enable the custom
  ** Module.instantiateModule() impl in api/pre-js.c-pp.js. */
  pf("pre-js.js.%s-%s.intermediary := $(dir.tmp)/pre-js.%s-%s.intermediary.js\n",
     zNM, zNM);
  pf("$(eval $(call C-PP.FILTER,$(pre-js.js.in),$(pre-js.js.%s-%s.intermediary),"
     "$(c-pp.D.%s-%s) -Dcustom-Module.instantiateModule))\n", zNM, zNM);
  pf("$(pre-js.js.%s-%s): $(pre-js.js.%s-%s.intermediary)\n", zNM, zNM);
  pf("\tcp $(pre-js.js.%s-%s.intermediary) $@\n", zNM);

  /* Amend $(pre-js.js.zName-zMode) for all targets except the plain
  ** "sqlite3" build... */
  if( 0!=strcmp("sqlite3-wasmfs", zName)
      && 0!=strcmp("sqlite3", zName) ){
    pf("\t@echo 'Module[xNameOfInstantiateWasm].uri = "
       "\"%s.wasm\";' >> $@\n", zName);
  }
#endif

  /* --post-js=... */
  pf("post-js.js.%s-%s := $(dir.tmp)/post-js.%s-%s.js\n", zNM, zNM);
  pf("$(eval $(call C-PP.FILTER,$(post-js.js.in),"
     "$(post-js.js.%s-%s),$(c-pp.D.%s-%s)))\n", zNM, zNM);

  /* --extern-post-js=... */
  pf("extern-post-js.js.%s-%s := $(dir.tmp)/extern-post-js.%s-%s.js\n", zNM, zNM);
  pf("$(eval $(call C-PP.FILTER,$(extern-post-js.js.in),$(extern-post-js.js.%s-%s),"
     "$(c-pp.D.%s-%s)))\n", zNM, zNM);

  /* Combine flags for use with emcc... */
  pf("pre-post-common.flags.%s-%s := "
     "$(pre-post-common.flags) "
     "--post-js=$(post-js.js.%s-%s) "
     "--extern-post-js=$(extern-post-js.js.%s-%s)\n", zNM, zNM, zNM);

  pf("pre-post-%s-%s.flags += $(pre-post-common.flags.%s-%s) "
     "--pre-js=$(pre-js.js.%s-%s)\n", zNM, zNM, zNM);

  /* Set up deps... */
  pf("pre-post-jses.%s-%s.deps := $(pre-post-jses.deps.common) "
     "$(post-js.js.%s-%s) $(extern-post-js.js.%s-%s)\n",
     zNM, zNM, zNM);
  pf("pre-post-%s-%s.deps := $(pre-post-jses.%s-%s.deps) $(dir.tmp)/pre-js.%s-%s.js\n",
     zNM, zNM, zNM);
  pf("# End --pre/--post flags for %s-%s%s", zNM, zBanner);
}

/*
** Emits rules for the fiddle builds.
**
*/
static void mk_fiddle(){
  int i = 0;

  mk_pre_post("fiddle-module","vanilla", 0);
  for( ; i < 2; ++i ){
    const char *zTail = i ? ".debug" : "";
    const char *zDir = i ? "$(dir.fiddle-debug)" : "$(dir.fiddle)";

