package zig

import (
	"fmt"
	"hash/crc32"
	"unsafe"

	"golang.org/x/text/encoding"
	"golang.org/x/text/encoding/japanese"
)

/*
#cgo linux LDFLAGS: -L"./eb/eb/.libs" -l:libeb.a -lz
#cgo linux CFLAGS: -I"./eb/"
#include "zig.h"
*/
import "C"

//export hookCallback
func hookCallback(ebBook *C.EB_Book, ebAppendix *C.EB_Appendix, container *C.void, ebHookCode C.EB_Hook_Code, argc C.int, argv *C.uint) C.EB_Error_Code {
	return 0
}

type blockType int

const (
	blockTypeHeading blockType = iota
	blockTypeText
)

type BookEntry struct {
	Heading string
	Text    string
}

type BookSubbook struct {
	Title     string
	Copyright string
	Entries   []BookEntry
}

type Book struct {
	DiscCode string
	CharCode string
	Subbooks []BookSubbook
}

type Context struct {
	buffer  []byte
	decoder *encoding.Decoder
	hookset *C.EB_Hookset
	book    *C.EB_Book
}

func (c *Context) initialize() error {
	if errEb := C.eb_initialize_library(); errEb != C.EB_SUCCESS {
		return fmt.Errorf("eb_initialize_library failed with code %d", errEb)
	}

	c.book = (*C.EB_Book)(C.calloc(1, C.ulong(unsafe.Sizeof(C.EB_Book{}))))
	C.eb_initialize_book(c.book)

	c.hookset = (*C.EB_Hookset)(C.calloc(1, C.ulong(unsafe.Sizeof(C.EB_Hookset{}))))
	C.eb_initialize_hookset(c.hookset)

	if err := c.installHooks(); err != nil {
		return err
	}

	c.buffer = make([]byte, 22)
	c.decoder = japanese.EUCJP.NewDecoder()

	return nil
}

func (c *Context) shutdown() {
	C.eb_finalize_hookset(c.hookset)
	C.free(unsafe.Pointer(c.hookset))

	C.eb_finalize_book(c.book)
	C.free(unsafe.Pointer(c.book))

	C.eb_finalize_library()
}

func (c *Context) installHooks() error {
	hookCodes := []C.EB_Hook_Code{
		C.EB_HOOK_BEGIN_CANDIDATE,
		C.EB_HOOK_BEGIN_CLICKABLE_AREA,
		C.EB_HOOK_BEGIN_COLOR_BMP,
		C.EB_HOOK_BEGIN_COLOR_JPEG,
		C.EB_HOOK_BEGIN_DECORATION,
		C.EB_HOOK_BEGIN_EBXAC_GAIJI,
		C.EB_HOOK_BEGIN_EMPHASIS,
		C.EB_HOOK_BEGIN_GRAPHIC_REFERENCE,
		C.EB_HOOK_BEGIN_GRAY_GRAPHIC,
		C.EB_HOOK_BEGIN_IMAGE_PAGE,
		C.EB_HOOK_BEGIN_IN_COLOR_BMP,
		C.EB_HOOK_BEGIN_IN_COLOR_JPEG,
		C.EB_HOOK_BEGIN_KEYWORD,
		C.EB_HOOK_BEGIN_MONO_GRAPHIC,
		C.EB_HOOK_BEGIN_MPEG,
		C.EB_HOOK_BEGIN_NARROW,
		C.EB_HOOK_BEGIN_NO_NEWLINE,
		C.EB_HOOK_BEGIN_REFERENCE,
		C.EB_HOOK_BEGIN_SUBSCRIPT,
		C.EB_HOOK_BEGIN_SUPERSCRIPT,
		C.EB_HOOK_BEGIN_UNICODE,
		C.EB_HOOK_BEGIN_WAVE,
		C.EB_HOOK_END_CANDIDATE_GROUP,
		C.EB_HOOK_END_CANDIDATE_LEAF,
		C.EB_HOOK_END_CLICKABLE_AREA,
		C.EB_HOOK_END_COLOR_GRAPHIC,
		C.EB_HOOK_END_DECORATION,
		C.EB_HOOK_END_EBXAC_GAIJI,
		C.EB_HOOK_END_EMPHASIS,
		C.EB_HOOK_END_GRAPHIC_REFERENCE,
		C.EB_HOOK_END_GRAY_GRAPHIC,
		C.EB_HOOK_END_IMAGE_PAGE,
		C.EB_HOOK_END_IN_COLOR_GRAPHIC,
		C.EB_HOOK_END_KEYWORD,
		C.EB_HOOK_END_MONO_GRAPHIC,
		C.EB_HOOK_END_MPEG,
		C.EB_HOOK_END_NARROW,
		C.EB_HOOK_END_NO_NEWLINE,
		C.EB_HOOK_END_REFERENCE,
		C.EB_HOOK_END_SUBSCRIPT,
		C.EB_HOOK_END_SUPERSCRIPT,
		C.EB_HOOK_END_UNICODE,
		C.EB_HOOK_END_WAVE,
		C.EB_HOOK_GRAPHIC_REFERENCE,
		C.EB_HOOK_NEWLINE,
		C.EB_HOOK_SET_INDENT,
	}

