To search for included modules, and track dependencies between them.

§1. Creation. Each web of source material discovered by Inweb is given one of the following. Ordinarily these are found only when reading in a web for weaving, tangling and so on: in the vast majority of Inweb runs, all modules will have the "module origin marker" READING_WEB_MOM. But when Inweb is constructing a makefile for a suite of tools, it can also discover multiple webs by other means. 

enum READING_WEB_MOM from 0
enum MAKEFILE_TOOL_MOM
enum MAKEFILE_WEB_MOM
enum MAKEFILE_MODULE_MOM

typedef struct module {
    struct pathname *module_location;
    struct text_stream *module_name;
    struct linked_list *dependencies;  of module: which other modules does this need?
    struct text_stream *module_tag;
    int origin_marker;  one of the *_MOM values above
    struct linked_list *chapters_md;  of chapter_md: just the ones in this module
    struct linked_list *sections_md;  of section_md: just the ones in this module
    CLASS_DEFINITION
} module;

§2. 

module *WebModules::new(text_stream *name, pathname *at, int m) {
    module *M = CREATE(module);
    M->module_location = at;
    M->module_name = Str::duplicate(name);
    M->dependencies = NEW_LINKED_LIST(module);
    M->origin_marker = m;
    M->module_tag = I"miscellaneous";
    M->chapters_md = NEW_LINKED_LIST(chapter_md);
    M->sections_md = NEW_LINKED_LIST(section_md);
    return M;
}

§3. In the Inweb documentation, "module" is used to refer to a sidekick web which contains a suite of utility routines, or a major component of a program, but which is not a program in its own right.

Internally, though, every web produces a module structure. The one for the main web — which can be tangled, and results in an actual program — is internally named "(main)", a name which the user will never see. 

module *WebModules::create_main_module(web_md *WS) {
    return WebModules::new(I"(main)", WS->path_to_web, READING_WEB_MOM);
}

§4. Dependencies. When web A imports module B, we will say that A is dependent on B. A web can import multiple modules, so there can a list of dependencies. These are needed when constructing makefiles, since the source code in B affects the program generated by A. 

void WebModules::dependency(module *A, module *B) {
    if ((A == NULL) || (B == NULL)) internal_error("no module");
    ADD_TO_LINKED_LIST(B, module, A->dependencies);
}

§5. Searching. The following abstracts the idea of a place where modules might be found. (At one time there was going to be a more elaborate search hierarchy.) 

typedef struct module_search {
    struct pathname *path_to_search;
    CLASS_DEFINITION
} module_search;

§6. 

module_search *WebModules::make_search_path(pathname *ext_path) {
    module_search *ms = CREATE(module_search);
    ms->path_to_search = ext_path;
    return ms;
}

§7. When a web's contents page says to import Blah, how do we find the module called Blah on disc? We try four possibilities in sequence: 

module *WebModules::find(web_md *WS, module_search *ms, text_stream *name, pathname *X) {
    TEMPORARY_TEXT(T)
    WRITE_TO(T, "%S-module", name);
    pathname *tries[4];
    tries[0] = WS?(WS->path_to_web):NULL;
    tries[1] = tries[0]?(Pathnames::up(tries[0])):NULL;
    tries[2] = X;
    tries[3] = ms->path_to_search;
    int N = 4;
    for (int i=0; i<N; i++) {
        pathname *P = Pathnames::from_text_relative(tries[i], T);
        if ((P) && (WebModules::exists(P))) Accept this directory as the module7.1;
    }
    DISCARD_TEXT(T)
    return NULL;
}

§7.1. When the module is found (if it is), a suitable module structure is made, and a dependency created from the web's (main) module to this one.

Accept this directory as the module7.1 = 

    pathname *Q = Pathnames::from_text(name);
    module *M = WebModules::new(Pathnames::directory_name(Q), P, READING_WEB_MOM);
    WebModules::dependency(WS->as_module, M);
    return M;

§8. We accept that a plausibly-named directory is indeed the module being sought if it looks like a web. 

int WebModules::exists(pathname *P) {
    return WebMetadata::directory_looks_like_a_web(P);
}

§9. Resolving cross-reference names. Suppose we are in module from_M and want to understand which section of a relevant web text might refer to. It could be the name of a module, either this one or one dependent on it; or the name of a chapter in one of those, or the shortened forms of those; or the name of a section. It may match multiple possibilities: we return how many, and if this is positive, we write the module in which the first find was made in *return M, the section in *return_Sm, and set the flag *named_as_module according to whether the reference was a bare module name (say, "foundation") or not.

