use super::config::Config;
use super::entities::*;
use crate::types::Entity;

use anyhow::{anyhow, Context, Error, Result};
use clang::{Clang, CompilationDatabase, Index, TranslationUnit, Usr};
use codemap::CodeMap;
use thiserror::Error;

use std::collections::BTreeMap;
use std::convert::{TryFrom, TryInto};
use std::path::{Path, PathBuf};

#[derive(Debug, Default)]
struct TopLevel {
    namespaces: BTreeMap<Usr, Described<Namespace>>,
    variables: BTreeMap<Usr, Described<Variable>>,
    structs: BTreeMap<Usr, Described<Struct>>,
    functions: BTreeMap<Usr, Described<Function>>,
}

/*
enum TopLevelEntry<'a, T> {
    Vacant {
        parent: &'a mut Described<Namespace>,
    },
    /// Vacant, but no semantic parent
    TopLevel,
    Occupied {
        entity: &'a mut Described<T>,
    },
    Error,
}
*/

impl TopLevel {
    // Somehow has a lifetime issue I can't get my head around
    /*
    fn entry<'a, T>(&'a mut self, path: &::clang::Entity) -> Result<TopLevelEntry<'a, T>>
    where
        T: ClangEntity + FromNamespaceParent + FromTopLevel,
    {
        let usr = path.get_usr().ok_or_else(|| anyhow!("no usr"))?;
        if let Some(parent_path) = parent(&path) {
            let parent_entry = self.entry::<Namespace>(&parent_path)?;
            if let TopLevelEntry::Occupied {
                entity: namespace_parent,
            } = parent_entry
            {
                Ok(match T::from_namespace_parent(namespace_parent, &usr) {
                    None => TopLevelEntry::Vacant {
                        parent: namespace_parent,
                    },
                    Some(entity) => TopLevelEntry::Occupied { entity },
                })
            } else {
                panic!("Wut");
            }
        } else {
            Ok(match T::from_toplevel(self, &usr) {
                Some(entity) => TopLevelEntry::Occupied { entity },
                None => TopLevelEntry::TopLevel,
            })
        }
    }
    */

    fn get_entity_mut(&mut self, path: clang::Entity) -> Option<&mut dyn ClangEntity> {
        let usr = path.get_usr()?;
        if let Some(parent_path) = parent(path) {
            let parent = self.get_entity_mut(parent_path)?;
            Some(match path.get_kind().try_into().ok()? {
                ClangEntityKind::Namespace => {
                    &mut parent.get_member_namespaces()?.get_mut(&usr)?.entity
                }
                ClangEntityKind::Variable(_) => {
                    &mut parent.get_member_variables()?.get_mut(&usr)?.entity
                }
                ClangEntityKind::Function(_) => {
                    &mut parent.get_member_functions()?.get_mut(&usr)?.entity
                }
                ClangEntityKind::Struct(_) => {
                    &mut parent.get_member_structs()?.get_mut(&usr)?.entity
                }
            })
        } else {
            Some(match path.get_kind().try_into().ok()? {
                ClangEntityKind::Namespace => &mut self.namespaces.get_mut(&usr)?.entity,
                ClangEntityKind::Variable(_) => &mut self.variables.get_mut(&usr)?.entity,
                ClangEntityKind::Struct(_) => &mut self.structs.get_mut(&usr)?.entity,
                ClangEntityKind::Function(_) => &mut self.functions.get_mut(&usr)?.entity,
            })
        }
    }

    fn get_namespace_mut(&mut self, path: clang::Entity) -> Option<&mut Described<Namespace>> {
        let usr = path.get_usr()?;

        if let Some(parent_path) = parent(path) {
            let parent = self.get_entity_mut(parent_path)?;
            parent.get_member_namespaces()?.get_mut(&usr)
        } else {
            self.namespaces.get_mut(&usr)
        }
    }

