#include "fstate.hh"
#include "globals.hh"
#include "store.hh"


string printTerm(ATerm t)
{
    char * s = ATwriteToString(t);
    return s;
}


Error badTerm(const format & f, ATerm t)
{
    return Error(format("%1%, in `%2%'") % f.str() % printTerm(t));
}


Hash hashTerm(ATerm t)
{
    return hashString(printTerm(t));
}


ATerm termFromId(const FSId & id)
{
    string path = expandId(id);
    ATerm t = ATreadFromNamedFile(path.c_str());
    if (!t) throw Error(format("cannot read aterm from `%1%'") % path);
    return t;
}


FSId writeTerm(ATerm t, const string & suffix)
{
    FSId id = hashTerm(t);

    string path = canonPath(nixStore + "/" + 
        (string) id + suffix + ".nix");
    if (!ATwriteToNamedTextFile(t, path.c_str()))
        throw Error(format("cannot write aterm %1%") % path);

//     debug(format("written term %1% = %2%") % (string) id %
//         printTerm(t));

    registerPath(path, id);
    return id;
}


static void parseIds(ATermList ids, FSIds & out)
{
    while (!ATisEmpty(ids)) {
        char * s;
        ATerm id = ATgetFirst(ids);
        if (!ATmatch(id, "<str>", &s))
            throw badTerm("not an id", id);
        out.push_back(parseHash(s));
        ids = ATgetNext(ids);
    }
}


typedef set<FSId> FSIdSet;


static void checkSlice(const Slice & slice)
{
    if (slice.elems.size() == 0)
        throw Error("empty slice");

    FSIdSet decl;
    for (SliceElems::const_iterator i = slice.elems.begin();
         i != slice.elems.end(); i++)
        decl.insert(i->id);
    
    for (FSIds::const_iterator i = slice.roots.begin();
         i != slice.roots.end(); i++)
        if (decl.find(*i) == decl.end())
            throw Error(format("undefined id: %1%") % (string) *i);
    
    for (SliceElems::const_iterator i = slice.elems.begin();
         i != slice.elems.end(); i++)
        for (FSIds::const_iterator j = i->refs.begin();
             j != i->refs.end(); j++)
            if (decl.find(*j) == decl.end())
                throw Error(format("undefined id: %1%") % (string) *j);
}


/* Parse a slice. */
static bool parseSlice(ATerm t, Slice & slice)
{
    ATermList roots, elems;
    
    if (!ATmatch(t, "Slice([<list>], [<list>])", &roots, &elems))
        return false;

    parseIds(roots, slice.roots);

    while (!ATisEmpty(elems)) {
        char * s1, * s2;
        ATermList refs;
        ATerm t = ATgetFirst(elems);
        if (!ATmatch(t, "(<str>, <str>, [<list>])", &s1, &s2, &refs))
            throw badTerm("not a slice element", t);
        SliceElem elem;
        elem.path = s1;
        elem.id = parseHash(s2);
        parseIds(refs, elem.refs);
        slice.elems.push_back(elem);
        elems = ATgetNext(elems);
    }

    checkSlice(slice);
    return true;
}


static bool parseDerive(ATerm t, Derive & derive)
{
    ATermList outs, ins, bnds;
    char * builder;
    char * platform;

    if (!ATmatch(t, "Derive([<list>], [<list>], <str>, <str>, [<list>])",
            &outs, &ins, &builder, &platform, &bnds))
        return false;

    while (!ATisEmpty(outs)) {
        char * s1, * s2;
        ATerm t = ATgetFirst(outs);
        if (!ATmatch(t, "(<str>, <str>)", &s1, &s2))
            throw badTerm("not a derive output", t);
        derive.outputs.push_back(DeriveOutput(s1, parseHash(s2)));
        outs = ATgetNext(outs);
    }

    parseIds(ins, derive.inputs);

    derive.builder = builder;
    derive.platform = platform;
    
    while (!ATisEmpty(bnds)) {
        char * s1, * s2;
        ATerm bnd = ATgetFirst(bnds);
        if (!ATmatch(bnd, "(<str>, <str>)", &s1, &s2))
            throw badTerm("tuple of strings expected", bnd);
        derive.env.push_back(StringPair(s1, s2));
        bnds = ATgetNext(bnds);
    }

    return true;
}


FState parseFState(ATerm t)
{
    FState fs;
    if (parseSlice(t, fs.slice))
        fs.type = FState::fsSlice;
    else if (parseDerive(t, fs.derive))
        fs.type = FState::fsDerive;
    else throw badTerm("not an fstate-expression", t);
    return fs;
}


static ATermList unparseIds(const FSIds & ids)
{
    ATermList l = ATempty;
    for (FSIds::const_iterator i = ids.begin();
         i != ids.end(); i++)
        l = ATinsert(l,
            ATmake("<str>", ((string) *i).c_str()));
    return ATreverse(l);
}


static ATerm unparseSlice(const Slice & slice)
{
    ATermList roots = unparseIds(slice.roots);
    
    ATermList elems = ATempty;
    for (SliceElems::const_iterator i = slice.elems.begin();
         i != slice.elems.end(); i++)
        elems = ATinsert(elems,
            ATmake("(<str>, <str>, <term>)",
                i->path.c_str(),
                ((string) i->id).c_str(),
                unparseIds(i->refs)));

    return ATmake("Slice(<term>, <term>)", roots, elems);
}


static ATerm unparseDerive(const Derive & derive)
{
    ATermList outs = ATempty;
    for (DeriveOutputs::const_iterator i = derive.outputs.begin();
         i != derive.outputs.end(); i++)
        outs = ATinsert(outs,
            ATmake("(<str>, <str>)", 
                i->first.c_str(), ((string) i->second).c_str()));
    
    ATermList env = ATempty;
    for (StringPairs::const_iterator i = derive.env.begin();
         i != derive.env.end(); i++)
        env = ATinsert(env,
            ATmake("(<str>, <str>)", 
                i->first.c_str(), i->second.c_str()));

    return ATmake("Derive(<term>, <term>, <str>, <str>, <term>)",
        ATreverse(outs),
        unparseIds(derive.inputs),
        derive.builder.c_str(),
        derive.platform.c_str(),
        ATreverse(env));
}


ATerm unparseFState(const FState & fs)
{
    if (fs.type == FState::fsSlice)
        return unparseSlice(fs.slice);
    else if (fs.type == FState::fsDerive)
        return unparseDerive(fs.derive);
    else abort();
}