package xsdvalidate

/*
#cgo CFLAGS: -std=c99
#cgo pkg-config: libxml-2.0
#include <string.h>
#include <sys/time.h>
#include <errno.h>
#include <libxml/xmlschemastypes.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#define GO_ERR_INIT 1024
#define P_ERR_DEFAULT 1
#define P_ERR_VERBOSE 2
#define P_XML_HUGE 4
#define LIBXML_STATIC
#define NOOP ((void)0)

struct xsdParserResult {
    xmlSchemaPtr schemaPtr;
    char* errorStr;
};

struct xmlParserResult {
    xmlDocPtr docPtr;
    char* errorStr;
};

typedef enum {
    NO_ERROR = 0,
    LIBXML2_ERROR = 1,
    XSD_PARSER_ERROR = 2,
    XML_PARSER_ERROR = 3,
    VALIDATION_ERROR = 4
} errorType;

struct simpleXmlError {
    errorType type;
    int code;
    char* message;
    int level;
    int line;
    char* node;
};

typedef struct _errArray {
    struct simpleXmlError* data;
    size_t len;
    size_t cap;
} errArray;

typedef struct _errCtx {
    char* errBuf;
    size_t len;
    size_t cap;
} errCtx;

static errArray initErrArray() {
    errArray errArr = {
        .data = calloc(2, sizeof(struct simpleXmlError)), .len = 0, .cap = 2};
    return errArr;
}

static void freeErrArray(errArray* errArr) {
    for (int i = 0; i < errArr->len; i++) {
        free(errArr->data[i].message);
        free(errArr->data[i].node);
    }
    free(errArr->data);
}

static errCtx initErrCtx(size_t len, size_t cap) {
    errCtx ectx = {.errBuf = malloc(cap), .len = len, .cap = cap};
    memset(ectx.errBuf, '\0', len);
    return ectx;
}

static void freeErrCtx(errCtx ectx) {
    free(ectx.errBuf);
    ectx.len=0;
    ectx.cap=0;
}

static void appendErrCtxErrBuff(errCtx* ectx, const char* buffStr) {
    size_t buffStrLen = strlen(buffStr);
    size_t capWanted = ectx->len + buffStrLen;

    if (capWanted > ectx->cap) {
        size_t newCap = capWanted + GO_ERR_INIT;
        char* tmp = malloc(newCap);
        memcpy(tmp, ectx->errBuf, ectx->len);
        free(ectx->errBuf);
        ectx->errBuf = tmp;
        ectx->cap = newCap;
    }

    size_t newLen = ectx->len + buffStrLen;
    char* tmp = malloc(newLen);
    if (ectx->len > 1) {
        memcpy(tmp, ectx->errBuf, ectx->len);
    }
    memcpy(&tmp[ectx->len - 1], buffStr, buffStrLen + 1);
    // strcat(tmp, newLine);
    free(ectx->errBuf);
    ectx->errBuf = tmp;
    ectx->len = newLen;
}

static void noOutputCallback(void* ctx, const char* message, ...) {}

static void init() {
    xmlInitParser();
}

static void cleanup() {
#if LIBXML_VERSION < 21000
    xmlSchemaCleanupTypes();
#endif
    xmlCleanupParser();
}

static void genErrorCallback(void* ctx, const char* message, ...) {
    errCtx* ectx = ctx;
    char* newLine = malloc(GO_ERR_INIT);

    va_list varArgs;
    va_start(varArgs, message);

    size_t lineLen = 1 + vsnprintf(newLine, GO_ERR_INIT, message, varArgs);

    if (lineLen > GO_ERR_INIT) {
        va_end(varArgs);
        va_start(varArgs, message);
        free(newLine);
        newLine = malloc(lineLen);
        vsnprintf(newLine, lineLen, message, varArgs);
        va_end(varArgs);
    } else {
        va_end(varArgs);
    }