    fn insert<T>(&mut self, path: clang::Entity, entity: Described<T>) -> Result<()>
    where
        T: ClangEntity + std::fmt::Debug,
        Self: TopLevelManipulation<T>,
        Namespace: NamespaceParentManipulation<T>,
    {
        let usr = path.get_usr().ok_or_else(|| anyhow!("no usr"))?;
        if let Some(parent_path) = parent(path) {
            if let Some(parent_namespace) = self.get_namespace_mut(parent_path) {
                parent_namespace
                    .entity
                    .get_members_mut()
                    // Namespace should be able to contain every kind of entity
                    .unwrap()
                    .insert(usr, entity);
                Ok(())
            } else {
                Err(anyhow!("has parent but no parent in tree"))
            }
        } else {
            self.insert_toplevel(usr, entity);
            Ok(())
        }
    }
}

// Like .get_semantic_parent(), but return none if the parent is the translation unit
fn parent(libclang_entity: clang::Entity) -> Option<clang::Entity> {
    match libclang_entity.get_semantic_parent() {
        Some(parent) => {
            if parent.get_kind() != clang::EntityKind::TranslationUnit {
                Some(parent)
            } else {
                None
            }
        }
        None => {
            warn!("get_semantic_parent() returned None");
            None
        }
    }
}

trait TopLevelManipulation<T: ClangEntity> {
    fn insert_toplevel(&mut self, usr: Usr, entity: Described<T>);
}

impl TopLevelManipulation<Namespace> for TopLevel {
    fn insert_toplevel(&mut self, usr: Usr, entity: Described<Namespace>) {
        self.namespaces.insert(usr, entity);
    }
}

impl TopLevelManipulation<Variable> for TopLevel {
    fn insert_toplevel(&mut self, usr: Usr, entity: Described<Variable>) {
        self.variables.insert(usr, entity);
    }
}

impl TopLevelManipulation<Function> for TopLevel {
    fn insert_toplevel(&mut self, usr: Usr, entity: Described<Function>) {
        self.functions.insert(usr, entity);
    }
}

impl TopLevelManipulation<Struct> for TopLevel {
    fn insert_toplevel(&mut self, usr: Usr, entity: Described<Struct>) {
        self.structs.insert(usr, entity);
    }
}

/*
trait FromTopLevel: ClangEntity + Sized {
    fn from_toplevel<'a>(toplevel: &'a mut TopLevel, usr: &Usr) -> Option<&'a mut Described<Self>>;
}

impl FromTopLevel for Namespace {
    fn from_toplevel<'a>(toplevel: &'a mut TopLevel, usr: &Usr) -> Option<&'a mut Described<Self>> {
        toplevel.namespaces.get_mut(usr)
    }
}

impl FromTopLevel for Variable {
    fn from_toplevel<'a>(toplevel: &'a mut TopLevel, usr: &Usr) -> Option<&'a mut Described<Self>> {
        toplevel.variables.get_mut(usr)
    }
}

impl FromTopLevel for Function {
    fn from_toplevel<'a>(toplevel: &'a mut TopLevel, usr: &Usr) -> Option<&'a mut Described<Self>> {
        toplevel.functions.get_mut(usr)
    }
}

impl FromTopLevel for Struct {
    fn from_toplevel<'a>(toplevel: &'a mut TopLevel, usr: &Usr) -> Option<&'a mut Described<Self>> {
        toplevel.structs.get_mut(usr)
    }
}
*/

pub(crate) fn parse_compile_commands(
    config: &Config,
    codemap: &mut CodeMap,
) -> Result<BTreeMap<String, Entity>> {
    let clang = Clang::new().unwrap();
    let index = Index::new(
        &clang, /* exclude from pch = */ false, /* print diagnostics = */ false,
    );

    debug!("Extra libclang argument: {:?}", config.extra_args);

    debug!(
        "Loading compile commands from: {:?}",
        config.compile_commands_location
    );
    let database =
        CompilationDatabase::from_directory(&config.compile_commands_location).map_err(|()| {
            CompileCommandsLoadError {
                path: config.compile_commands_location.clone(),
            }
        })?;