Note that we consider first the possibilities within from_M: we only look at other modules if there are none. Thus, an unambiguous result in from_M is good enough, even if there are other possibilities elsewhere.

A reference in the form module: reference is taken to be in the module of that name: for example, "foundation: Web Modules" would find the section of code you are now reading. 

int WebModules::named_reference(module **return_M, section_md **return_Sm,
    int *named_as_module, text_stream *title, module *from_M, text_stream *text,
    int list, int sections_only) {
    *return_M = NULL; *return_Sm = NULL; *named_as_module = FALSE;
    module *M;
    int finds = 0;
    if (from_M == NULL) return 0;
    match_results mr = Regexp::create_mr();
    text_stream *seek = text;
    text_stream *seek_module = NULL;
    if (Regexp::match(&mr, text, U"(%C+?): *(%c+?) *")) {
        seek_module = mr.exp[0]; seek = mr.exp[1];
    } else {
        seek_module = from_M->module_name; seek = text;
    }
    LOOP_OVER_LINKED_LIST(M, module, from_M->dependencies) {
        if (Str::eq_insensitive(M->module_name, seek_module)) {
            Look for references to chapters or sections in M9.1;
        }
    }
    Regexp::dispose_of(&mr);
    seek = text;
    for (int stage = 1; ((finds == 0) && (stage <= 2)); stage++) {
        if (stage == 1) {
            M = from_M;
            Look for references to chapters or sections in M9.1;
        }
        if (stage == 2) {
            LOOP_OVER_LINKED_LIST(M, module, from_M->dependencies)
                Look for references to chapters or sections in M9.1;
        }
    }
    return finds;
}

§9.1. Look for references to chapters or sections in M9.1 = 

    if (M == NULL) internal_error("no module");
    if (Str::eq_insensitive(M->module_name, seek))
        Found first section in module9.1.1;
    chapter_md *Cm;
    section_md *Sm;
    LOOP_OVER_LINKED_LIST(Cm, chapter_md, M->chapters_md) {
        if ((sections_only == FALSE) &&
            ((Str::eq_insensitive(Cm->ch_title, seek)) ||
            (Str::eq_insensitive(Cm->ch_basic_title, seek)) ||
            (Str::eq_insensitive(Cm->ch_decorated_title, seek))))
            Found first section in chapter9.1.2;
        LOOP_OVER_LINKED_LIST(Sm, section_md, Cm->sections_md)
            if (Str::eq_insensitive(Sm->sect_title, seek))
                Found section by name9.1.3;
    }

§9.1.1. Found first section in module9.1.1 = 

    finds++;
    if (finds == 1) {
        *return_M = M; *return_Sm = FIRST_IN_LINKED_LIST(section_md, M->sections_md);
        *named_as_module = TRUE;
        WRITE_TO(title, "the %S module", M->module_name);
    }
    if (list) WRITE_TO(STDERR, "(%d)  Module '%S'\n", finds, M->module_name);

§9.1.2. Found first section in chapter9.1.2 = 

    finds++;
    if (finds == 1) {
        *return_M = M; *return_Sm = FIRST_IN_LINKED_LIST(section_md, Cm->sections_md);
        WRITE_TO(title, "%S", Cm->ch_title);
    }
    if (list) WRITE_TO(STDERR, "(%d)  Chapter '%S' of module '%S'\n",
        finds, Cm->ch_title, M->module_name);

§9.1.3. Found section by name9.1.3 = 

    finds++;
    if (finds == 1) {
        *return_M = M; *return_Sm = Sm;
        WRITE_TO(title, "%S", Sm->sect_title);
    }
    if (list) WRITE_TO(STDERR, "(%d)  Section '%S' in chapter '%S' of module '%S'\n",
        finds, Sm->sect_title, Cm->ch_title, M->module_name);