// Packages represented on ASG
//
//  Copyright (C) 2014-2023 Ryan Specialty, LLC.
//
//  This file is part of TAME.
//
//  This program is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program.  If not, see <http://www.gnu.org/licenses/>.

//! Package object on the ASG.

use super::{prelude::*, Doc, Ident, NameableMissingObject, Tpl};
use crate::{
    f::Functor,
    fmt::{DisplayWrapper, TtQuote},
    parse::{util::SPair, Token},
    span::Span,
};
use std::fmt::Display;

#[cfg(doc)]
use super::ObjectKind;

#[derive(Debug, PartialEq, Eq)]
pub struct Pkg(Span, PathSpec);

impl Pkg {
    /// Create a new package intended to serve as the compilation unit,
    ///   with an empty pathspec.
    pub fn new<S: Into<Span>>(span: S) -> Self {
        Self(span.into(), PathSpec::Unnamed)
    }

    /// Represent a package imported according to the provided
    ///   [`PathSpec`].
    pub fn new_imported(pathspec: SPair) -> Self {
        Self(pathspec.span(), PathSpec::TodoImport(pathspec))
    }

    pub fn span(&self) -> Span {
        match self {
            Self(span, _) => *span,
        }
    }

    /// Attempt to assign a canonical name to this package.
    ///
    /// Only [`PathSpec::Unnamed`] packages may have a named assigned,
    ///   otherwise an [`AsgError::PkgRename`] [`Err`] will be returned.
    pub fn assign_canonical_name(
        self,
        name: SPair,
    ) -> Result<Self, (Self, AsgError)> {
        match self {
            Self(span, PathSpec::Unnamed) => {
                Ok(Self(span, PathSpec::Canonical(name)))
            }
            Self(_, PathSpec::Canonical(orig) | PathSpec::TodoImport(orig)) => {
                Err((self, AsgError::PkgRename(orig, name)))
            }
        }
    }

    /// The canonical name for this package assigned by
    ///   [`Self::assign_canonical_name`],
    ///     if any.
    pub fn canonical_name(&self) -> Option<SPair> {
        match self {
            Self(_, pathspec) => pathspec.canonical_name(),
        }
    }

    /// The import path to this package as provided by
    ///   [`Self::new_imported`],
    ///     if any.
    pub fn import_path(&self) -> Option<SPair> {
        match self {
            Self(_, pathspec) => pathspec.import_path(),
        }
    }
}

impl Display for Pkg {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        write!(f, "package")
    }
}

impl NameableMissingObject for Pkg {
    fn missing(pathspec: SPair) -> Self {
        Self::new_imported(pathspec)
    }
}

impl Functor<Span> for Pkg {
    fn map(self, f: impl FnOnce(Span) -> Span) -> Self::Target {
        match self {
            Self(span, path) => Self(f(span), path),
        }
    }
}

#[derive(Debug, PartialEq, Eq)]
enum PathSpec {
    /// Unnamed package.
    Unnamed,

    /// Canonical package name.
    ///
    /// This is the name of the package relative to the project root.
    /// This is like the module name after `crate::` in Rust,
    ///   but with `/` package separators in place of `::`.
    Canonical(SPair),

    /// Import path relative to the current package
    ///   (which is likely the compilation unit).
    ///
    /// TODO: This will be replaced with [`Self::Canonical`] once that is
    ///   working and relative paths can be resolved against the active
    ///   package.
    TodoImport(SPair),
}

impl PathSpec {
    fn canonical_name(&self) -> Option<SPair> {
        use PathSpec::*;

        match self {
            Unnamed => None,
            Canonical(spair) => Some(*spair),
            TodoImport(_) => None,
        }
    }

    fn import_path(&self) -> Option<SPair> {
        use PathSpec::*;

        match self {
            Unnamed => None,
            // TODO: Let's wait to see if we actually need this,
            //   since we'll need to allocate and intern a `/`-prefixed
            //   symbol.
            Canonical(_) => None,
            TodoImport(spair) => Some(*spair),
        }
    }
}

impl Display for PathSpec {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        use PathSpec::*;

        match self {
            Unnamed => {
                write!(f, "unnamed package")
            }
            Canonical(spair) => write!(f, "package {}", TtQuote::wrap(spair)),
            TodoImport(spair) => write!(
                f,
                "package import {} relative to compilation unit",
                TtQuote::wrap(spair)
            ),
        }
    }
}

object_rel! {
    /// Packages serve as a root for all identifiers defined therein,
    ///   and so an edge to [`Ident`] will never be a cross edge.
    ///
    /// Imported [`Ident`]s do not have edges from this package.
    Pkg -> {
        // Package import
        cross Pkg,

        // Identified objects owned by this package.
        tree Ident,

        // Anonymous templates are used for expansion.
        tree Tpl,

        // Arbitrary blocks of text serving as documentation.
        tree Doc,
    }
}

impl ObjectIndex<Pkg> {
    /// Complete the definition of a package.
    pub fn close(self, asg: &mut Asg, span: Span) -> Self {
        self.map_obj(asg, Pkg::fmap(|open| open.merge(span).unwrap_or(open)))
    }

    /// Attempt to assign a canonical name to this package.
    ///
    /// This assignment will fail if the package either already has a name
    ///   or if a package of the same name has already been declared.
    pub fn assign_canonical_name(
        self,
        asg: &mut Asg,
        name: SPair,
    ) -> Result<Self, AsgError> {
        let oi_root = asg.root(name);

        asg.try_index(oi_root, name, self).map_err(|oi_prev| {
            let prev = oi_prev.resolve(asg);

            // unwrap note: a canonical name must exist for this error to
            //   have been thrown,
            //     but this will at least not blow up if something really
            //     odd happens.
            AsgError::PkgRedeclare(prev.canonical_name().unwrap_or(name), name)
        })?;

        self.try_map_obj(asg, |pkg| pkg.assign_canonical_name(name))
    }

    /// Indicate that a package should be imported at the provided
    ///   pathspec.
    ///
    /// This simply adds the import to the graph;
    ///   package loading must be performed by another subsystem.
    pub fn import(self, asg: &mut Asg, pathspec: SPair) -> Self {
        let oi_import = asg.create(Pkg::new_imported(pathspec));
        self.add_edge_to(asg, oi_import, Some(pathspec.span()))
    }

    /// Arbitrary text serving as documentation in a literate style.
    pub fn append_doc_text(&self, asg: &mut Asg, text: SPair) -> Self {
        let oi_doc = asg.create(Doc::new_text(text));
        self.add_edge_to(asg, oi_doc, None)
    }
}