    let toplevel_directory = std::env::current_dir().context("Cannot read current directory")?;

    let mut entities = TopLevel::default();

    for command in database.get_all_compile_commands().get_commands() {
        let directory = command.get_directory();
        trace!("Changing directory to: {:?}", directory);
        std::env::set_current_dir(&directory)
            .with_context(|| format!("Cannot change current directory to: {:?}", directory))?;

        let filename = command.get_filename();

        let file_map = codemap.add_file(
            filename
                .to_str()
                .context("File is not valid UTF-8")?
                .to_owned(),
            std::fs::read_to_string(&filename)
                .with_context(|| format!("Cannot readfile: {:?}", filename))?,
        );

        trace!("Parsing file: {:?}", filename);
        // The file name is passed as an argument in the compile commands
        let mut parser = index.parser("");
        parser.skip_function_bodies(true);

        let mut clang_arguments = command.get_arguments();
        clang_arguments.extend_from_slice(&config.extra_args);
        trace!("Parsing with libclang arguments: {:?}", clang_arguments);
        parser.arguments(&clang_arguments);

        parse_unit(
            &parser
                .parse()
                .with_context(|| format!("Could not parse file: {:?}", filename))?,
            &mut entities,
            &toplevel_directory,
            file_map.span,
            &codemap,
        )?;

        trace!("Changing directory to: {:?}", directory);
        std::env::set_current_dir(&toplevel_directory).with_context(|| {
            format!(
                "Cannot change current directory to: {:?}",
                toplevel_directory
            )
        })?;
    }

    let normalized_entities = entities
        .namespaces
        .into_iter()
        .map(|(usr, entity)| (usr.0, entity.into()))
        .chain(entities.variables.into_iter().map(|(usr, entity)| (usr.0, entity.into())))
        .chain(entities.structs.into_iter().map(|(usr, entity)| (usr.0, entity.into())))
        .chain(entities.functions.into_iter().map(|(usr, entity)| (usr.0, entity.into())))
        .collect();

    Ok(normalized_entities)
}

/*
pub(crate) fn parse_file<T, S>(path: T, extra_args: &[S]) -> EntitiesManager
where
    T: Into<PathBuf>,
    T: AsRef<Path>,
    T: ToString,
    S: AsRef<str>,
    S: std::fmt::Debug,
{
    let mut codemap = CodeMap::new();
    let file_map = codemap.add_file(path.to_string(), std::fs::read_to_string(&path).unwrap());
    let file_span = file_map.span;

    let clang = Clang::new().unwrap();
    let index = Index::new(&clang, true, false);
    let mut parser = index.parser(path);
    parser.skip_function_bodies(true);

    parser.arguments(&extra_args);

    if log_enabled!(log::Level::Debug) {
        for extra_arg in extra_args {
            debug!("Extra libclang argument: {:?}", extra_arg);
        }
    }

    let trans_unit = parser.parse().unwrap();
    let mut entities = EntitiesManager::new();

    parse_unit(
        &trans_unit,
        &mut entities,
        &std::env::current_dir().unwrap(),
        file_span,
        &codemap,
    )
    .unwrap();

    entities
}
*/

fn parse_unit(
    trans_unit: &TranslationUnit,
    entities: &mut TopLevel,
    base_dir: impl AsRef<Path>,
    file_span: codemap::Span,
    codemap: &CodeMap,
) -> Result<()> {
    trans_unit.get_entity().visit_children(|entity, _parent| {
        if is_in_system_header(entity, &base_dir) {
            trace!(
                "Entity is in system header, skipping: USR = {:?}",
                entity.get_display_name()
            );
            return clang::EntityVisitResult::Continue;
        }

        // TODO: wrap this callback in another function so that we can use the
        // "?" operator instead of all these `match`es
        let usr = match entity.get_usr() {
            Some(usr) => usr,
            None => return clang::EntityVisitResult::Continue,
        };
        trace!("Entity with USR = {:?}", usr);
        debug!("Parsing toplevel entity: {:?}", entity);

        add_entity(entity, entities, file_span, codemap)
    });

