use std::cmp::Reverse;
use std::collections::{HashMap, HashSet};
use std::convert::TryFrom;
use std::fmt;
use std::fs::File;
use std::io::{BufRead, BufReader, Read, Seek, SeekFrom};
use std::path::{Path, PathBuf};
use std::rc::Rc;

use clang::{Entity, EntityKind, EntityVisitResult};

use crate::class::ClassKind;
use crate::type_ref::CppNameStyle;
use crate::{
	is_opencv_path, opencv_module_from_path, settings, Class, Element, EntityWalkerExt, EntityWalkerVisitor, MemoizeMap,
	MemoizeMapExt, NamePool, WalkAction,
};

#[derive(Copy, Clone, Debug)]
pub enum ClassKindOverride {
	Boxed,
	Simple,
	BoxedForced,
	System,
}

impl ClassKindOverride {
	pub fn is_boxed(self) -> bool {
		match self {
			ClassKindOverride::Boxed | ClassKindOverride::BoxedForced => true,
			ClassKindOverride::Simple | ClassKindOverride::System => false,
		}
	}
}

#[derive(Clone, Debug)]
pub struct ExportConfig {
	pub class_kind_override: ClassKindOverride,
	pub deprecated: bool,
	pub no_return: bool,
	pub no_except: bool,
	pub no_discard: bool,
	// the function is used to generate only the helper types using OCVRS_ONLY_DEPENDENT_TYPES
	pub only_generated_types: bool,
}

impl Default for ExportConfig {
	fn default() -> Self {
		Self {
			class_kind_override: ClassKindOverride::Boxed,
			deprecated: false,
			no_return: false,
			no_except: false,
			no_discard: false,
			only_generated_types: false,
		}
	}
}

impl ExportConfig {
	/// Doesn't change export config, but putting it into `ELEMENT_EXPORT_TWEAK` will force the creation of the default `ExportConfig`
	pub fn export(src: ExportConfig) -> Option<ExportConfig> {
		Some(src)
	}

	pub fn no_export(_src: ExportConfig) -> Option<ExportConfig> {
		None
	}

	pub fn override_boxed(mut src: ExportConfig) -> Option<ExportConfig> {
		src.class_kind_override = ClassKindOverride::Boxed;
		Some(src)
	}

	pub fn force_boxed(mut src: ExportConfig) -> Option<ExportConfig> {
		src.class_kind_override = ClassKindOverride::BoxedForced;
		Some(src)
	}

	pub fn simple(mut src: ExportConfig) -> Option<ExportConfig> {
		src.class_kind_override = ClassKindOverride::Simple;
		Some(src)
	}

	pub fn system(mut src: ExportConfig) -> Option<ExportConfig> {
		src.class_kind_override = ClassKindOverride::System;
		Some(src)
	}
}

pub struct RenameConfig {
	pub rename: Rc<str>,
}

#[derive(Eq, PartialEq, Hash)]
struct ExportIdx {
	path: PathBuf,
	line: u32,
	line_offset: usize,
}

/// Populates different fields of [GeneratorEnv] to be used later for binding generation.
///
/// This is 1st pass of the analysis. It performs the collection of the necessary auxiliary data like which descendants a class has.
struct GeneratorEnvPopulator<'tu, 'ge> {
	gen_env: &'ge mut GeneratorEnv<'tu>,
}

impl<'tu> GeneratorEnvPopulator<'tu, '_> {
	fn add_func_comment(&mut self, entity: Entity) {
		let raw_comment = entity.doc_comment();
		// Note to future: str::contains is very fast, no sense in trying to avoid going over string multiple times
		if !raw_comment.is_empty() && !raw_comment.contains("@overload") && !raw_comment.contains("@copybrief") {
			let name = entity.cpp_name(CppNameStyle::Reference).into_owned();
			let line = entity.get_location().map_or(0, |l| l.get_file_location().line);
			let defs = self.gen_env.func_comments.entry(name).or_default();
			defs.push((line, raw_comment.into_owned()));
			// reverse sort due to how we're querying this; the amount of elements in this Vec doesn't go above 7
			defs.sort_unstable_by_key(|(line, _)| Reverse(*line));
		}
	}

	fn add_descendant(&mut self, base_class: Entity, descendant: Entity<'tu>) {
		self
			.gen_env
			.descendants
			.entry(base_class.cpp_name(CppNameStyle::Reference).into_owned())
			.or_insert_with(|| HashSet::with_capacity(4))
			.insert(descendant);
	}
}

