package com.jsoniter;

import com.jsoniter.spi.*;
import javassist.ClassPool;
import javassist.CtClass;
import javassist.CtMethod;
import javassist.CtNewMethod;

import java.lang.reflect.*;
import java.util.*;

class Codegen {
    static boolean strictMode = false;
    static ClassPool pool = ClassPool.getDefault();

    public static void enableStrictMode() {
        strictMode = true;
    }

    static Decoder getDecoder(String cacheKey, Type type) {
        Decoder decoder = ExtensionManager.getDecoder(cacheKey);
        if (decoder != null) {
            return decoder;
        }
        return gen(cacheKey, type);
    }

    private synchronized static Decoder gen(String cacheKey, Type type) {
        Decoder decoder = ExtensionManager.getDecoder(cacheKey);
        if (decoder != null) {
            return decoder;
        }
        for (Extension extension : ExtensionManager.getExtensions()) {
            decoder = extension.createDecoder(cacheKey, type);
            if (decoder != null) {
                ExtensionManager.addNewDecoder(cacheKey, decoder);
                return decoder;
            }
        }
        Type[] typeArgs = new Type[0];
        Class clazz;
        if (type instanceof ParameterizedType) {
            ParameterizedType pType = (ParameterizedType) type;
            clazz = (Class) pType.getRawType();
            typeArgs = pType.getActualTypeArguments();
        } else {
            clazz = (Class) type;
        }
        String source = genSource(cacheKey, clazz, typeArgs);
        if ("true".equals(System.getenv("JSONITER_DEBUG"))) {
            System.out.println(">>> " + cacheKey);
            System.out.println(source);
        }
        try {
            CtClass ctClass = pool.makeClass(cacheKey);
            ctClass.setInterfaces(new CtClass[]{pool.get(Decoder.class.getName())});
            CtMethod staticMethod = CtNewMethod.make(source, ctClass);
            ctClass.addMethod(staticMethod);
            CtMethod interfaceMethod = CtNewMethod.make("" +
                    "public Object decode(com.jsoniter.JsonIterator iter) {" +
                    "return decode_(iter);" +
                    "}", ctClass);
            ctClass.addMethod(interfaceMethod);
            decoder = (Decoder) ctClass.toClass().newInstance();
            ExtensionManager.addNewDecoder(cacheKey, decoder);
            return decoder;
        } catch (Exception e) {
            System.err.println("failed to generate decoder for: " + type + " with " + Arrays.toString(typeArgs));
            System.err.println(source);
            throw new JsonException(e);
        }
    }

    private static String genSource(String cacheKey, Class clazz, Type[] typeArgs) {
        if (CodegenImplNative.NATIVE_READS.containsKey(clazz.getName())) {
            return CodegenImplNative.genNative(clazz.getName());
        }
        if (clazz.isArray()) {
            return CodegenImplArray.genArray(clazz);
        }
        if (Map.class.isAssignableFrom(clazz)) {
            return CodegenImplMap.genMap(clazz, typeArgs);
        }
        if (Collection.class.isAssignableFrom(clazz)) {
            return CodegenImplArray.genCollection(clazz, typeArgs);
        }
        ClassDescriptor desc = ExtensionManager.getClassDescriptor(clazz, false);
        List<Binding> allBindings = desc.allDecoderBindings();
        for (Binding binding : allBindings) {
            if (binding.failOnMissing || binding.failOnPresent) {
                // only slice support mandatory tracking
                return CodegenImplObject.genObjectUsingSlice(clazz, cacheKey, desc);
            }
        }
        if (desc.failOnUnknownFields) {
            // only slice support unknown field tracking
            return CodegenImplObject.genObjectUsingSlice(clazz, cacheKey, desc);
        }
        if (allBindings.isEmpty()) {
            return CodegenImplObject.genObjectUsingSkip(clazz, desc.ctor);
        }
        if (strictMode) {
            return CodegenImplObject.genObjectUsingSlice(clazz, cacheKey, desc);
        }
        return CodegenImplObject.genObjectUsingHash(clazz, cacheKey, desc);
    }
}