    pf("%s# Begin fiddle%s\n", zBanner, zTail);
    pf("fiddle-module.js%s := %s/fiddle-module.js\n", zTail, zDir);
    pf("fiddle-module.wasm%s := "
       "$(subst .js,.wasm,$(fiddle-module.js%s))\n", zTail, zTail);
    pf("$(fiddle-module.js%s):%s $(MAKEFILE) $(MAKEFILE.fiddle) "
       "$(EXPORTED_FUNCTIONS.fiddle) "
       "$(fiddle.cses) $(pre-post-fiddle-module-vanilla.deps) "
       "$(SOAP.js)\n",
       zTail, (i ? " $(fiddle-module.js)" : ""));
    if( 1==i ){/*fiddle.debug*/
      pf("	@test -d \"$(dir $@)\" || mkdir -p \"$(dir $@)\"\n");
    }
    pf("	$(emcc.bin) -o $@ $(fiddle.emcc-flags%s) "
       "$(pre-post-fiddle-module-vanilla.flags) $(fiddle.cses)\n",
       zTail);
    pf("	$(maybe-wasm-strip) $(fiddle-module.wasm%s)\n", zTail);
    pf("	@cp -p $(SOAP.js) $(dir $@)\n");
    if( 1==i ){/*fiddle.debug*/
      pf("	cp -p $(dir.fiddle)/index.html "
         "$(dir.fiddle)/fiddle.js "
         "$(dir.fiddle)/fiddle-worker.js "
         "$(dir $@)\n");
    }
    pf("	@for i in %s/*.*js %s/*.html %s/*.wasm; do \\\n"
       "		test -f $${i} || continue;             \\\n"
       "		gzip < $${i} > $${i}.gz; \\\n"
       "	done\n", zDir, zDir, zDir);
    if( 0==i ){
      ps("fiddle: $(fiddle-module.js)");
    }else{
      ps("fiddle-debug: $(fiddle-module-debug.js)");
    }
    pf("# End fiddle%s%s", zTail, zBanner);
  }
}

/*
** Emits makefile code for one build of the library, primarily defined
** by the combination of zName and zMode, each of which must be values
** from JS_BUILD_NAMES resp. JS_BUILD_MODES.
*/
static void mk_lib_mode(const char *zName     /* build name */,
                        const char *zMode     /* build mode */,
                        int bIsEsm            /* true only for ESM build */,
                        const char *zApiJsOut /* name of generated sqlite3-api.js/.mjs */,
                        const char *zJsOut    /* name of generated sqlite3.js/.mjs */,
                        const char *zCmppD    /* extra -D flags for c-pp */,
                        const char *zEmcc     /* extra flags for emcc */){
  assert( zName );
  assert( zMode );
  assert( zApiJsOut );
  assert( zJsOut );
  if( !zCmppD ) zCmppD = "";
  if( !zEmcc ) zEmcc = "";

  pf("%s# Begin build [%s-%s]\n", zBanner, zNM);
  pf("ifneq (1,$(MAKING_CLEAN))\n");
  pf("$(info Setting up build [%s-%s]: %s)\n", zNM, zJsOut);
  mk_pre_post(zNM, zCmppD);
  pf("\nemcc.flags.%s.%s ?=\n", zNM);
  if( zEmcc[0] ){
    pf("emcc.flags.%s.%s += %s\n", zNM, zEmcc);
  }
  pf("$(eval $(call C-PP.FILTER, $(sqlite3-api.js.in), %s, %s))\n",
     zApiJsOut, zCmppD);

