/*
 * Copyright (c) 2013 Yaroslav Stavnichiy <yarosla@gmail.com>
 *
 * This file is part of NXJSON.
 *
 * NXJSON is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation, either version 3
 * of the License, or (at your option) any later version.
 *
 * NXJSON is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with NXJSON. If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <malloc.h>
#include <assert.h>

#include "nxjson.h"

// redefine NX_JSON_CALLOC & NX_JSON_FREE to use custom allocator
#ifndef NX_JSON_CALLOC
#define NX_JSON_CALLOC() calloc(1, sizeof(nx_json))
#define NX_JSON_FREE(json) free((void*)(json))
#endif

#ifdef __ANDROID__
#  include <jni.h>
#  include <android/log.h>
#  define NX_JSON_REPORT_ERROR(msg, p) __android_log_print(ANDROID_LOG_ERROR, "nxjson", "NXJSON PARSE ERROR (%d): " msg " at %s\n", __LINE__, p)
#endif

// redefine NX_JSON_REPORT_ERROR to use custom error reporting
#ifndef NX_JSON_REPORT_ERROR
#define NX_JSON_REPORT_ERROR(msg, p) fprintf(stderr, "NXJSON PARSE ERROR (%d): " msg " at %s\n", __LINE__, p)
#endif

#define IS_WHITESPACE(c) ((unsigned char)(c)<=(unsigned char)' ')

static const nx_json dummy={ NX_JSON_NULL };

static nx_json* create_json(nx_json_type type, const char* key, nx_json* parent) {
    nx_json* js=NX_JSON_CALLOC();
    assert(js);
    js->type=type;
    js->key=key;
    if (!parent->last_child) {
        parent->child=parent->last_child=js;
    }
    else {
        parent->last_child->next=js;
        parent->last_child=js;
    }
    parent->length++;
    return js;
}

void nx_json_free(const nx_json* js) {
    nx_json* p=js->child;
    nx_json* p1;
    while (p) {
        p1=p->next;
        nx_json_free(p);
        p=p1;
    }
    NX_JSON_FREE(js);
}

static int unicode_to_utf8(unsigned int codepoint, char* p, char** endp) {
    // code from http://stackoverflow.com/a/4609989/697313
    if (codepoint<0x80) *p++=codepoint;
    else if (codepoint<0x800) *p++=192+codepoint/64, *p++=128+codepoint%64;
    else if (codepoint-0xd800u<0x800) return 0; // surrogate must have been treated earlier
    else if (codepoint<0x10000) *p++=224+codepoint/4096, *p++=128+codepoint/64%64, *p++=128+codepoint%64;
    else if (codepoint<0x110000) *p++=240+codepoint/262144, *p++=128+codepoint/4096%64, *p++=128+codepoint/64%64, *p++=128+codepoint%64;
    else return 0; // error
    *endp=p;
    return 1;
}

nx_json_unicode_encoder nx_json_unicode_to_utf8=unicode_to_utf8;

static inline int hex_val(char c) {
    if (c>='0' && c<='9') return c-'0';
    if (c>='a' && c<='f') return c-'a'+10;
    if (c>='A' && c<='F') return c-'A'+10;
    return -1;
}

