From a25ec00f8886c9b87e9423aedd498cec9419508b Mon Sep 17 00:00:00 2001
From: Christian Clason <c.clason@uni-graz.at>
Date: Tue, 22 Oct 2024 00:18:16 +0200
Subject: [PATCH] vim-patch:421ed14: runtime(typst): add folding to typst
 ftplugin

closes: vim/vim#15897

https://github.com/vim/vim/commit/421ed14b8a0f50e0d2d9247dda49feb69352bd0d

Co-authored-by: Luca Saccarola <github.e41mv@aleeas.com>
---
 runtime/autoload/typst.vim | 27 ++++++++++++++++++++++++++-
 runtime/doc/filetype.txt   | 13 +++++++++++++
 runtime/ftplugin/typst.vim |  8 +++++++-
 3 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/runtime/autoload/typst.vim b/runtime/autoload/typst.vim
index 55edd23928..baf765a30b 100644
--- a/runtime/autoload/typst.vim
+++ b/runtime/autoload/typst.vim
@@ -1,6 +1,6 @@
 " Language:    Typst
 " Maintainer:  Gregory Anders
-" Last Change: 2024-07-14
+" Last Change: 2024 Oct 21
 " Based on:    https://github.com/kaarmu/typst.vim
 
 function! typst#indentexpr() abort
@@ -31,6 +31,31 @@ function! typst#indentexpr() abort
     return l:ind
 endfunction
 
+function typst#foldexpr()
+    let line = getline(v:lnum)
+
+    " Whenever the user wants to fold nested headers under the parent
+    let nested = get(g:, "typst_foldnested", 1)
+
+    " Regular headers
+    let depth = match(line, '\(^=\+\)\@<=\( .*$\)\@=')
+
+    " Do not fold nested regular headers
+    if depth > 1 && !nested
+        let depth = 1
+    endif
+
+    if depth > 0
+        " check syntax, it should be typstMarkupHeading
+        let syncode = synstack(v:lnum, 1)
+        if len(syncode) > 0 && synIDattr(syncode[0], 'name') ==# 'typstMarkupHeading'
+            return ">" . depth
+        endif
+    endif
+
+    return "="
+endfunction
+
 " Gets the previous non-blank line that is not a comment.
 function! s:get_prev_nonblank(lnum) abort
     let l:lnum = prevnonblank(a:lnum)
diff --git a/runtime/doc/filetype.txt b/runtime/doc/filetype.txt
index a577b0c5fb..a0f2abbb44 100644
--- a/runtime/doc/filetype.txt
+++ b/runtime/doc/filetype.txt
@@ -1039,6 +1039,19 @@ TYPST							*ft-typst-plugin*
 							*g:typst_conceal*
 When |TRUE| the Typst filetype plugin will set the 'conceallevel' option to 2.
 
+							*g:typst_folding*
+When |TRUE| the Typst filetype plugin will fold headings. (default: |FALSE|)
+
+To enable: >
+	let g:typst_folding = 1
+<
+							*g:typst_foldnested*
+When |TRUE| the Typst filetype plugin will fold nested heading under their parents
+(default: |TRUE|)
+
+To disable: >
+	let g:typst_foldnested = 0
+<
 VIM							*ft-vim-plugin*
 
 The Vim filetype plugin defines mappings to move to the start and end of
diff --git a/runtime/ftplugin/typst.vim b/runtime/ftplugin/typst.vim
index 895fc688d9..3841e427f3 100644
--- a/runtime/ftplugin/typst.vim
+++ b/runtime/ftplugin/typst.vim
@@ -1,7 +1,7 @@
 " Vim filetype plugin file
 " Language:    Typst
 " Maintainer:  Gregory Anders
-" Last Change: 2024 Oct 04
+" Last Change: 2024 Oct 21
 " Based on:    https://github.com/kaarmu/typst.vim
 
 if exists('b:did_ftplugin')
@@ -21,6 +21,12 @@ if get(g:, 'typst_conceal', 0)
   let b:undo_ftplugin .= ' cole<'
 endif
 
+if has("folding") && get(g:, 'typst_folding', 0)
+    setlocal foldexpr=typst#foldexpr()
+    setlocal foldmethod=expr
+    let b:undo_ftplugin .= "|setl foldexpr< foldmethod<"
+endif
+
 if !exists('current_compiler')
   compiler typst
   let b:undo_ftplugin ..= "| compiler make"