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

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

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

// TODO: check for use of Extend instead of loop+insert

pub(crate) fn parse_compile_commands(config: &Config) -> Result<types::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();

        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,
        )?;

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

    Ok(entities.into())
}

pub(crate) fn parse_file<T>(path: T, config: &Config) -> Result<types::Entity>
where
    T: Into<PathBuf>,
    T: AsRef<Path>,
    T: ToString,
{
    let clang = Clang::new().unwrap();
    let index = Index::new(&clang, true, false);

    // as provided in the command line
    let filename = path.to_string();

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

    let maybe_commands = CompilationDatabase::from_directory(&config.compile_commands_location)
        .and_then(|database| database.get_compile_commands(&path))
        .ok();
    let maybe_command = maybe_commands
        .as_ref()
        .and_then(|commands| commands.get_commands().pop());

    let mut clang_arguments = maybe_command
        .map(|command| command.get_arguments())
        .unwrap_or_default();
    clang_arguments.extend_from_slice(&config.extra_args);

    let mut parser = if let Some(command) = maybe_command {
        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))?;
        // If it has the parameters provided by the compilation database,
        // then it knows which file to parse
        index.parser("")
    } else {
        index.parser(path)
    };

    parser.skip_function_bodies(true);

    parser.arguments(&clang_arguments);

    trace!("Parsing with libclang arguments: {:?}", clang_arguments);

    let mut entities = TopLevel::default();

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

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

    Ok(entities.into())
}

fn parse_unit(
    trans_unit: &TranslationUnit,
    entities: &mut TopLevel,
    base_dir: impl AsRef<Path>,
) -> Result<()> {
    trans_unit.get_entity().visit_children(|entity, _parent| {
        if is_in_system_header(entity, &base_dir) {
            trace!("Entity is in system header, skipping: {:?}", entity);
            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)
    });

    for diagnostic in trans_unit.get_diagnostics() {
        let diags = diagnostics::clang_diagnostic_to_diagnostics(diagnostic);
        diagnostics::emit(&diags);
        /*
        let sub_diags = diagnostic
            .get_children()
            .into_iter()
            .filter_map(|diagnostic| clang_diag_to_codemap_diag(&diagnostic, file_span));

        );
        */
    }

    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)
            false
        } 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) -> clang::EntityVisitResult {
    let usr = match libclang_entity.get_usr() {
        None => return clang::EntityVisitResult::Continue,
        Some(usr) => usr,
    };

    let kind = match EntityKind::try_from(libclang_entity.get_kind()) {
        Ok(kind) => kind,
        Err(err) => {
            diagnostics::error(format!("{}", err), libclang_entity);
            return clang::EntityVisitResult::Continue;
        }
    };

    match toplevel.entry_dyn(libclang_entity) {
        Err(err) => diagnostics::error(format!("{}", err), libclang_entity),
        Ok(EntityEntry::Occupied { entity }) => {
            // if current.has_documentation && !tree.has_documentation {
            //     append_documentation
            // }
            //
            // if !curent.has_children && tree.has_children {
            //    parse(tree)
            // }
        }
        Ok(EntityEntry::Vacant { parent: dyn_parent }) => {
            if let Err(err) = libclang_entity
                .try_into()
                .and_then(|entity| dyn_parent.entity.insert(usr, entity))
            {
                diagnostics::error(format!("{}", err), libclang_entity);
                return ::clang::EntityVisitResult::Continue;
            }
        }
    }

    if kind == EntityKind::Namespace && libclang_entity.get_name().is_some() {
        // Recurse here since namespace definitions are allowed to change between translation units.
        ::clang::EntityVisitResult::Recurse
    } else {
        ::clang::EntityVisitResult::Continue
    }
}

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

        // `chars` is right after the first non whitespace character
        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] == "//" || &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,
}