#include "globals.hh"
#include "normalise.hh"
#include "shared.hh"
#include "parser.hh"
#include "eval.hh"
#include "help.txt.hh"


typedef void (* Operation) (EvalState & state,
    Strings opFlags, Strings opArgs);


struct DrvInfo
{
    string name;
    Path drvPath;
    Path outPath;
    Hash drvHash;
};

typedef map<Path, DrvInfo> DrvInfos;


void printHelp()
{
    cout << string((char *) helpText, sizeof helpText);
}


bool parseDerivation(EvalState & state, Expr e, DrvInfo & drv)
{
    ATMatcher m;
    
    e = evalExpr(state, e);
    if (!(atMatch(m, e) >> "Attrs")) return false;
    Expr a = queryAttr(e, "type");
    if (!a || evalString(state, a) != "derivation") return false;

    a = queryAttr(e, "name");
    if (!a) throw badTerm("derivation name missing", e);
    drv.name = evalString(state, a);

    a = queryAttr(e, "drvPath");
    if (!a) throw badTerm("derivation path missing", e);
    drv.drvPath = evalPath(state, a);

    a = queryAttr(e, "drvHash");
    if (!a) throw badTerm("derivation hash missing", e);
    drv.drvHash = parseHash(evalString(state, a));

    a = queryAttr(e, "outPath");
    if (!a) throw badTerm("output path missing", e);
    drv.outPath = evalPath(state, a);

    return true;
}


bool parseDerivations(EvalState & state, Expr e, DrvInfos & drvs)
{
    ATMatcher m;
    ATermList es;
    DrvInfo drv;

    e = evalExpr(state, e);

    if (parseDerivation(state, e, drv)) 
        drvs[drv.drvPath] = drv;

    else if (atMatch(m, e) >> "Attrs") {
        ATermMap drvMap;
        queryAllAttrs(e, drvMap);
        for (ATermIterator i(drvMap.keys()); i; ++i) {
            debug(format("evaluating attribute `%1%'") % *i);
            if (parseDerivation(state, drvMap.get(*i), drv))
                drvs[drv.drvPath] = drv;
        }
    }

    else if (atMatch(m, e) >> "List" >> es) {
        for (ATermIterator i(es); i; ++i) {
            debug(format("evaluating list element"));
            if (parseDerivation(state, *i, drv))
                drvs[drv.drvPath] = drv;
        }
    }

    return true;
}


void loadDerivations(EvalState & state, Path nePath, DrvInfos & drvs)
{
    Expr e = parseExprFromFile(absPath(nePath));
    if (!parseDerivations(state, e, drvs))
        throw badTerm("expected set of derivations", e);
}


static Path getLinksDir()
{
    return canonPath(nixStateDir + "/links");
}


static Path getCurrentPath()
{
    return getLinksDir() + "/current";
}


void queryInstalled(EvalState & state, DrvInfos & drvs)
{
    Path path = getCurrentPath() + "/manifest";

    if (!pathExists(path)) return; /* not an error, assume nothing installed */

    Expr e = ATreadFromNamedFile(path.c_str());
    if (!e) throw Error(format("cannot read Nix expression from `%1%'") % path);

    if (!parseDerivations(state, e, drvs))
        throw badTerm(format("expected set of derivations in `%1%'") % path, e);
}


Path createLink(Path outPath, Path drvPath)
{
    Path linksDir = getLinksDir();

    unsigned int num = 0;
    
    Strings names = readDirectory(linksDir);
    for (Strings::iterator i = names.begin(); i != names.end(); ++i) {
        istringstream s(*i);
        unsigned int n; 
        if (s >> n && s.eof() && n >= num) num = n + 1;
    }