	for _, hookCode := range hookCodes {
		if errEb := C.installHook(c.hookset, hookCode); errEb != C.EB_SUCCESS {
			return fmt.Errorf("eb_set_hook failed with code %d", errEb)
		}
	}

	return nil
}

func (c *Context) loadInternal(path string) (*Book, error) {
	pathC := C.CString(path)
	defer C.free(unsafe.Pointer(pathC))
	if errEb := C.eb_bind(c.book, pathC); errEb != C.EB_SUCCESS {
		return nil, fmt.Errorf("eb_bind failed with code %d", errEb)
	}

	var (
		book Book
		err  error
	)

	if book.CharCode, err = c.loadCharCode(); err != nil {
		return nil, err
	}

	if book.DiscCode, err = c.loadDiscCode(); err != nil {
		return nil, err
	}

	if book.Subbooks, err = c.loadSubbooks(); err != nil {
		return nil, err
	}

	return &book, nil
}

func (c *Context) loadCharCode() (string, error) {
	var charCode C.EB_Character_Code
	if errEb := C.eb_character_code(c.book, &charCode); errEb != C.EB_SUCCESS {
		return "", fmt.Errorf("eb_character_code failed with code %d", errEb)
	}

	switch charCode {
	case C.EB_CHARCODE_ISO8859_1:
		return "iso8859-1", nil
	case C.EB_CHARCODE_JISX0208:
		return "jisx0208", nil
	case C.EB_CHARCODE_JISX0208_GB2312:
		return "jisx0208/gb2312", nil
	default:
		return "invalid", nil
	}
}

func (c *Context) loadDiscCode() (string, error) {
	var discCode C.EB_Disc_Code
	if errEb := C.eb_disc_type(c.book, &discCode); errEb != C.EB_SUCCESS {
		return "", fmt.Errorf("eb_disc_type failed with code %d", errEb)
	}

	switch discCode {
	case C.EB_DISC_EB:
		return "eb", nil
	case C.EB_DISC_EPWING:
		return "epwing", nil
	default:
		return "invalid", nil
	}
}

func (c *Context) loadSubbooks() ([]BookSubbook, error) {
	var (
		subbookCodes [C.EB_MAX_SUBBOOKS]C.EB_Subbook_Code
		subbookCount C.int
	)

	if errEb := C.eb_subbook_list(c.book, &subbookCodes[0], &subbookCount); errEb != C.EB_SUCCESS {
		return nil, fmt.Errorf("eb_subbook_list failed with code %d", errEb)
	}

	var subbooks []BookSubbook
	for i := 0; i < int(subbookCount); i++ {
		subbook, err := c.loadSubbook(subbookCodes[i])
		if err != nil {
			return nil, err
		}

		subbooks = append(subbooks, *subbook)
	}

	return subbooks, nil
}

func (c *Context) loadSubbook(subbookCode C.EB_Subbook_Code) (*BookSubbook, error) {
	if errEb := C.eb_set_subbook(c.book, subbookCode); errEb != C.EB_SUCCESS {
		return nil, fmt.Errorf("eb_set_subbook failed with code %d", errEb)
	}

	var (
		subbook BookSubbook
		err     error
	)

	if subbook.Title, err = c.loadTitle(); err != nil {
		return nil, err
	}

	if subbook.Copyright, err = c.loadCopyright(); err != nil {
		return nil, err
	}

	blocksSeen := make(map[uint32]bool)

