use std::ops::RangeInclusive;
use std::fmt::{ Debug, Formatter, Result as FmtResult };
use num_enum::{ FromPrimitive, IntoPrimitive };
use bytemuck::{ Zeroable, Pod };

use super::ReadError;
use super::core::*;
use super::common::*;

// Encoding Record

#[derive(Clone, Copy, Zeroable, Pod)]
#[repr(transparent)]
pub struct EncodingRecord([u8; 8]);

impl<'a> RandomAccess<'a> for &'a EncodingRecord {
	fn bytes(&self) -> &'a [u8] { &self.0 }
}

impl EncodingRecord {
	pub fn platform(&self) -> Platform { self.uint16(0).into() }
	pub fn encoding(&self) -> PlatformEncoding { (self.platform(), self.uint16(2)).into() }
	pub fn subtable_offset(&self) -> u32 { self.uint32(4) }
}

impl Debug for EncodingRecord {
	fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
		f.debug_struct("EncodingRecord")
			.field("platform", &self.platform())
			.field("encoding", &self.encoding())
			.field("subtable_offset", &self.subtable_offset())
			.finish()
	}
}

// Format

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
#[derive(FromPrimitive, IntoPrimitive)]
#[repr(u16)]
pub enum Format {
	ByteEncodingTable = 0,
	HighByteMappingTable = 2,
	SegmentMappingTable = 4,
	TrimmedMappingTable = 6,

	MixedCoverageTable = 8,
	TrimmedArrayTable = 10,
	SegmentCoverageTable = 12,
	ManyToOneRangeMappingTable = 13,
	UnicodeVariationSequenceTable = 14,

	#[num_enum(catch_all)]
	Unknown(u16),
}

// Byte Encoding Table

#[derive(Clone, Copy)]
pub struct ByteEncodingTable<'a> {
	encoding: PlatformEncoding,
	data: &'a [u8],
}

impl<'a> RandomAccess<'a> for ByteEncodingTable<'a> {
	fn bytes(&self) -> &'a [u8] { self.data }
}

impl<'a> ByteEncodingTable<'a> {
	pub fn format(&self) -> Format { self.uint16(0).into() }
	pub fn length(&self) -> u16 { self.uint16(2) }
	pub fn encoding_and_language(&self) -> PlatformEncodingAndLanguage { (self.encoding, self.uint16(4)).into() }
	pub fn glyph_ids(&self) -> &'a [u8] { self.array(6, self.length() as usize - 6) }

	pub fn map(&self, value: u8) -> Option<u8> {
		let ids = self.glyph_ids();
		let value = value as usize;
		if value < ids.len() {
			Some(ids[value])
		} else {
			None
		}
	}
}

impl<'a> Debug for ByteEncodingTable<'a> {
	fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
		f.debug_struct("ByteEncodingTable")
			.field("encoding_and_language", &self.encoding_and_language())
			.field("glyph_ids", &self.glyph_ids())
			.finish()
	}
}

// Segment Mapping Table

#[derive(Clone, Copy)]
pub struct ContinuousSegment {
	end_code: u16,
	start_code: u16,
	id_delta: i16,
}

impl ContinuousSegment {
	pub fn chars(&self) -> RangeInclusive<u16> { self.start_code..=self.end_code }
	pub fn contains(&self, c: u16) -> bool { c >= self.start_code && c <= self.end_code }

	pub fn glyphs(&self) -> RangeInclusive<u16> {
		let start = self.start_code as i32 + self.id_delta as i32;
		let stop = self.end_code as i32 + self.id_delta as i32;
		(start as u16)..=(stop as u16)
	}

	pub fn map(&self, c: u16) -> u16 {
		if !self.contains(c) { return 0; }
		let value = c as i32 + self.id_delta as i32;
		value as u16
	}
}

impl Debug for ContinuousSegment {
	fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
		f.debug_struct("ContinuousSegment")
			.field("chars", &self.chars())
			.field("glyphs", &self.glyphs())
			.finish()
	}
}