    Path linkPath;

    while (1) {
        linkPath = (format("%1%/%2%") % linksDir % num).str();
        if (symlink(outPath.c_str(), linkPath.c_str()) == 0) break;
        if (errno != EEXIST)
            throw SysError(format("creating symlink `%1%'") % linkPath);
        /* Somebody beat us to it, retry with a higher number. */
        num++;
    }

    writeStringToFile(linkPath + "-src.id", drvPath);

    return linkPath;
}


void switchLink(Path link, Path target)
{
    Path tmp = canonPath(dirOf(link) + "/.new_" + baseNameOf(link));
    if (symlink(target.c_str(), tmp.c_str()) != 0)
        throw SysError(format("creating symlink `%1%'") % tmp);
    /* The rename() system call is supposed to be essentially atomic
       on Unix.  That is, if we have links `current -> X' and
       `new_current -> Y', and we rename new_current to current, a
       process accessing current will see X or Y, but never a
       file-not-found or other error condition.  This is sufficient to
       atomically switch user environments. */
    if (rename(tmp.c_str(), link.c_str()) != 0)
        throw SysError(format("renaming `%1%' to `%2%'") % tmp % link);
}


void createUserEnv(EvalState & state, const DrvInfos & drvs)
{
    /* Get the environment builder expression. */
    Expr envBuilder = parseExprFromFile(nixDataDir + "/nix/corepkgs/buildenv"); /* !!! */

    /* Construct the whole top level derivation. */
    ATermList inputs = ATempty;
    for (DrvInfos::const_iterator i = drvs.begin(); 
         i != drvs.end(); ++i)
    {
        ATerm t = ATmake(
            "Attrs(["
            "Bind(\"type\", Str(\"derivation\")), "
            "Bind(\"name\", Str(<str>)), "
            "Bind(\"drvPath\", Path(<str>)), "
            "Bind(\"drvHash\", Str(<str>)), "
            "Bind(\"outPath\", Path(<str>))"
            "])",
            i->second.name.c_str(),
            i->second.drvPath.c_str(),
            ((string) i->second.drvHash).c_str(),
            i->second.outPath.c_str());
        inputs = ATinsert(inputs, t);
    }

    ATerm inputs2 = ATmake("List(<term>)", ATreverse(inputs));

    /* Also write a copy of the list of inputs to the store; we need
       it for future modifications of the environment. */
    Path inputsFile = writeTerm(inputs2, "-env-inputs");

    Expr topLevel = ATmake(
        "Call(<term>, Attrs(["
        "Bind(\"system\", Str(<str>)), "
        "Bind(\"derivations\", <term>), " // !!! redundant
        "Bind(\"manifest\", Path(<str>))"
        "]))",
        envBuilder, thisSystem.c_str(), inputs2, inputsFile.c_str());

    /* Instantiate it. */
    debug(format("evaluating builder expression `%1%'") % topLevel);
    DrvInfo topLevelDrv;
    if (!parseDerivation(state, topLevel, topLevelDrv))
        abort();
    
    /* Realise the resulting store expression. */
    debug(format("realising user environment"));
    Path nfPath = normaliseStoreExpr(topLevelDrv.drvPath);
    realiseClosure(nfPath);

    /* Switch the current user environment to the output path. */
    debug(format("switching to new user environment"));
    Path linkPath = createLink(topLevelDrv.outPath, topLevelDrv.drvPath);
    switchLink(getLinksDir() + "/current", linkPath);
}


typedef map<string, Path> NameMap;


NameMap mapByNames(DrvInfos & drvs)
{
    NameMap nameMap;
    for (DrvInfos::iterator i = drvs.begin(); i != drvs.end(); ++i)
        nameMap[i->second.name] = i->first;
    return nameMap;
}


void installDerivations(EvalState & state,
    Path nePath, Strings drvNames)
{
    debug(format("installing derivations from `%1%'") % nePath);

    /* Fetch all derivations from the input file. */
    DrvInfos availDrvs;
    loadDerivations(state, nePath, availDrvs);

    NameMap nameMap = mapByNames(availDrvs);

    /* Filter out the ones we're not interested in. */
    DrvInfos selectedDrvs;
    if (drvNames.size() > 0 && drvNames.front() == "*") { /* !!! hack */
        selectedDrvs = availDrvs;
    } else {
        for (Strings::iterator i = drvNames.begin();
             i != drvNames.end(); ++i)
        {
            NameMap::iterator j = nameMap.find(*i);
            if (j == nameMap.end())
                throw Error(format("unknown derivation `%1%'") % *i);
            else
                selectedDrvs[j->second] = availDrvs[j->second];
        }
    }

