#include "config.h"
#include "json-to-value.hh"

#include <cstring>

namespace nix {


static void skipWhitespace(const char * & s)
{
    while (*s == ' ' || *s == '\t' || *s == '\n' || *s == '\r') s++;
}


#if HAVE_BOEHMGC
typedef std::vector<Value *, gc_allocator<Value *> > ValueVector;
#else
typedef std::vector<Value *> ValueVector;
#endif


static string parseJSONString(const char * & s)
{
    string res;
    if (*s++ != '"') throw JSONParseError("expected JSON string");
    while (*s != '"') {
        if (!*s) throw JSONParseError("got end-of-string in JSON string");
        if (*s == '\\') {
            s++;
            if (*s == '"') res += '"';
            else if (*s == '\\') res += '\\';
            else if (*s == '/') res += '/';
            else if (*s == '/') res += '/';
            else if (*s == 'b') res += '\b';
            else if (*s == 'f') res += '\f';
            else if (*s == 'n') res += '\n';
            else if (*s == 'r') res += '\r';
            else if (*s == 't') res += '\t';
            else if (*s == 'u') throw JSONParseError("\\u characters in JSON strings are currently not supported");
            else throw JSONParseError("invalid escaped character in JSON string");
            s++;
        } else
            res += *s++;
    }
    s++;
    return res;
}


static void parseJSON(EvalState & state, const char * & s, Value & v)
{
    skipWhitespace(s);

    if (!*s) throw JSONParseError("expected JSON value");

    if (*s == '[') {
        s++;
        ValueVector values;
        values.reserve(128);
        skipWhitespace(s);
        while (1) {
            if (values.empty() && *s == ']') break;
            Value * v2 = state.allocValue();
            parseJSON(state, s, *v2);
            values.push_back(v2);
            skipWhitespace(s);
            if (*s == ']') break;
            if (*s != ',') throw JSONParseError("expected ‘,’ or ‘]’ after JSON array element");
            s++;
        }
        s++;
        state.mkList(v, values.size());
        for (size_t n = 0; n < values.size(); ++n)
            v.list.elems[n] = values[n];
    }

    else if (*s == '{') {
        s++;
        state.mkAttrs(v, 1);
        while (1) {
            skipWhitespace(s);
            if (v.attrs->empty() && *s == '}') break;
            string name = parseJSONString(s);
            skipWhitespace(s);
            if (*s != ':') throw JSONParseError("expected ‘:’ in JSON object");
            s++;
            Value * v2 = state.allocValue();
            parseJSON(state, s, *v2);
            v.attrs->push_back(Attr(state.symbols.create(name), v2));
            skipWhitespace(s);
            if (*s == '}') break;
            if (*s != ',') throw JSONParseError("expected ‘,’ or ‘}’ after JSON member");
            s++;
        }
        v.attrs->sort();
        s++;
    }

    else if (*s == '"') {
        mkString(v, parseJSONString(s));
    }

    else if (isdigit(*s) || *s == '-') {
        bool neg = false;
        if (*s == '-') {
            neg = true;
            if (!*++s) throw JSONParseError("unexpected end of JSON number");
        }
        NixInt n = 0;
        // FIXME: detect overflow
        while (isdigit(*s)) n = n * 10 + (*s++ - '0');
        if (*s == '.' || *s == 'e') throw JSONParseError("floating point JSON numbers are not supported");
        mkInt(v, neg ? -n : n);
    }

    else if (strncmp(s, "true", 4) == 0) {
        s += 4;
        mkBool(v, true);
    }

    else if (strncmp(s, "false", 5) == 0) {
        s += 5;
        mkBool(v, false);
    }

    else if (strncmp(s, "null", 4) == 0) {
        s += 4;
        mkNull(v);
    }

    else throw JSONParseError("unrecognised JSON value");
}


void parseJSON(EvalState & state, const string & s_, Value & v)
{
    const char * s = s_.c_str();
    parseJSON(state, s, v);
    skipWhitespace(s);
    if (*s) throw JSONParseError(format("expected end-of-string while parsing JSON value: %1%") % s);
}


}