    appendErrCtxErrBuff(ectx, newLine);
    free(newLine);
}

static void simpleStructErrorCallback(
    void* ctx,
#if LIBXML_VERSION >= 21200
    const xmlError *p
#else
    xmlErrorPtr p
#endif
) {
    errArray* sErrArr = ctx;

    struct simpleXmlError sErr;
    sErr.message = calloc(GO_ERR_INIT, sizeof(char));
    sErr.node = calloc(GO_ERR_INIT, sizeof(char));

    sErr.type = VALIDATION_ERROR;
    sErr.code = p->code;
    sErr.level = p->level;
    sErr.line = p->line;

    int cpyLen = 1 + snprintf(sErr.message, GO_ERR_INIT, "%s", p->message);
    if (cpyLen > GO_ERR_INIT) {
        free(sErr.message);
        sErr.message = malloc(cpyLen);
        snprintf(sErr.message, cpyLen, "%s", p->message);
    }

    if (p->node != NULL) {
        cpyLen = 1 + snprintf(sErr.node, GO_ERR_INIT, "%s",
                              (((xmlNodePtr)p->node)->name));
        if (cpyLen > GO_ERR_INIT) {
            free(sErr.node);
            sErr.node = malloc(cpyLen);
            snprintf(sErr.node, cpyLen, "%s", (((xmlNodePtr)p->node)->name));
        }
    }
    if (sErrArr->len >= sErrArr->cap) {
        sErrArr->cap = sErrArr->cap * 2;
        struct simpleXmlError* tmp = calloc(sErrArr->cap, sizeof(*tmp));
        memcpy(tmp, sErrArr->data, sErrArr->len * sizeof(*tmp));
        free(sErrArr->data);
        sErrArr->data = tmp;
    }
    sErrArr->data[sErrArr->len] = sErr;
    sErrArr->len++;
}

static struct xsdParserResult parseSchema(
                                          xmlSchemaParserCtxtPtr schemaParserCtxt,
                                          const short int options) {
    bool err = false;
    struct xsdParserResult parserResult;
    errCtx ectx = initErrCtx(1, GO_ERR_INIT);
    errCtx ectxParse = initErrCtx(1, GO_ERR_INIT);

    xmlSchemaPtr schema = NULL;

    if (schemaParserCtxt == NULL) {
        err = true;
        const char msg[] = "Xsd parser internal error";
        freeErrCtx(ectxParse);
        appendErrCtxErrBuff(&ectx, msg);
    } else {
        if (options & P_ERR_VERBOSE) {
            xmlSchemaSetParserErrors(schemaParserCtxt, genErrorCallback, noOutputCallback, &ectxParse);
            xmlSetGenericErrorFunc(&ectx, genErrorCallback);
        } else {
            xmlSetGenericErrorFunc(NULL, noOutputCallback);
            xmlSchemaSetParserErrors(schemaParserCtxt, genErrorCallback, noOutputCallback, &ectx);
        }

        schema = xmlSchemaParse(schemaParserCtxt);

        xmlSchemaFreeParserCtxt(schemaParserCtxt);
        if (schema == NULL) {
            freeErrCtx(ectx);
            ectx = ectxParse;
            err = true;
        } else {
            freeErrCtx(ectxParse);
        }
    }

    parserResult.errorStr = malloc(ectx.len);
    memcpy(parserResult.errorStr, ectx.errBuf, ectx.len);
    freeErrCtx(ectx);
    parserResult.schemaPtr = schema;
    errno = err ? -1 : 0;
    return parserResult;
}

static struct xsdParserResult cParseUrlSchema(const char* url,
                                              const short int options) {
    xmlSchemaParserCtxtPtr schemaParserCtxt = NULL;
    schemaParserCtxt = xmlSchemaNewParserCtxt(url);
    return parseSchema(schemaParserCtxt, options);
}

static struct xsdParserResult cParseMemSchema(const void* xsd,
                                              const int goXsdSourceLen,
                                              const short int options) {
    xmlSchemaParserCtxtPtr schemaParserCtxt = NULL;
    schemaParserCtxt = xmlSchemaNewMemParserCtxt(xsd, goXsdSourceLen);