    /*
    use codemap_diagnostic::{ColorConfig, Emitter};

    let mut emitter = Emitter::stderr(ColorConfig::Auto, Some(&codemap));

    for diagnostic in trans_unit.get_diagnostics().iter() {
        let main_diag = match clang_diag_to_codemap_diag(&diagnostic, file_span) {
            Some(diag) => diag,
            None => continue,
        };

        let sub_diags = diagnostic
            .get_children()
            .into_iter()
            .filter_map(|diagnostic| clang_diag_to_codemap_diag(&diagnostic, file_span));

        let fix_it_diags = diagnostic
            .get_fix_its()
            .into_iter()
            .map(|fix_it| clang_fix_it_to_codemap_diag(&fix_it, file_span));

        emitter.emit(
            &std::iter::once(main_diag)
                .chain(sub_diags)
                .chain(fix_it_diags)
                .collect::<Vec<_>>(),
        );
    }
    */

    Ok(())
}

fn is_in_system_header(entity: clang::Entity, base_dir: impl AsRef<Path>) -> bool {
    if entity.is_in_system_header() {
        true
    } else if let Some(location) = entity.get_location() {
        if let Some(file) = location.get_file_location().file {
            !file
                .get_path()
                .canonicalize()
                .unwrap()
                .starts_with(base_dir)
        } else {
            // Not defined in a file? probably shouldn't document
            true
        }
    } else {
        // Not defined anywhere? probably shouldn't document
        true
    }
}

// Entries encountered in the toplevel lexical context
fn add_entity(
    libclang_entity: clang::Entity,
    toplevel: &mut TopLevel,
    file_span: codemap::Span,
    codemap: &CodeMap,
) -> clang::EntityVisitResult {
    if libclang_entity.get_usr().is_none() {
        return clang::EntityVisitResult::Continue;
    };

    let kind = match ClangEntityKind::try_from(libclang_entity.get_kind()) {
        Ok(kind) => kind,
        Err(err) => {
            use codemap_diagnostic::{
                ColorConfig, Diagnostic, Emitter, Level, SpanLabel, SpanStyle,
            };
            let spans = if let Some(range) = libclang_entity.get_range() {
                // TODO: add every file parsed in this translation unit to the
                // codemap, so we can properly report errors
                if !range.is_in_main_file() {
                    vec![]
                } else {
                    let begin = range.get_start().get_file_location().offset as u64;
                    let end = range.get_end().get_file_location().offset as u64;

                    vec![SpanLabel {
                        span: file_span.subspan(begin, end),
                        label: None,
                        style: SpanStyle::Primary,
                    }]
                }
            } else {
                vec![]
            };

            let diag = Diagnostic {
                level: Level::Warning,
                message: format!("{}", err),
                code: None,
                spans,
            };

            let mut emitter = Emitter::stderr(ColorConfig::Auto, Some(codemap));
            emitter.emit(&[diag]);

            return clang::EntityVisitResult::Continue;
        }
    };

    if let Some(in_tree_entity) = toplevel.get_entity_mut(libclang_entity) {
    // if current.has_documentation && !tree.has_documentation {
    //     append_documentation
    // }
    } else if libclang_entity.is_definition() {
        // TODO: This probably means that you can't put documentation in forward declarations.
        //
        // This seems restrictive, but since there can be multiple declarations but only one definition,
        // you should probably put your documentation on the definition anyway?
        //
        // Also, skipping forward declarations allows us to not have to insert, then update the tree
        // when we see the definition.