impl<'tu> EntityWalkerVisitor<'tu> for GeneratorEnvPopulator<'tu, '_> {
	fn wants_file(&mut self, path: &Path) -> bool {
		is_opencv_path(path) || opencv_module_from_path(path).map_or(false, |m| m == self.gen_env.module())
	}

	fn visit_entity(&mut self, entity: Entity<'tu>) -> WalkAction {
		match entity.get_kind() {
			EntityKind::ClassDecl | EntityKind::StructDecl => {
				entity.visit_children(|child, _| {
					match child.get_kind() {
						EntityKind::BaseSpecifier => {
							self.add_descendant(child.get_definition().expect("Can't get base class definition"), entity);
						}
						EntityKind::Constructor
						| EntityKind::Method
						| EntityKind::FunctionTemplate
						| EntityKind::ConversionFunction => {
							self.add_func_comment(child);
						}
						_ => {}
					}
					EntityVisitResult::Continue
				});
			}
			EntityKind::FunctionDecl => {
				self.add_func_comment(entity);
			}
			_ => {}
		}
		WalkAction::Continue
	}
}

/// Generator environment or context, contains a global data (passed by immutable reference) for the binding generation
///
/// This is partially pre-populated in an additional pass before the generation to provide some necessary data that's not available
/// at the generation moment. E.g. list of descendants of a particular class.
pub struct GeneratorEnv<'tu> {
	/// The name of the module that's currently being generated
	module: &'tu str,
	export_map: HashMap<ExportIdx, ExportConfig>,
	rename_map: HashMap<ExportIdx, RenameConfig>,
	pub func_names: NamePool,
	/// Collection of function comments to be able to replace `@overload` and `@copybrief` comment markers
	func_comments: HashMap<String, Vec<(u32, String)>>,
	/// Cache of the calculated [ClassKind]s
	class_kind_cache: MemoizeMap<String, Option<ClassKind>>,
	descendants: HashMap<String, HashSet<Entity<'tu>>>,
}

impl<'tu> GeneratorEnv<'tu> {
	pub fn new(root_entity: Entity<'tu>, module: &'tu str) -> Self {
		let mut out = Self {
			module,
			export_map: HashMap::with_capacity(1024),
			rename_map: HashMap::with_capacity(64),
			func_names: NamePool::with_capacity(512),
			func_comments: HashMap::with_capacity(2048),
			class_kind_cache: MemoizeMap::new(HashMap::with_capacity(32)),
			descendants: HashMap::with_capacity(16),
		};
		root_entity.walk_opencv_entities(GeneratorEnvPopulator { gen_env: &mut out });
		out
	}

	/// The name of the module that's currently being generated
	pub fn module(&self) -> &str {
		self.module
	}

	fn key(entity: Entity) -> ExportIdx {
		let (loc, line_offset) = if entity.get_kind() == EntityKind::MacroExpansion {
			// sometimes CV_EXPORT macros are located on a separate line so for those we compensate the offset
			let l = entity
				.get_range()
				.expect("Can't get exported macro range")
				.get_end()
				.get_spelling_location();
			let path = l.file.expect("Can't get exported macro file").get_path();
			let mut f = BufReader::new(File::open(path).expect("Can't open export macro file"));
			f.seek(SeekFrom::Start(u64::from(l.offset)))
				.expect("Can't seek export macro file");
			let mut line_offset = 0;
			let mut line = String::with_capacity(8);
			while f.read_line(&mut line).is_ok() {
				if line.trim().is_empty() {
					line_offset += 1;
				} else {
					break;
				}
			}
			if line_offset > 1 {
				panic!("Line offset more than 1 is not supported, modify fuzzy_key in get_export_config() to support higher values");
			}
			(l, line_offset)
		} else {
			let loc = entity
				.get_range()
				.map_or_else(
					// for some reason Apple libclang on macos has problems with get_range() on FacemarkLBF::Params::pupils
					// see https://github.com/twistedfall/opencv-rust/issues/159#issuecomment-668234058
					|| entity.get_location().expect("Can't get entity location"),
					|range| range.get_start(),
				)
				.get_spelling_location();
			(loc, 0)
		};
		ExportIdx {
			path: loc.file.expect("Can't get exported entry file").get_path(),
			line: loc.line,
			line_offset,
		}
	}

	pub fn make_export_config(&mut self, entity: Entity) -> &mut ExportConfig {
		let key = Self::key(entity);
		self.export_map.entry(key).or_default()
	}