    return parseSchema(schemaParserCtxt, options);
}

static int getLibxmlOptions(short int options) {
    int xmlParserOptions = 0;

    if (options & P_XML_HUGE) {
        xmlParserOptions |= XML_PARSE_HUGE;
    }

    return xmlParserOptions;
}

static struct xmlParserResult cParseDoc(const void* goXmlSource,
                                        const int goXmlSourceLen,
                                        const short int options) {
    bool err = false;
    struct xmlParserResult parserResult;
    errCtx ectx = initErrCtx(1, GO_ERR_INIT);

    xmlDocPtr doc = NULL;
    xmlParserCtxtPtr xmlParserCtxt = NULL;

    if (goXmlSourceLen == 0) {
        err = true;
        if (options & P_ERR_VERBOSE) {
            const char msg[] = "parser error : Document is empty";
            appendErrCtxErrBuff(&ectx, msg);
        } else {
            const char msg[] = "Malformed xml document";
            appendErrCtxErrBuff(&ectx, msg);
        }
    } else {
        xmlParserCtxt = xmlNewParserCtxt();

        if (xmlParserCtxt == NULL) {
            err = true;
            const char msg[] = "Xml parser internal error";
            appendErrCtxErrBuff(&ectx, msg);
        } else {
            if (options & P_ERR_VERBOSE) {
                xmlSetGenericErrorFunc(&ectx, genErrorCallback);
            } else {
                xmlSetGenericErrorFunc(NULL, noOutputCallback);
            }

            int xmlParserOptions = getLibxmlOptions(options);
            doc = xmlCtxtReadMemory(xmlParserCtxt, goXmlSource, goXmlSourceLen, NULL, NULL, xmlParserOptions);

            xmlFreeParserCtxt(xmlParserCtxt);
            if (doc == NULL) {
                err = true;
                if (!(options & P_ERR_VERBOSE)) {
                    const char msg[] = "Malformed xml document";
                    appendErrCtxErrBuff(&ectx, msg);
                }
            }
        }
    }

    parserResult.errorStr = malloc(ectx.len);
    memcpy(parserResult.errorStr, ectx.errBuf, ectx.len);
    freeErrCtx(ectx);
    parserResult.docPtr = doc;
    errno = err ? -1 : 0;
    return parserResult;
}

static errArray cValidate(const xmlDocPtr doc, const xmlSchemaPtr schema) {
    errArray errArr = initErrArray();

    struct simpleXmlError simpleError;
    simpleError.message = calloc(GO_ERR_INIT, sizeof(char));
    simpleError.node = calloc(GO_ERR_INIT, sizeof(char));

    if (schema == NULL) {
        simpleError.type = LIBXML2_ERROR;
        strcpy(simpleError.message, "Xsd schema null pointer");
        errArr.data[errArr.len] = simpleError;
        errArr.len++;
    } else if (doc == NULL) {
        simpleError.type = LIBXML2_ERROR;
        strcpy(simpleError.message, "Xml doc null pointer");
        errArr.data[errArr.len] = simpleError;
        errArr.len++;
    } else {
        xmlSchemaValidCtxtPtr schemaCtxt;
        schemaCtxt = xmlSchemaNewValidCtxt(schema);

        if (schemaCtxt == NULL) {
            simpleError.type = LIBXML2_ERROR;
            strcpy(simpleError.message, "Xml validation internal error");
            errArr.data[errArr.len] = simpleError;
            errArr.len++;
        } else {
            xmlSchemaSetValidStructuredErrors(schemaCtxt, simpleStructErrorCallback,
                                              &errArr);
            int schemaErr = xmlSchemaValidateDoc(schemaCtxt, doc);
            xmlSchemaFreeValidCtxt(schemaCtxt);

            if (schemaErr < 0 && errArr.len == 0) {
                simpleError.type = LIBXML2_ERROR;
                strcpy(simpleError.message, "Xml validation internal error");
                errArr.data[errArr.len] = simpleError;
                errArr.len++;
            } else {
                free(simpleError.node);
                free(simpleError.message);
            }
        }
    }