	if errEb := C.eb_search_all_alphabet(c.book); errEb == C.EB_SUCCESS {
		entries, err := c.loadEntries(blocksSeen)
		if err != nil {
			return nil, err
		}

		subbook.Entries = append(subbook.Entries, entries...)
	}

	if errEb := C.eb_search_all_kana(c.book); errEb == C.EB_SUCCESS {
		entries, err := c.loadEntries(blocksSeen)
		if err != nil {
			return nil, err
		}

		subbook.Entries = append(subbook.Entries, entries...)
	}

	if errEb := C.eb_search_all_asis(c.book); errEb == C.EB_SUCCESS {
		entries, err := c.loadEntries(blocksSeen)
		if err != nil {
			return nil, err
		}

		subbook.Entries = append(subbook.Entries, entries...)
	}

	return &subbook, nil
}

func (c *Context) loadEntries(blocksSeen map[uint32]bool) ([]BookEntry, error) {
	var entries []BookEntry

	for {
		var (
			hits     [256]C.EB_Hit
			hitCount C.int
		)

		if errEb := C.eb_hit_list(c.book, (C.int)(len(hits)), &hits[0], &hitCount); errEb != C.EB_SUCCESS {
			return nil, fmt.Errorf("eb_hit_list failed with code %d", errEb)
		}

		for _, hit := range hits[:hitCount] {
			var (
				entry BookEntry
				err   error
			)

			if entry.Heading, err = c.loadContent(hit.heading, blockTypeHeading); err != nil {
				return nil, err
			}

			if entry.Text, err = c.loadContent(hit.text, blockTypeHeading); err != nil {
				return nil, err
			}

			hasher := crc32.NewIEEE()
			hasher.Write([]byte(entry.Heading))
			hasher.Write([]byte(entry.Text))

			sum := hasher.Sum32()
			if seen, _ := blocksSeen[sum]; !seen {
				entries = append(entries, entry)
				blocksSeen[sum] = true
			}
		}

		if hitCount == 0 {
			return entries, nil
		}
	}
}

func (c *Context) loadTitle() (string, error) {
	var data [C.EB_MAX_TITLE_LENGTH + 1]C.char
	if errEb := C.eb_subbook_title(c.book, &data[0]); errEb != C.EB_SUCCESS {
		return "", fmt.Errorf("eb_subbook_title failed with code %d", errEb)
	}

	return c.decoder.String(C.GoString(&data[0]))
}

func (c *Context) loadCopyright() (string, error) {
	if C.eb_have_copyright(c.book) == 0 {
		return "", nil
	}

	var position C.EB_Position
	if errEb := C.eb_copyright(c.book, &position); errEb != C.EB_SUCCESS {
		return "", fmt.Errorf("eb_copyright failed with code %d", errEb)
	}

	return c.loadContent(position, blockTypeText)
}

func (c *Context) loadContent(position C.EB_Position, blockType blockType) (string, error) {
	for {
		var (
			data     = (*C.char)(unsafe.Pointer(&c.buffer[0]))
			dataSize = (C.ulong)(len(c.buffer))
			dataUsed C.long
		)

		if errEb := C.eb_seek_text(c.book, &position); errEb != C.EB_SUCCESS {
			return "", fmt.Errorf("eb_seek_text failed with code %d", errEb)
		}

		switch blockType {
		case blockTypeHeading:
			if errEb := C.eb_read_heading(c.book, nil, c.hookset, nil, dataSize, data, &dataUsed); errEb != C.EB_SUCCESS {
				return "", fmt.Errorf("eb_read_heading failed with code %d", errEb)
			}
		case blockTypeText:
			if errEb := C.eb_read_text(c.book, nil, c.hookset, nil, dataSize, data, &dataUsed); errEb != C.EB_SUCCESS {
				return "", fmt.Errorf("eb_read_text failed with code %d", errEb)
			}
		default:
			panic("invalid block type")
		}

		if dataUsed+8 >= (C.long)(dataSize) {
			c.buffer = make([]byte, dataSize*2)
		} else {
			return c.decoder.String(C.GoString(data))
		}
	}
}

func Load(path string) (*Book, error) {
	var context Context
	if err := context.initialize(); err != nil {
		return nil, err
	}

	defer context.shutdown()
	return context.loadInternal(path)
}