	#[inline]
	fn get_with_fuzzy_key<T>(entity: Entity, getter: impl Fn(&ExportIdx) -> Option<T>) -> Option<T> {
		let key = Self::key(entity);
		getter(&key).or_else(|| {
			// for cases where CV_EXPORTS is on the separate line but entity.get_range() spans into it
			let fuzzy_key = ExportIdx { line_offset: 1, ..key };
			getter(&fuzzy_key).or_else(|| {
				if fuzzy_key.line >= 1 {
					// for cases where CV_EXPORTS is on the separate line but entity.get_range() starts on the next line
					let fuzzy_key = ExportIdx {
						line: fuzzy_key.line - 1,
						..fuzzy_key
					};
					getter(&fuzzy_key)
				} else {
					None
				}
			})
		})
	}

	pub fn get_export_config(&self, entity: Entity) -> Option<ExportConfig> {
		let out = Self::get_with_fuzzy_key(entity, |key| self.export_map.get(key)).cloned();
		let cpp_refname = entity.cpp_name(CppNameStyle::Reference);
		if let Some(tweak) = settings::ELEMENT_EXPORT_TWEAK.get(cpp_refname.as_ref()) {
			tweak(out.unwrap_or_default())
		} else {
			out
		}
	}

	pub fn make_rename_config(&mut self, entity: Entity) -> &mut RenameConfig {
		let key = Self::key(entity);
		self
			.rename_map
			.entry(key)
			.or_insert_with(|| RenameConfig { rename: Rc::from("") })
	}

	pub fn get_rename_config(&self, entity: Entity) -> Option<&RenameConfig> {
		Self::get_with_fuzzy_key(entity, |key| self.rename_map.get(key))
	}

	pub fn get_func_comment(&self, line: u32, cpp_refname: &str) -> Option<&str> {
		self
			.func_comments
			.get(cpp_refname)
			.and_then(|comments| {
				comments.iter()
				// try to find the source function comment that is closest to the requested
				.find(|(source_line, _)| *source_line <= line)
				// if it fails return at least something
				.or_else(|| comments.last())
			})
			.map(|(_, comment)| comment.as_str())
	}

	/// Calculates the [ClassKind] of the class `entity` based on the macros connected to its declaration and whether it can be
	/// expressed as simple in Rust
	pub fn get_class_kind(&self, entity: Entity<'tu>) -> Option<ClassKind> {
		let id = entity.cpp_name(CppNameStyle::Reference);
		self.class_kind_cache.memo_get(id.as_ref(), || {
			let entity = entity.get_template().unwrap_or(entity);
			if let Some(range) = entity.get_range() {
				let name_ranges = entity.get_name_ranges();
				if !name_ranges.is_empty() {
					let file_location = range.get_start().get_file_location();
					if let Some(file) = file_location.file {
						let start = u64::from(file_location.offset);
						let end = u64::from(name_ranges[0].get_start().get_file_location().offset);
						let len = usize::try_from(end - start).expect("Buffer length doesn't fit usize");
						let mut buf = vec![0; len];
						if let Ok(mut f) = File::open(file.get_path()) {
							f.seek(SeekFrom::Start(start)).expect("Can't seek");
							f.read_exact(buf.as_mut_slice()).expect("Can't read");
						}
						let export_decl = String::from_utf8(buf).expect("Not a valid UTF-8");
						if export_decl.contains("CV_EXPORTS_W_SIMPLE") || export_decl.contains("CV_EXPORTS_W_MAP") {
							return Some(ClassKind::Simple);
						} else if export_decl.contains("CV_EXPORTS") || export_decl.contains("GAPI_EXPORTS") {
							return Some(ClassKind::Boxed);
						}
					}
				}
			}
			let cls = Class::new(entity, self);
			if cls.can_be_simple() {
				return Some(ClassKind::Simple);
			}
			None
		})
	}

	/// Returns the descendants of the specified class
	pub fn descendants_of(&self, cpp_refname: &str) -> Option<&HashSet<Entity<'tu>>> {
		self.descendants.get(cpp_refname)
	}
}

impl fmt::Debug for GeneratorEnv<'_> {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
		f.debug_struct("GeneratorEnv")
			.field("export_map", &format!("{} elements", self.export_map.len()))
			.field("func_comments", &format!("{} elements", self.func_comments.len()))
			.field(
				"class_kind_cache",
				&format!("{} elements", self.class_kind_cache.borrow().len()),
			)
			.finish()
	}
}