  /* target zJsOut */
  pf("%s: %s $(MAKEFILE) $(sqlite3-wasm.cfiles) $(EXPORTED_FUNCTIONS.api) "
     "$(pre-post-%s-%s.deps)\n",
     zJsOut, zApiJsOut, zNM);
  pf("\t@echo \"Building $@ ...\"\n");
  pf("\t$(emcc.bin) -o $@ $(emcc_opt_full) $(emcc.flags) \\\n");
  pf("\t\t$(emcc.jsflags) -sENVIRONMENT=$(emcc.environment.%s) \\\n", zMode);
  pf("\t\t$(pre-post-%s-%s.flags) \\\n", zNM);
  pf("\t\t$(emcc.flags.%s) $(emcc.flags.%s.%s) \\\n", zName, zNM);
  pf("\t\t$(cflags.common) $(SQLITE_OPT) \\\n"
     "\t\t$(cflags.%s) $(cflags.%s.%s) \\\n"
     "\t\t$(cflags.wasm_extra_init) $(sqlite3-wasm.cfiles)\n", zName, zNM);
  if( bIsEsm ){
    /* TODO? Replace this CALL with the corresponding makefile code.
    ** OTOH, we also use this $(call) in the speedtest1-wasmfs build,
    ** which is not part of the rules emitted by this program. */
    pf("\t@$(call SQLITE3.xJS.ESM-EXPORT-DEFAULT,1,%d)\n",
       0==strcmp("sqlite3-wasmfs", zName) ? 1 : 0);
  }
  pf("\t@dotwasm=$(basename $@).wasm; \\\n"
     "\tchmod -x $$dotwasm; \\\n"
     "\t$(maybe-wasm-strip) $$dotwasm; \\\n");
  pf("\tsed -i -e '/^var _sqlite3.*createExportWrapper/d' %s; \\\n"
     "\techo 'Stripped out createExportWrapper() parts.'; \\\n",
     zJsOut) /* Our JS code installs bindings of each WASM export. The
                generated Emscripten JS file does the same using its
                own framework, but we don't use those results and can
                speed up lib init, and reduce memory cost
                considerably, by stripping them out. */;
  /*
  ** The above $(emcc.bin) call will write zJsOut and will create a
  ** like-named .wasm file. That .wasm file name gets hard-coded into
  ** zJsOut so we need to, for some cases, patch zJsOut to use the
  ** name sqlite3.wasm instead. Note that the resulting .wasm file is
  ** identical for all builds for which zEmcc is empty.
  */
  if( 0==strcmp("bundler-friendly", zMode)
      || 0==strcmp("node", zMode) ) {
    pf("\techo 'Patching $@ for %s.wasm...' \\\n", zName);
    pf("\trm -f $$dotwasm; dotwasm=; \\\n"
       "\tsed -i -e 's/%s-%s.wasm/%s.wasm/g' $@ || exit $$?; \\\n",
       zNM, zName);
  }
  pf("\tls -la $$dotwasm $@\n");
  if( 0!=strcmp("sqlite3-wasmfs", zName) ){
    /* The sqlite3-wasmfs build is optional and needs to be invoked
    ** conditionally using info we don't have here. */
    pf("all: %s\n", zJsOut);
  }
  ps("endif\n# ^^^ !$(MAKING_CLEAN)");
  pf("# End build [%s-%s]%s", zNM, zBanner);
}

int main(void){
  int rc = 0;
  pf("# What follows was GENERATED by %s. Edit at your own risk.\n", __FILE__);
  mk_prologue();
  mk_lib_mode("sqlite3", "vanilla", 0,
              "$(sqlite3-api.js)", "$(sqlite3.js)", 0, 0);
  mk_lib_mode("sqlite3", "esm", 1,
              "$(sqlite3-api.mjs)", "$(sqlite3.mjs)",
              "-Dtarget=es6-module", 0);
  mk_lib_mode("sqlite3", "bundler-friendly", 1,
              "$(sqlite3-api-bundler-friendly.mjs)", "$(sqlite3-bundler-friendly.mjs)",
              "$(c-pp.D.sqlite3-esm) -Dtarget=es6-bundler-friendly", 0);
  mk_lib_mode("sqlite3" , "node", 1,
              "$(sqlite3-api-node.mjs)", "$(sqlite3-node.mjs)",
              "$(c-pp.D.sqlite3-bundler-friendly) -Dtarget=node", 0);
  mk_lib_mode("sqlite3-wasmfs", "esm" ,1,
              "$(sqlite3-api-wasmfs.mjs)", "$(sqlite3-wasmfs.mjs)",
              "$(c-pp.D.sqlite3-bundler-friendly) -Dwasmfs",
              "-sEXPORT_ES6 -sUSE_ES6_IMPORT_META");

  mk_fiddle();
  mk_pre_post("speedtest1","vanilla", 0);
  mk_pre_post("speedtest1-wasmfs","esm", "$(c-pp.D.sqlite3-bundler-friendly) -Dwasmfs");
  return rc;
}