    errno = errArr.len == NO_ERROR ? 0 : -1;
    return errArr;
}

static errArray cValidateBuf(const void* goXmlSource,
                             const int goXmlSourceLen,
                             const short int xmlParserOptions,
                             const xmlSchemaPtr schema) {
    errArray errArr = initErrArray();

    struct simpleXmlError simpleError;
    simpleError.message = calloc(GO_ERR_INIT, sizeof(char));
    simpleError.node = calloc(GO_ERR_INIT, sizeof(char));

    struct xmlParserResult parserResult =
    cParseDoc(goXmlSource, goXmlSourceLen, xmlParserOptions);

    if (schema == NULL) {
        simpleError.type = LIBXML2_ERROR;
        const char msg[] = "Xsd schema null pointer";
        strcpy(simpleError.message, msg);
        errArr.data[errArr.len] = simpleError;
        errArr.len++;

        xmlFreeDoc(parserResult.docPtr);
        free(parserResult.errorStr);
        errno = -1;
        return errArr;
    } else if (parserResult.docPtr == NULL) {
        simpleError.type = XML_PARSER_ERROR;
        free(simpleError.message);
        simpleError.message = malloc(strlen(parserResult.errorStr) + 1);
        strcpy(simpleError.message, parserResult.errorStr);
        errArr.data[errArr.len] = simpleError;
        errArr.len++;

        xmlFreeDoc(parserResult.docPtr);
        free(parserResult.errorStr);
        errno = -1;
        return errArr;
    }
    free(simpleError.node);
    free(simpleError.message);
    freeErrArray(&errArr);
    free(parserResult.errorStr);

    errArray valErrArr = cValidate(parserResult.docPtr, schema);

    xmlFreeDoc(parserResult.docPtr);

    errno = valErrArr.len == NO_ERROR ? 0 : -1;
    return valErrArr;
}
*/
import "C"
import (
	"runtime"
	"strings"
	"time"
	"unsafe"
)

// XsdHandler handles schema parsing and validation and wraps a pointer to libxml2's xmlSchemaPtr.
type XsdHandler struct {
	schemaPtr C.xmlSchemaPtr
}

// XmlHandler handles xml parsing and wraps a pointer to libxml2's xmlDocPtr.
type XmlHandler struct {
	docPtr C.xmlDocPtr
}

// Initializes the libxml2 parser, suggested for multithreading
func libXml2Init() {
	C.init()
}

// Cleans up the libxml2 parser
func libXml2Cleanup() {
	C.cleanup()
}

// The helper function for parsing xml
func parseXmlMem(inXml []byte, options Options) (C.xmlDocPtr, error) {
	strXml := C.CBytes(inXml)
	defer C.free(unsafe.Pointer(strXml))
	pRes, err := C.cParseDoc(strXml, C.int(len(inXml)), C.short(options))

	defer C.free(unsafe.Pointer(pRes.errorStr))
	if err != nil {
		rStr := C.GoString(pRes.errorStr)
		return nil, XmlParserError{errorMessage{strings.Trim(rStr, "\n")}}
	}
	return pRes.docPtr, nil
}

// The helper function for parsing the schema
func parseUrlSchema(url string, options Options) (C.xmlSchemaPtr, error) {
	strUrl := C.CString(url)
	defer C.free(unsafe.Pointer(strUrl))

	pRes, err := C.cParseUrlSchema(strUrl, C.short(options))
	defer C.free(unsafe.Pointer(pRes.errorStr))
	if err != nil {
		rStr := C.GoString(pRes.errorStr)
		return nil, XsdParserError{errorMessage{strings.Trim(rStr, "\n")}}
	}
	return pRes.schemaPtr, nil
}