#[derive(Clone, Copy)]
pub struct GlyphDeltaMapping<'a> {
	glyph_ids: U16Array<'a>,
	id_delta: i16,
}

impl<'a> GlyphDeltaMapping<'a> {
	pub fn len(&self) -> usize { self.glyph_ids.len() }
	pub fn is_empty(&self) -> bool { self.len() == 0 }
	pub fn get(&self, index: usize) -> u16 {
		let glyph_id = self.glyph_ids.get(index);
		if glyph_id == 0 { return 0; }
		let value = glyph_id as i32 + self.id_delta as i32;
		value as u16
	}
	pub fn iter(&self) -> impl ExactSizeIterator<Item = u16> + '_ {
		self.glyph_ids.iter().map(|x| match x {
			0 => 0,
			x => (x as i32 + self.id_delta as i32) as u16,
		})
	}
}

impl<'a> Debug for GlyphDeltaMapping<'a> {
	fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
		f.debug_list()
			.entries(self.iter())
			.finish()
	}
}

#[derive(Clone, Copy)]
pub struct TableSegment<'a> {
	end_code: u16,
	start_code: u16,
	glyphs: GlyphDeltaMapping<'a>,
}

impl<'a> TableSegment<'a> {
	pub fn chars(&self) -> RangeInclusive<u16> { self.start_code..=self.end_code }
	pub fn contains(&self, c: u16) -> bool { c >= self.start_code && c <= self.end_code }
	pub fn glyphs(&self) -> GlyphDeltaMapping<'a> { self.glyphs }

	pub fn map(&self, c: u16) -> u16 {
		if !self.contains(c) { return 0; }
		let index = (c - self.start_code) as usize;
		self.glyphs.get(index)
	}
}

impl<'a> Debug for TableSegment<'a> {
	fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
		f.debug_struct("TableSegment")
			.field("chars", &self.chars())
			.field("glyphs", &self.glyphs())
			.finish()
	}
}

#[derive(Clone, Copy)]
pub enum Segment<'a> {
	Continuous(ContinuousSegment),
	Table(TableSegment<'a>),
}

impl<'a> Segment<'a> {
	pub fn chars(&self) -> RangeInclusive<u16> {
		match self {
			Self::Continuous(x) => x.chars(),
			Self::Table(x) => x.chars(),
		}
	}

	pub fn contains(&self, c: u16) -> bool {
		match self {
			Self::Continuous(x) => x.contains(c),
			Self::Table(x) => x.contains(c),
		}
	}

	pub fn map(&self, c: u16) -> u16 {
		match self {
			Self::Continuous(x) => x.map(c),
			Self::Table(x) => x.map(c),
		}
	}
}

impl<'a> Debug for Segment<'a> {
	fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
		match self {
			Self::Continuous(x) => x.fmt(f),
			Self::Table(x) => x.fmt(f),
		}
	}
}

#[derive(Clone)]
pub struct Segments<'a> {
	table: SegmentMappingTable<'a>,
	index: u16,
}

impl<'a> Iterator for Segments<'a> {
	type Item = Segment<'a>;
	fn next(&mut self) -> Option<Self::Item> {
		if self.index < self.table.segment_count() {
			let segment = self.table.segment(self.index);
			self.index += 1;
			Some(segment)
		} else { None }
	}
	fn size_hint(&self) -> (usize, Option<usize>) {
		let len = self.table.length() as usize;
		(len, Some(len))
	}
}

impl<'a> ExactSizeIterator for Segments<'a> {}

impl<'a> Debug for Segments<'a> {
	fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
		f.debug_list()
			.entries(self.clone())
			.finish()
	}
}

