package com.fasterxml.jackson.jr.ob.api;

import java.io.IOException;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonToken;
import com.fasterxml.jackson.jr.ob.impl.JSONReader;

API and base class for all "deserializer" implementations used to actually read
values of Java types from (JSON) input.
/**
 * API and base class for all "deserializer" implementations used to actually read
 * values of Java types from (JSON) input.
 */
public abstract class ValueReader
{
    
Type of values this reader will read
Since:
2.10/**
     * Type of values this reader will read
     *
     * @since 2.10
     */
    protected final Class<?> _valueType;

    protected ValueReader(Class<?> valueType) {
        _valueType = valueType;
    }

    /*
    /**********************************************************************
    /* Basic API to implement for actual read operations
    /**********************************************************************
     */

    
Method called to deserialize value of type supported by this reader, using
given parser. Parser is already positioned to the (first) token
of the value to read.
Params:
reader – Context object that allows calling other read methods for contained
    values of different types (for example for collection readers).
p – Underlying parser used for reading decoded token stream/**
     * Method called to deserialize value of type supported by this reader, using
     * given parser. Parser is already positioned to the (first) token
     * of the value to read.
     *
     * @param reader Context object that allows calling other read methods for contained
     *     values of different types (for example for collection readers).
     * @param p Underlying parser used for reading decoded token stream
     */
    public abstract Object read(JSONReader reader, JsonParser p) throws IOException;

    
Method called to deserialize value of type supported by this reader, using
given parser. Parser is not yet positioned to the (first) token
of the value to read and needs to be advanced.
 Default implementation simply calls `p.nextToken()` first, then calls {#link read(JSONReader, JsonParser), but some implementations may decide to implement this differently to use (slightly) more efficient accessor in JsonParser, like JsonParser.nextIntValue(int). 
Params:
reader – Context object that allows calling other read methods for contained
    values of different types (for example for collection readers).
p – Underlying parser used for reading decoded token stream/**
     * Method called to deserialize value of type supported by this reader, using
     * given parser. Parser is not yet positioned to the (first) token
     * of the value to read and needs to be advanced.
     *<p>
     * Default implementation simply calls `p.nextToken()` first, then calls
     * {#link {@link #read(JSONReader, JsonParser)}, but some implementations
     * may decide to implement this differently to use (slightly) more efficient
     * accessor in {@link JsonParser}, like {@link JsonParser#nextIntValue(int)}.
     *
     * @param reader Context object that allows calling other read methods for contained
     *     values of different types (for example for collection readers).
     * @param p Underlying parser used for reading decoded token stream
     */
    public Object readNext(JSONReader reader, JsonParser p) throws IOException {
        p.nextToken();
        return read(reader, p);
    }

    /*
    /**********************************************************************
    /* Minimal metadata
    /**********************************************************************
     */

    
Accessor for non-generic (type-erased) type of values this reader
produces from input.
Since:
2.10/**
     * Accessor for non-generic (type-erased) type of values this reader
     * produces from input.
     *
     * @since 2.10
     */
    public Class<?> valueType() {
        return _valueType;
    }

    /*
    /**********************************************************************
    /* Helper methods for sub-classes
    /**********************************************************************
     */

    
Helper method for getting description of the token parser currently points to,
for use in descriptions and exception messages.
/**
     * Helper method for getting description of the token parser currently points to,
     * for use in descriptions and exception messages.
     */
    public static String _tokenDesc(JsonParser p) throws IOException {
        return _tokenDesc(p, p.currentToken());
    }

    
Helper method for getting description of given token
for use in descriptions and exception messages.
/**
     * Helper method for getting description of given token
     * for use in descriptions and exception messages.
     */
    public static String _tokenDesc(JsonParser p, JsonToken t) throws IOException {
        if (t == null) {
            return "NULL";
        }
        switch (t) {
        case FIELD_NAME:
            return "JSON Field name '"+p.getCurrentName()+"'";
        case START_ARRAY:
            return "JSON Array";
        case START_OBJECT:
            return "JSON Object";
        case VALUE_FALSE:
            return "`false`";
        case VALUE_NULL:
            return "'null'";
        case VALUE_NUMBER_FLOAT:
        case VALUE_NUMBER_INT:
            return "JSON Number";
        case VALUE_STRING:
            return "JSON String";
        case VALUE_TRUE:
            return "`true`";
        case VALUE_EMBEDDED_OBJECT:
            {
                final Object value = p.getEmbeddedObject();
                if (value == null) {
                    return "EMBEDDED_OBJECT `null`";
                }
                return "EMBEDDED_OBJECT of type "+p.getClass().getName();
            }
        default:
            return t.toString();
        }
    }
}