        let result = match kind {
            ClangEntityKind::Namespace => Described::<Namespace>::try_from(libclang_entity)
                .and_then(|namespace| toplevel.insert(libclang_entity, namespace)),
            ClangEntityKind::Variable(_) => Described::<Variable>::try_from(libclang_entity)
                .and_then(|variable| toplevel.insert(libclang_entity, variable)),
            ClangEntityKind::Struct(_) => Described::<Struct>::try_from(libclang_entity)
                .and_then(|r#struct| toplevel.insert(libclang_entity, r#struct)),
            ClangEntityKind::Function(_) => Described::<Function>::try_from(libclang_entity)
                .and_then(|function| toplevel.insert(libclang_entity, function)),
        };
        // TODO: check result
    }

    if kind == ClangEntityKind::Namespace {
        // Recurse here since namespace definitions are allowed to change between translation units.
        ::clang::EntityVisitResult::Recurse
    } else {
        ::clang::EntityVisitResult::Continue
    }
}

impl<'a, T> TryFrom<clang::Entity<'a>> for Described<T>
where
    T: TryFrom<clang::Entity<'a>, Error = Error>,
{
    type Error = Error;

    fn try_from(entity: clang::Entity<'a>) -> Result<Self, Error> {
        Ok(Described::<T> {
            description: get_description(entity)?,
            entity: T::try_from(entity)?,
        })
    }
}

impl<'a> TryFrom<clang::Entity<'a>> for Namespace {
    type Error = Error;

    fn try_from(entity: clang::Entity) -> Result<Self, Error> {
        match entity.get_kind().try_into() {
            Ok(ClangEntityKind::Namespace) => {}
            _ => panic!("Trying to parse a non-variable into a variable"),
        }
        debug!("Parsing Namespace: {:?}", entity);

        // Do not recurse here, but recurse in the main loop, since namespace
        // definitions is allowed to change between translation units

        Ok(Namespace {
            member_namespaces: Default::default(),
            member_variables: Default::default(),
            member_structs: Default::default(),
            member_functions: Default::default(),
        })
    }
}

impl<'a> TryFrom<clang::Entity<'a>> for Variable {
    type Error = Error;

    fn try_from(entity: clang::Entity) -> Result<Self, Error> {
        let variable_kind;
        match entity.get_kind().try_into() {
            Ok(ClangEntityKind::Variable(kind)) => {
                variable_kind = kind;
            }
            _ => panic!("Trying to parse a non-variable into a variable"),
        }
        debug!("Parsing Variable: {:?}", entity);

        let r#type = entity.get_type().unwrap().get_display_name();
        trace!("Variable has type: {:?}", r#type);

        Ok(Variable {
            r#type,
            kind: variable_kind,
        })
    }
}

impl<'a> TryFrom<clang::Entity<'a>> for Struct {
    type Error = Error;

    fn try_from(entity: clang::Entity) -> Result<Self, Error> {
        let struct_kind;
        match entity.get_kind().try_into() {
            Ok(ClangEntityKind::Struct(kind)) => {
                struct_kind = kind;
            }
            _ => panic!("Trying to parse a non-class into a class"),
        }
        debug!("Parsing Struct: {:?}", entity);

        let mut member_variables = BTreeMap::new();
        let mut member_structs = BTreeMap::new();
        let mut member_functions = BTreeMap::new();

        for child in entity.get_children() {
            trace!("Struct has child: {:?}", child);

            match child.get_kind().try_into() {
                Ok(ClangEntityKind::Variable(_)) => {
                    let child_usr = child.get_usr().ok_or_else(|| anyhow!("no usr"))?;
                    member_variables.insert(child_usr, Described::<Variable>::try_from(child)?);
                }
                Ok(ClangEntityKind::Struct(_)) => {
                    let child_usr: Usr = child.get_usr().ok_or_else(|| anyhow!("no usr"))?;
                    member_structs.insert(child_usr, Described::<Struct>::try_from(child)?);
                }
                Ok(ClangEntityKind::Function(_)) => {
                    let child_usr = child.get_usr().ok_or_else(|| anyhow!("no usr"))?;
                    member_functions.insert(child_usr, Described::<Function>::try_from(child)?);
                }
                _ => trace!("Skipping child"),
            }
        }

