"""
PNG picture file parser.

Documents:
- RFC 2083
  http://www.faqs.org/rfcs/rfc2083.html

Author: Victor Stinner
"""

from hachoir.parser import Parser
from hachoir.field import (FieldSet, Fragment,
                           ParserError, MissingField,
                           UInt8, UInt16, UInt32,
                           String, CString,
                           Bytes, RawBytes,
                           Bit, NullBits,
                           Enum, CompressedField)
from hachoir.parser.image.common import RGB
from hachoir.core.text_handler import textHandler, hexadecimal
from hachoir.core.endian import NETWORK_ENDIAN
from hachoir.core.tools import humanFilesize
from datetime import datetime

MAX_FILESIZE = 500 * 1024 * 1024  # 500 MB

try:
    from zlib import decompressobj


    class Gunzip:
        def __init__(self, stream):
            self.gzip = decompressobj()

        def __call__(self, size, data=None):
            if data is None:
                data = self.gzip.unconsumed_tail
            return self.gzip.decompress(data, size)


    has_deflate = True
except ImportError:
    has_deflate = False

UNIT_NAME = {1: "Meter"}
COMPRESSION_NAME = {
    0: u"deflate"  # with 32K sliding window
}
MAX_CHUNK_SIZE = 5 * 1024 * 1024  # Maximum chunk size (5 MB)


def headerParse(parent):
    yield UInt32(parent, "width", "Width (pixels)")
    yield UInt32(parent, "height", "Height (pixels)")
    yield UInt8(parent, "bit_depth", "Bit depth")
    yield NullBits(parent, "reserved", 5)
    yield Bit(parent, "has_alpha", "Has alpha channel?")
    yield Bit(parent, "color", "Color used?")
    yield Bit(parent, "has_palette", "Has a color palette?")
    yield Enum(UInt8(parent, "compression", "Compression method"), COMPRESSION_NAME)
    yield UInt8(parent, "filter", "Filter method")
    yield UInt8(parent, "interlace", "Interlace method")


def headerDescription(parent):
    return "Header: %ux%u pixels and %u bits/pixel" % \
           (parent["width"].value, parent["height"].value, getBitsPerPixel(parent))


def paletteParse(parent):
    size = parent["size"].value
    if (size % 3) != 0:
        raise ParserError("Palette have invalid size (%s), should be 3*n!" % size)
    nb_colors = size // 3
    for index in xrange(nb_colors):
        yield RGB(parent, "color[]")


def paletteDescription(parent):
    return "Palette: %u colors" % (parent["size"].value // 3)


def gammaParse(parent):
    yield UInt32(parent, "gamma", "Gamma (x100,000)")


def gammaValue(parent):
    return float(parent["gamma"].value) / 100000


def gammaDescription(parent):
    return "Gamma: %.3f" % parent.value


def textParse(parent):
    yield CString(parent, "keyword", "Keyword", charset="ISO-8859-1")
    length = parent["size"].value - parent["keyword"].size // 8
    if length:
        yield String(parent, "text", length, "Text", charset="ISO-8859-1")


def textDescription(parent):
    if "text" in parent:
        return u'Text: %s' % parent["text"].display
    else:
        return u'Text'


def timestampParse(parent):
    yield UInt16(parent, "year", "Year")
    yield UInt8(parent, "month", "Month")
    yield UInt8(parent, "day", "Day")
    yield UInt8(parent, "hour", "Hour")
    yield UInt8(parent, "minute", "Minute")
    yield UInt8(parent, "second", "Second")


def timestampValue(parent):
    value = datetime(
        parent["year"].value, parent["month"].value, parent["day"].value,
        parent["hour"].value, parent["minute"].value, parent["second"].value)
    return value


def physicalParse(parent):
    yield UInt32(parent, "pixel_per_unit_x", "Pixel per unit, X axis")
    yield UInt32(parent, "pixel_per_unit_y", "Pixel per unit, Y axis")
    yield Enum(UInt8(parent, "unit", "Unit type"), UNIT_NAME)


def physicalDescription(parent):
    x = parent["pixel_per_unit_x"].value
    y = parent["pixel_per_unit_y"].value
    desc = "Physical: %ux%u pixels" % (x, y)
    if parent["unit"].value == 1:
        desc += " per meter"
    return desc


def parseBackgroundColor(parent):
    yield UInt16(parent, "red")
    yield UInt16(parent, "green")
    yield UInt16(parent, "blue")


def backgroundColorDesc(parent):
    rgb = parent["red"].value, parent["green"].value, parent["blue"].value
    name = RGB.color_name.get(rgb)
    if not name:
        name = "#%02X%02X%02X" % rgb
    return "Background color: %s" % name