// The helper function for parsing an in-memory schema
func parseMemSchema(xsd []byte, options Options) (C.xmlSchemaPtr, error) {
	strXsd := C.CBytes(xsd)
	defer C.free(unsafe.Pointer(strXsd))

	pRes, err := C.cParseMemSchema(strXsd, C.int(len(xsd)), C.short(options))
	defer C.free(unsafe.Pointer(pRes.errorStr))
	if err != nil {
		rStr := C.GoString(pRes.errorStr)
		return nil, XsdParserError{errorMessage{strings.Trim(rStr, "\n")}}
	}
	return pRes.schemaPtr, nil
}

func handleErrArray(errSlice []C.struct_simpleXmlError) ValidationError {
	ve := ValidationError{make([]StructError, len(errSlice))}
	for i := 0; i < len(errSlice); i++ {
		ve.Errors[i] = StructError{
			Code:     int(errSlice[i].code),
			Message:  strings.Trim(C.GoString(errSlice[i].message), "\n"),
			Level:    int(errSlice[i].level),
			Line:     int(errSlice[i].line),
			NodeName: C.GoString(errSlice[i].node)}
	}
	return ve

}

const maxSimpleXmlErrors = 1 << 20

func simpleXmlErrorSlice(errArr C.errArray) ([]C.struct_simpleXmlError, error) {
	if errArr.len > maxSimpleXmlErrors {
		return nil, Libxml2Error{errorMessage{"too many validation errors"}}
	}
	return unsafe.Slice(errArr.data, errArr.len), nil
}

// Helper function for validating given an xml document
func validateWithXsd(xmlHandler *XmlHandler, xsdHandler *XsdHandler) error {
	sErr, err := C.cValidate(xmlHandler.docPtr, xsdHandler.schemaPtr)
	defer C.freeErrArray(&sErr)
	if err != nil {
		errSlice, sliceErr := simpleXmlErrorSlice(sErr)
		if sliceErr != nil {
			return sliceErr
		}
		return handleErrArray(errSlice)
	}
	return nil
}

// Helper function for validating given an xml byte slice
func validateBufWithXsd(inXml []byte, options Options, xsdHandler *XsdHandler) error {
	strXml := C.CBytes(inXml)
	defer C.free(unsafe.Pointer(strXml))
	sErr, err := C.cValidateBuf(strXml, C.int(len(inXml)), C.short(options), xsdHandler.schemaPtr)
	defer C.freeErrArray(&sErr)
	if err != nil {
		errSlice, sliceErr := simpleXmlErrorSlice(sErr)
		if sliceErr != nil {
			return sliceErr
		}
		switch errSlice[0]._type {
		case C.VALIDATION_ERROR:
			return handleErrArray(errSlice)
		case C.XML_PARSER_ERROR:
			return XmlParserError{errorMessage{strings.Trim(C.GoString(errSlice[0].message), "\n")}}
		case C.LIBXML2_ERROR:
			return Libxml2Error{errorMessage{strings.Trim(C.GoString(errSlice[0].message), "\n")}}
		case C.XSD_PARSER_ERROR:
			return XsdParserError{errorMessage{strings.Trim(C.GoString(errSlice[0].message), "\n")}}
		default:
			return Libxml2Error{errorMessage{"Unknown error"}}
		}
		return ValidationError{}
	}
	return nil
}

// Wrapper for the xmlSchemaFree function
func freeSchemaPtr(xsdHandler *XsdHandler) {
	if xsdHandler != nil && xsdHandler.schemaPtr != nil {
		C.xmlSchemaFree(xsdHandler.schemaPtr)
		xsdHandler.schemaPtr = nil
	}
}

// Wrapper for the xmlFreeDoc function
func freeDocPtr(xmlHandler *XmlHandler) {
	if xmlHandler != nil && xmlHandler.docPtr != nil {
		C.xmlFreeDoc(xmlHandler.docPtr)
		xmlHandler.docPtr = nil
	}
}

// Ticker for gc
func gcTicker(d time.Duration, quit chan struct{}) {
	ticker := time.NewTicker(d)
	for {
		select {
		case <-ticker.C:
			runtime.GC()
			//C.malloc_trim(0)
		case <-quit:
			ticker.Stop()
			return
		}
	}
}