        Ok(Struct {
            kind: struct_kind,
            member_functions,
            member_structs,
            member_variables,
        })
    }
}

impl<'a> TryFrom<clang::Entity<'a>> for Function {
    type Error = Error;

    fn try_from(entity: clang::Entity) -> Result<Self, Error> {
        let function_kind;
        match entity.get_kind().try_into() {
            Ok(ClangEntityKind::Function(kind)) => {
                function_kind = kind;
            }
            _ => panic!("Trying to parse a non-function into a function"),
        }
        debug!("Parsing Function: {:?}", entity);

        let return_type = entity.get_result_type().unwrap().get_display_name();
        trace!("Function has return type: {:?}", return_type);
        let arguments = entity
            .get_arguments()
            .unwrap()
            .into_iter()
            .map(|arg| {
                let name = arg
                    .get_display_name()
                    .unwrap_or_else(|| String::from("unnamed"));
                let r#type = arg.get_type().unwrap().get_display_name();
                trace!("Function has argument {:?} of type {:?}", name, r#type);
                FunctionArgument { name, r#type }
            })
            .collect();

        Ok(Function {
            kind: function_kind,
            arguments,
            return_type,
        })
    }
}

fn get_description(entity: clang::Entity) -> Result<Description> {
    let name = entity
        .get_display_name()
        .ok_or_else(|| anyhow!("Entity has no name: {:?}", entity))?;

    // TODO: is that the best?
    if let (Some(brief), Some(comment)) = (entity.get_comment_brief(), entity.get_comment()) {
        Ok(Description {
            name,
            brief,
            detailed: parse_comment(comment),
        })
    } else {
        Ok(Description {
            name,
            brief: String::new(),
            detailed: String::new(),
        })
    }
}

pub fn parse_comment(raw: String) -> String {
    #[derive(Debug)]
    enum CommentStyle {
        // Comments of type `/**` or `/*!`
        Starred,
        // Comments of type `///`
        SingleLine,
    }

    let mut chars = raw.chars();
    let style = match &chars.as_str()[..3] {
        "/*!" | "/**" => CommentStyle::Starred,
        "///" => CommentStyle::SingleLine,
        _ => panic!("Comment is empty or doesn't start with either `///`, `/**`, or `/*!`"),
    };

    chars.nth(2);

    let mut result = String::new();

    'parse_loop: loop {
        let maybe_space = chars.next();
        let mut empty_line = false;
        match maybe_space {
            // TODO: Warn on empty comments
            None => break,
            Some(' ') => {}
            Some('\n') => {
                empty_line = true;
                result.push('\n');
            }
            Some(ch) => result.push(ch),
        }

        if !empty_line {
            let rest = chars.as_str();
            match rest.find('\n') {
                None => {
                    result.push_str(rest);
                    break;
                }
                Some(position) => {
                    result.push_str(&rest[..=position]);
                    chars.nth(position);
                }
            }
        }

        // Beginning of the line
        let first_non_ws_ch = 'ws_loop: loop {
            let maybe_whitespace = chars.next();
            match maybe_whitespace {
                None => break 'parse_loop,
                Some(ch) if ch.is_whitespace() => continue,
                Some(ch) => break 'ws_loop ch,
            }
        };

        match style {
            CommentStyle::Starred if first_non_ws_ch == '*' => {
                if &chars.as_str()[..1] == "/" {
                    break;
                }
            }
            CommentStyle::Starred => result.push(first_non_ws_ch),
            CommentStyle::SingleLine => {
                assert!(first_non_ws_ch == '/');
                let rest = chars.as_str();
                if &rest[..2] == "//" {
                    chars.nth(1);
                } else if &rest[..1] == "/" {
                    chars.nth(0);
                } else {
                    panic!("Could not parse comment");
                }
            }
        }
    }

    result
}

#[derive(Debug, Clone, Error)]
#[error("Failed to load 'compile_commands.json' at path: {:?}", path)]
pub(crate) struct CompileCommandsLoadError {
    path: PathBuf,
}