static char* unescape_string(char* s, char** end, nx_json_unicode_encoder encoder) {
    char* p=s;
    char* d=s;
    char c;
    while ((c=*p++)) {
        if (c=='"') {
            *d='\0';
            *end=p;
            return s;
        }
        else if (c=='\\') {
            switch (*p) {
                case '\\':
                case '/':
                case '"':
                    *d++=*p++;
                    break;
                case 'b':
                    *d++='\b'; p++;
                    break;
                case 'f':
                    *d++='\f'; p++;
                    break;
                case 'n':
                    *d++='\n'; p++;
                    break;
                case 'r':
                    *d++='\r'; p++;
                    break;
                case 't':
                    *d++='\t'; p++;
                    break;
                case 'u': // unicode
                    if (!encoder) {
                        // leave untouched
                        *d++=c;
                        break;
                    }
                    char* ps=p-1;
                    int h1, h2, h3, h4;
                    if ((h1=hex_val(p[1]))<0 || (h2=hex_val(p[2]))<0 || (h3=hex_val(p[3]))<0 || (h4=hex_val(p[4]))<0) {
                        NX_JSON_REPORT_ERROR("invalid unicode escape", p-1);
                        return 0;
                    }
                    unsigned int codepoint=h1<<12|h2<<8|h3<<4|h4;
                    if ((codepoint & 0xfc00)==0xd800) { // high surrogate; need one more unicode to succeed
                        p+=6;
                        if (p[-1]!='\\' || *p!='u' || (h1=hex_val(p[1]))<0 || (h2=hex_val(p[2]))<0 || (h3=hex_val(p[3]))<0 || (h4=hex_val(p[4]))<0) {
                            NX_JSON_REPORT_ERROR("invalid unicode surrogate", ps);
                            return 0;
                        }
                        unsigned int codepoint2=h1<<12|h2<<8|h3<<4|h4;
                        if ((codepoint2 & 0xfc00)!=0xdc00) {
                            NX_JSON_REPORT_ERROR("invalid unicode surrogate", ps);
                            return 0;
                        }
                        codepoint=0x10000+((codepoint-0xd800)<<10)+(codepoint2-0xdc00);
                    }
                    if (!encoder(codepoint, d, &d)) {
                        NX_JSON_REPORT_ERROR("invalid codepoint", ps);
                        return 0;
                    }
                    p+=5;
                    break;
                default:
                    // leave untouched
                    *d++=c;
                    break;
            }
        }
        else {
            *d++=c;
        }
    }
    NX_JSON_REPORT_ERROR("no closing quote for string", s);
    return 0;
}

static char* skip_block_comment(char* p) {
    // assume p[-2]=='/' && p[-1]=='*'
    char* ps=p-2;
    if (!*p) {
        NX_JSON_REPORT_ERROR("endless comment", ps);
        return 0;
    }
REPEAT:
    p=strchr(p+1, '/');
    if (!p) {
        NX_JSON_REPORT_ERROR("endless comment", ps);
        return 0;
    }
    if (p[-1]!='*') goto REPEAT;
    return p+1;
}

static char* parse_key(const char** key, char* p, nx_json_unicode_encoder encoder) {
    // on '}' return with *p=='}'
    char c;
    while ((c=*p++)) {
        if (c=='"') {
            *key=unescape_string(p, &p, encoder);
            if (!*key) return 0; // propagate error
            while (*p && IS_WHITESPACE(*p)) p++;
            if (*p==':') return p+1;
            NX_JSON_REPORT_ERROR("unexpected chars", p);
            return 0;
        }
        else if (IS_WHITESPACE(c) || c==',') {
            // continue
        }
        else if (c=='}') {
            return p-1;
        }
        else if (c=='/') {
            if (*p=='/') { // line comment
                char* ps=p-1;
                p=strchr(p+1, '\n');
                if (!p) {
                    NX_JSON_REPORT_ERROR("endless comment", ps);
                    return 0; // error
                }
                p++;
            }
            else if (*p=='*') { // block comment
                p=skip_block_comment(p+1);
                if (!p) return 0;
            }
            else {
                NX_JSON_REPORT_ERROR("unexpected chars", p-1);
                return 0; // error
            }
        }
        else {
            NX_JSON_REPORT_ERROR("unexpected chars", p-1);
            return 0; // error
        }
    }
    NX_JSON_REPORT_ERROR("unexpected chars", p-1);
    return 0; // error
}