#[derive(Clone, Copy)]
pub struct SegmentMappingTable<'a> {
	encoding: PlatformEncoding,
	data: &'a [u8],
}

impl<'a> RandomAccess<'a> for SegmentMappingTable<'a> {
	fn bytes(&self) -> &'a [u8] { self.data }
}

impl<'a> SegmentMappingTable<'a> {
	pub fn format(&self) -> Format { self.uint16(0).into() }
	pub fn length(&self) -> u16 { self.uint16(2) }
	pub fn encoding_and_language(&self) -> PlatformEncodingAndLanguage { (self.encoding, self.uint16(4)).into() }
	pub fn segment_count_x2(&self) -> u16 { self.uint16(6) }
	pub fn segment_count(&self) -> u16 { self.segment_count_x2() >> 1 }
	pub fn search_range(&self) -> u16 { self.uint16(8) }
	pub fn entry_selector(&self) -> u16 { self.uint16(10) }
	pub fn range_shift(&self) -> u16 { self.uint16(12) }
	pub fn end_codes(&self) -> U16Array<'a> { self.uint16_array(14, self.segment_count() as usize) }
	pub fn segment(&self, index: u16) -> Segment<'a> {
		let size = self.segment_count_x2() as usize;
		let offset = 14 + ((index as usize) << 1);
		let end_code = self.uint16(offset);
		let offset = offset + 2 + size;
		let start_code = self.uint16(offset);
		let offset = offset + size;
		let id_delta = self.int16(offset);
		let offset = offset + size;
		let id_range_offset = self.uint16(offset);
		if id_range_offset == 0 {
			Segment::Continuous(ContinuousSegment {
				end_code,
				start_code,
				id_delta,
			})
		} else {
			let offset = offset + id_range_offset as usize;
			let count  = (end_code - start_code + 1) as usize;
			let glyph_ids = self.uint16_array(offset, count);
			Segment::Table(TableSegment {
				end_code,
				start_code,
				glyphs: GlyphDeltaMapping {
					glyph_ids,
					id_delta,
				},
			})
		}
	}
	pub fn segments(&self) -> Segments<'a> {
		Segments { table: *self, index: 0 }
	}
	pub fn segment_of(&self, value: u16) -> Option<Segment<'a>> {
		// TODO binary search
		for (i, stop) in self.end_codes().iter().enumerate() {
			if value <= stop {
				let seg = self.segment(i as u16);
				return if seg.contains(value) { Some(seg) } else { None };
			}
		}
		None
	}
	pub fn map(&self, value: u16) -> u16 {
		self.segment_of(value).map(|x| x.map(value)).unwrap_or_default()
	}
}

impl<'a> Debug for SegmentMappingTable<'a> {
	fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
		f.debug_struct("SegmentMappingTable")
			.field("encoding_and_language", &self.encoding_and_language())
			.field("segments", &self.segments())
			.finish()
	}
}

// Trimmed Mapping Table

#[derive(Clone, Copy)]
pub struct TrimmedMappingTable<'a> {
	encoding: PlatformEncoding,
	data: &'a [u8],
}

impl<'a> RandomAccess<'a> for TrimmedMappingTable<'a> {
	fn bytes(&self) -> &'a [u8] { self.data }
}

impl<'a> TrimmedMappingTable<'a> {
	pub fn format(&self) -> Format { self.uint16(0).into() }
	pub fn length(&self) -> u16 { self.uint16(2) }
	pub fn encoding_and_language(&self) -> PlatformEncodingAndLanguage { (self.encoding, self.uint16(4)).into() }
	pub fn first_code(&self) -> u16 { self.uint16(6) }
	pub fn entry_count(&self) -> u16 { self.uint16(8) }
	pub fn glyph_ids(&self) -> U16Array<'a> { self.uint16_array(10, self.entry_count() as usize) }

	// TODO
}

impl<'a> Debug for TrimmedMappingTable<'a> {
	fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
		f.debug_struct("TrimmedMappingTable")
			.field("encoding_and_language", &self.encoding_and_language())
			.field("first_code", &self.first_code())
			.field("glyph_ids", &self.glyph_ids())
			.finish()
	}
}