class ImageData(Fragment):
    def __init__(self, parent, name="compressed_data"):
        Fragment.__init__(self, parent, name, None, 8 * parent["size"].value)
        data = parent.name.split('[')
        data, next = "../%s[%%u]" % data[0], int(data[1][:-1]) + 1
        first = parent.getField(data % 0)
        if first is parent:
            first = None
            if has_deflate:
                CompressedField(self, Gunzip)
        else:
            first = first[name]
        try:
            _next = parent[data % next]
            next = lambda: _next[name]
        except MissingField:
            next = None
        self.setLinks(first, next)


def parseTransparency(parent):
    for i in range(parent["size"].value):
        yield UInt8(parent, "alpha_value[]", "Alpha value for palette entry %i" % i)


def getBitsPerPixel(header):
    nr_component = 1
    if header["has_alpha"].value:
        nr_component += 1
    if header["color"].value and not header["has_palette"].value:
        nr_component += 2
    return nr_component * header["bit_depth"].value


class Chunk(FieldSet):
    TAG_INFO = {
        "tIME": ("time", timestampParse, "Timestamp", timestampValue),
        "pHYs": ("physical", physicalParse, physicalDescription, None),
        "IHDR": ("header", headerParse, headerDescription, None),
        "PLTE": ("palette", paletteParse, paletteDescription, None),
        "gAMA": ("gamma", gammaParse, gammaDescription, gammaValue),
        "tEXt": ("text[]", textParse, textDescription, None),
        "tRNS": ("transparency", parseTransparency, "Transparency Info", None),

        "bKGD": ("background", parseBackgroundColor, backgroundColorDesc, None),
        "IDAT": ("data[]", lambda parent: (ImageData(parent),), "Image data", None),
        "iTXt": ("utf8_text[]", None, "International text (encoded in UTF-8)", None),
        "zTXt": ("comp_text[]", None, "Compressed text", None),
        "IEND": ("end", None, "End", None)
    }

    def createValueFunc(self):
        return self.value_func(self)

    def __init__(self, parent, name, description=None):
        FieldSet.__init__(self, parent, name, description)
        self._size = (self["size"].value + 3 * 4) * 8
        if MAX_CHUNK_SIZE < (self._size // 8):
            raise ParserError("PNG: Chunk is too big (%s)"
                              % humanFilesize(self._size // 8))
        tag = self["tag"].value
        self.desc_func = None
        self.value_func = None
        if tag in self.TAG_INFO:
            self._name, self.parse_func, desc, value_func = self.TAG_INFO[tag]
            if value_func:
                self.value_func = value_func
                self.createValue = self.createValueFunc
            if desc:
                if isinstance(desc, str):
                    self._description = desc
                else:
                    self.desc_func = desc
        else:
            self._description = ""
            self.parse_func = None

    def createFields(self):
        yield UInt32(self, "size", "Size")
        yield String(self, "tag", 4, "Tag", charset="ASCII")

        size = self["size"].value
        if size != 0:
            if self.parse_func:
                for field in self.parse_func(self):
                    yield field
            else:
                yield RawBytes(self, "content", size, "Data")
        yield textHandler(UInt32(self, "crc32", "CRC32"), hexadecimal)

    def createDescription(self):
        if self.desc_func:
            return self.desc_func(self)
        else:
            return "Chunk: %s" % self["tag"].display


class PngFile(Parser):
    PARSER_TAGS = {
        "id": "png",
        "category": "image",
        "file_ext": ("png",),
        "mime": (u"image/png", u"image/x-png"),
        "min_size": 8 * 8,  # just the identifier
        "magic": [('\x89PNG\r\n\x1A\n', 0)],
        "description": "Portable Network Graphics (PNG) picture"
    }
    endian = NETWORK_ENDIAN

    def validate(self):
        if self["id"].value != '\x89PNG\r\n\x1A\n':
            return "Invalid signature"
        if self[1].name != "header":
            return "First chunk is not header"
        return True

    def createFields(self):
        yield Bytes(self, "id", 8, r"PNG identifier ('\x89PNG\r\n\x1A\n')")
        while not self.eof:
            yield Chunk(self, "chunk[]")

    def createDescription(self):
        header = self["header"]
        desc = "PNG picture: %ux%ux%u" % (
            header["width"].value, header["height"].value, getBitsPerPixel(header))
        if header["has_alpha"].value:
            desc += " (alpha layer)"
        return desc

    def createContentSize(self):
        field = self["header"]
        start = field.absolute_address + field.size
        end = MAX_FILESIZE * 8
        pos = self.stream.searchBytes("\0\0\0\0IEND\xae\x42\x60\x82", start, end)
        if pos is not None:
            return pos + 12 * 8
        return None