    /* Add in the already installed derivations. */
    DrvInfos installedDrvs;
    queryInstalled(state, installedDrvs);
    selectedDrvs.insert(installedDrvs.begin(), installedDrvs.end());

    createUserEnv(state, selectedDrvs);
}


static void opInstall(EvalState & state,
    Strings opFlags, Strings opArgs)
{
    if (opArgs.size() < 1) throw UsageError("Nix file expected");

    Path nePath = opArgs.front();
    opArgs.pop_front();

    installDerivations(state, nePath,
        Strings(opArgs.begin(), opArgs.end()));
}


void uninstallDerivations(EvalState & state, Strings drvNames)
{
    DrvInfos installedDrvs;
    queryInstalled(state, installedDrvs);

    NameMap nameMap = mapByNames(installedDrvs);

    for (Strings::iterator i = drvNames.begin();
         i != drvNames.end(); ++i)
    {
        NameMap::iterator j = nameMap.find(*i);
        if (j == nameMap.end())
            throw Error(format("unknown derivation `%1%'") % *i);
        else
            installedDrvs.erase(j->second);
    }

    createUserEnv(state, installedDrvs);
}


static void opUninstall(EvalState & state,
    Strings opFlags, Strings opArgs)
{
    uninstallDerivations(state, opArgs);
}


static void opQuery(EvalState & state,
    Strings opFlags, Strings opArgs)
{
    enum { qName, qDrvPath, qStatus } query = qName;
    enum { sInstalled, sAvailable } source = sInstalled;

    for (Strings::iterator i = opFlags.begin();
         i != opFlags.end(); ++i)
        if (*i == "--name") query = qName;
        else if (*i == "--expr" || *i == "-e") query = qDrvPath;
        else if (*i == "--status" || *i == "-s") query = qStatus;
        else if (*i == "--installed") source = sInstalled;
        else if (*i == "--available" || *i == "-f") source = sAvailable;
        else throw UsageError(format("unknown flag `%1%'") % *i);

    /* Obtain derivation information from the specified source. */
    DrvInfos drvs;

    switch (source) {

        case sInstalled:
            queryInstalled(state, drvs);
            break;

        case sAvailable: {
            if (opArgs.size() < 1) throw UsageError("Nix file expected");
            Path nePath = opArgs.front();
            opArgs.pop_front();
            loadDerivations(state, nePath, drvs);
            break;
        }

        default: abort();
    }

    if (opArgs.size() != 0) throw UsageError("no arguments expected");
    
    /* Perform the specified query on the derivations. */
    switch (query) {

        case qName: {
            for (DrvInfos::iterator i = drvs.begin(); i != drvs.end(); ++i)
                cout << format("%1%\n") % i->second.name;
            break;
        }
        
        case qDrvPath: {
            for (DrvInfos::iterator i = drvs.begin(); i != drvs.end(); ++i)
                cout << format("%1%\n") % i->second.drvPath;
            break;
        }
        
        case qStatus: {
            DrvInfos installed;
            queryInstalled(state, installed);

            for (DrvInfos::iterator i = drvs.begin(); i != drvs.end(); ++i) {
                cout << format("%1%%2% %3%\n")
                    % (installed.find(i->first) != installed.end() ? 'I' : '-')
                    % (isValidPath(i->second.outPath) ? 'P' : '-')
                    % i->second.name;
            }
            break;
        }
        
        default: abort();
    }
}


void run(Strings args)
{
    EvalState state;
    Strings opFlags, opArgs;
    Operation op = 0;

    for (Strings::iterator i = args.begin(); i != args.end(); ++i) {
        string arg = *i;

        Operation oldOp = op;

        if (arg == "--install" || arg == "-i")
            op = opInstall;
        else if (arg == "--uninstall" || arg == "-u")
            op = opUninstall;
        else if (arg == "--query" || arg == "-q")
            op = opQuery;
        else if (arg[0] == '-')
            opFlags.push_back(arg);
        else
            opArgs.push_back(arg);

        if (oldOp && oldOp != op)
            throw UsageError("only one operation may be specified");
    }

    if (!op) throw UsageError("no operation specified");

    openDB();

    op(state, opFlags, opArgs);

    printEvalStats(state);
}


string programId = "nix-env";