// Segment Coverage Table

#[derive(Clone, Copy, Zeroable, Pod)]
#[repr(transparent)]
pub struct SequentialMapGroup([u8; 12]);

impl<'a> RandomAccess<'a> for &'a SequentialMapGroup {
	fn bytes(&self) -> &'a [u8] { &self.0 }
}

impl SequentialMapGroup {
	pub fn start_char(&self) -> u32 { self.uint32(0) }
	pub fn end_char(&self) -> u32 { self.uint32(4) }
	pub fn start_glyph(&self) -> u32 { self.uint32(8) }

	pub fn chars(&self) -> RangeInclusive<u32> {
		self.start_char()..=self.end_char()
	}

	pub fn glyphs(&self) -> RangeInclusive<u32> {
		let chars = self.chars();
		let start = self.start_glyph();
		let stop = start + chars.end() - chars.start();
		start..=stop
	}

	pub fn contains(&self, c: u32) -> bool {
		let chars = self.chars();
		c >= *chars.start() && c <= *chars.end()
	}

	pub fn map(&self, c: u32) -> u32 {
		let chars = self.chars();
		if c >= *chars.start() && c <= *chars.end() {
			self.start_glyph() + c - *chars.start()
		} else { 0 }
	}
}

impl Debug for SequentialMapGroup {
	fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
		f.debug_struct("SequentialMapGroup")
			.field("chars", &self.chars())
			.field("glyphs", &self.glyphs())
			.finish()
	}
}

#[derive(Clone, Copy)]
pub struct SegmentCoverageTable<'a> {
	encoding: PlatformEncoding,
	data: &'a [u8],
}

impl<'a> RandomAccess<'a> for SegmentCoverageTable<'a> {
	fn bytes(&self) -> &'a [u8] { self.data }
}

impl<'a> SegmentCoverageTable<'a> {
	pub fn format(&self) -> Format { self.uint16(0).into() }
	pub fn length(&self) -> u32 { self.uint32(4) }
	pub fn encoding_and_language(&self) -> PlatformEncodingAndLanguage { (self.encoding, self.uint32(8) as u16).into() } // TODO check if upper bits have a meaning
	pub fn groups(&self) -> &'a [SequentialMapGroup] { self.array(16, self.uint32(12) as usize) }

	pub fn group_of(&self, value: u32) -> Option<&'a SequentialMapGroup> {
		// TODO binary search
		for group in self.groups() {
			if value <= group.end_char() {
				return if value >= group.start_char() { Some(group) } else { None };
			}
		}
		None
	}

	pub fn map(&self, value: u32) -> u32 {
		self.group_of(value).map(|x| x.map(value)).unwrap_or_default()
	}
}

impl<'a> Debug for SegmentCoverageTable<'a> {
	fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
		f.debug_struct("SegmentCoverageTable")
			.field("encoding_and_language", &self.encoding_and_language())
			.field("groups", &self.groups())
			.finish()
	}
}

// Generic Subtable

#[derive(Clone, Copy)]
pub enum Subtable<'a> {
	ByteEncodingTable(ByteEncodingTable<'a>),
	SegmentMappingTable(SegmentMappingTable<'a>),
	TrimmedMappingTable(TrimmedMappingTable<'a>),
	SegmentCoverageTable(SegmentCoverageTable<'a>),
}

impl<'a> RandomAccess<'a> for Subtable<'a> {
	fn bytes(&self) -> &'a [u8] {
		match self {
			Self::ByteEncodingTable(x) => x.bytes(),
			Self::SegmentMappingTable(x) => x.bytes(),
			Self::TrimmedMappingTable(x) => x.bytes(),
			Self::SegmentCoverageTable(x) => x.bytes(),
		}
	}
}

impl<'a> Subtable<'a> {
	pub fn format(&self) -> Format { self.uint16(0).into() }