static char* parse_value(nx_json* parent, const char* key, char* p, nx_json_unicode_encoder encoder) {
    nx_json* js;
    while (1) {
        switch (*p) {
            case '\0':
                NX_JSON_REPORT_ERROR("unexpected end of text", p);
                return 0; // error
            case ' ': case '\t': case '\n': case '\r':
            case ',':
                // skip
                p++;
                break;
            case '{':
                js=create_json(NX_JSON_OBJECT, key, parent);
                p++;
                while (1) {
                    const char* new_key;
                    p=parse_key(&new_key, p, encoder);
                    if (!p) return 0; // error
                    if (*p=='}') return p+1; // end of object
                    p=parse_value(js, new_key, p, encoder);
                    if (!p) return 0; // error
                }
            case '[':
                js=create_json(NX_JSON_ARRAY, key, parent);
                p++;
                while (1) {
                    p=parse_value(js, 0, p, encoder);
                    if (!p) return 0; // error
                    if (*p==']') return p+1; // end of array
                }
            case ']':
                return p;
            case '"':
                p++;
                js=create_json(NX_JSON_STRING, key, parent);
                js->text_value=unescape_string(p, &p, encoder);
                if (!js->text_value) return 0; // propagate error
                return p;
            case '-': case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9':
            {
                js=create_json(NX_JSON_INTEGER, key, parent);
                char* pe;
                js->int_value=strtol(p, &pe, 0);
                if (pe==p) {
                    NX_JSON_REPORT_ERROR("invalid number", p);
                    return 0; // error
                }
                if (*pe=='.' || *pe=='e' || *pe=='E') { // double value
                    js->type=NX_JSON_DOUBLE;
                    js->dbl_value=strtod(p, &pe);
                    if (pe==p) {
                        NX_JSON_REPORT_ERROR("invalid number", p);
                        return 0; // error
                    }
                }
                else {
                    js->dbl_value=js->int_value;
                }
                return pe;
            }
            case 't':
                if (!strncmp(p, "true", 4)) {
                    js=create_json(NX_JSON_BOOL, key, parent);
                    js->int_value=1;
                    return p+4;
                }
                NX_JSON_REPORT_ERROR("unexpected chars", p);
                return 0; // error
            case 'f':
                if (!strncmp(p, "false", 5)) {
                    js=create_json(NX_JSON_BOOL, key, parent);
                    js->int_value=0;
                    return p+5;
                }
                NX_JSON_REPORT_ERROR("unexpected chars", p);
                return 0; // error
            case 'n':
                if (!strncmp(p, "null", 4)) {
                    create_json(NX_JSON_NULL, key, parent);
                    return p+4;
                }
                NX_JSON_REPORT_ERROR("unexpected chars", p);
                return 0; // error
            case '/': // comment
                if (p[1]=='/') { // line comment
                    char* ps=p;
                    p=strchr(p+2, '\n');
                    if (!p) {
                        NX_JSON_REPORT_ERROR("endless comment", ps);
                        return 0; // error
                    }
                    p++;
                }
                else if (p[1]=='*') { // block comment
                    p=skip_block_comment(p+2);
                    if (!p) return 0;
                }
                else {
                    NX_JSON_REPORT_ERROR("unexpected chars", p);
                    return 0; // error
                }
                break;
            default:
                NX_JSON_REPORT_ERROR("unexpected chars", p);
                return 0; // error
        }
    }
}

const nx_json* nx_json_parse_utf8(char* text) {
    return nx_json_parse(text, unicode_to_utf8);
}

const nx_json* nx_json_parse(char* text, nx_json_unicode_encoder encoder) {
    nx_json js={0};
    if (!parse_value(&js, 0, text, encoder)) {
        if (js.child) nx_json_free(js.child);
        return 0;
    }
    return js.child;
}

const nx_json* nx_json_get(const nx_json* json, const char* key) {
    if (!json || !key) return &dummy; // never return null
    nx_json* js;
    for (js=json->child; js; js=js->next) {
        if (js->key && !strcmp(js->key, key)) return js;
    }
    return &dummy; // never return null
}

const nx_json* nx_json_item(const nx_json* json, int idx) {
    if (!json) return &dummy; // never return null
    nx_json* js;
    for (js=json->child; js; js=js->next) {
        if (!idx--) return js;
    }
    return &dummy; // never return null
}