	pub fn encoding_and_language(&self) -> PlatformEncodingAndLanguage {
		match self {
			Self::ByteEncodingTable(x) => x.encoding_and_language(),
			Self::SegmentMappingTable(x) => x.encoding_and_language(),
			Self::TrimmedMappingTable(x) => x.encoding_and_language(),
			Self::SegmentCoverageTable(x) => x.encoding_and_language(),
		}
	}
}

impl<'a> Debug for Subtable<'a> {
	fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
		match self {
			Self::ByteEncodingTable(x) => x.fmt(f),
			Self::SegmentMappingTable(x) => x.fmt(f),
			Self::TrimmedMappingTable(x) => x.fmt(f),
			Self::SegmentCoverageTable(x) => x.fmt(f),
		}
	}
}

impl<'a> Subtable<'a> {
	pub fn try_from(data: &'a [u8], encoding: PlatformEncoding) -> Result<Self, ReadError> {
		if data.len() < 6 {
			return Err(ReadError::UnexpectedEof);
		}

		let format: Format = data.uint16(0).into();
		match format {
			Format::ByteEncodingTable => {
				let length = data.uint16(2);
				let data = &data[0..length as usize];
				Ok(Self::ByteEncodingTable(ByteEncodingTable { encoding, data }))
			},
			Format::SegmentMappingTable => {
				let length = data.uint16(2);
				let data = &data[0..length as usize];
				Ok(Self::SegmentMappingTable(SegmentMappingTable { encoding, data }))
			},
			Format::TrimmedMappingTable => {
				let length = data.uint16(2);
				let data = &data[0..length as usize];
				Ok(Self::TrimmedMappingTable(TrimmedMappingTable { encoding, data }))
			},
			Format::SegmentCoverageTable => {
				let length = data.uint32(4);
				let data = &data[0..length as usize];
				Ok(Self::SegmentCoverageTable(SegmentCoverageTable { encoding, data }))
			},
			Format::Unknown(x) => Err(ReadError::UnknownCmapFormat(x)),
			x => Err(ReadError::UnsupportedCmapFormat(x)),
		}
	}
}

// Character To Glyph Map

#[derive(Clone, Copy)]
#[repr(transparent)]
pub struct CharacterToGlyphMap<'a>(&'a [u8]);

impl<'a> RandomAccess<'a> for CharacterToGlyphMap<'a> {
	fn bytes(&self) -> &'a [u8] { self.0 }
}

impl<'a> CharacterToGlyphMap<'a> {
	pub fn version(&self) -> u16 { self.uint16(0) }
	pub fn subtable_count(&self) -> u16 { self.uint16(2) }
	pub fn encoding_records(&self) -> &'a [EncodingRecord] { self.array(4, self.subtable_count() as usize) }

	pub fn subtable(&self, record: &EncodingRecord) -> Result<Subtable<'a>, ReadError> {
		Subtable::try_from(&self.0[record.subtable_offset() as usize..], record.encoding())
	}

	pub fn subtables(&self) -> impl ExactSizeIterator<Item = Result<Subtable<'a>, ReadError>> + '_ {
		self.encoding_records().iter().map(|x| self.subtable(x))
	}
}

impl<'a> Debug for CharacterToGlyphMap<'a> {
	fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
		f.debug_list()
			.entries(self.subtables())
			.finish()
	}
}

impl<'a> TryFrom<&'a [u8]> for CharacterToGlyphMap<'a> {
	type Error = ReadError;
	fn try_from(value: &'a [u8]) -> Result<Self, Self::Error> {
		if value.len() < 4 {
			return Err(ReadError::UnexpectedEof);
		}

		let value = CharacterToGlyphMap(value);

		let version = value.version();
		if version != 0 {
			return Err(ReadError::UnsupportedTableVersionSingle(version));
		}

		if value.bytes().len() < 4 + value.subtable_count() as usize * 8 {
			return Err(ReadError::UnexpectedEof);
		}

		Ok(value)
	}
}