Replace vim-airline with a custom statusline

Finally got round to making a custom statusline after being inspired by
https://pastebin.com/Fm1NEgBf

autoload/airline/themes/fresh.vim

@@ -1,73 +0,0 @@
-" fresh palette
-let g:airline#themes#fresh#palette = {}
-
-" NORMAL mode
-let s:N1 = ['#005f00', '#afdf00', 22, 148, '']
-let s:N2 = ['#ffffff', '#005f00', 15, 22, '']
-let s:N3 = ['#ffffff', '#121212', 15, 233, 'bold']
-let s:W = ['#000000', '#8700df', 232, 92, '']
-let s:E = ['#000000', '#990000', 232, 160]
-let g:airline#themes#fresh#palette.normal =
-      \ airline#themes#generate_color_map(s:N1, s:N2, s:N3)
-let g:airline#themes#fresh#palette.normal.airline_warning = s:W
-let g:airline#themes#fresh#palette.normal.airline_error = s:E
-let g:airline#themes#fresh#palette.normal_modified = {
-      \ 'airline_c': ['#ffffff', '#5f0087', 15, 53, 'bold'], }
-
-" INSERT mode
-let s:I1 = ['#0000df', '#00dfff', 20, 45, '']
-let s:I2 = ['#ffffff', '#005fdf', 15, 26, '']
-let s:I3 = ['#ffffff', '#121212', 15, 233, 'bold']
-let g:airline#themes#fresh#palette.insert =
-      \ airline#themes#generate_color_map(s:I1, s:I2, s:I3)
-let g:airline#themes#fresh#palette.insert.airline_warning = s:W
-let g:airline#themes#fresh#palette.insert.airline_error = s:E
-let g:airline#themes#fresh#palette.insert_modified =
-      \ g:airline#themes#fresh#palette.normal_modified
-let g:airline#themes#fresh#palette.insert_paste = {
-      \ 'airline_a': [s:I1[0], '#ffff00', s:I1[2], 11, ''], }
-
-" REPLACE mode
-let s:R1 = [s:I2[0], '#af0000', s:I2[2], 124, '']
-let s:R2 = ['#ffffff', '#5f0000', 15, 52, '']
-let s:R3 = ['#ffffff', '#121212', 15, 233, 'bold']
-let g:airline#themes#fresh#palette.replace =
-      \ airline#themes#generate_color_map(s:R1, s:R2, s:R3)
-let g:airline#themes#fresh#palette.replace.airline_warning = s:W
-let g:airline#themes#fresh#palette.replace.airline_error = s:E
-let g:airline#themes#fresh#palette.replace_modified =
-      \ g:airline#themes#fresh#palette.normal_modified
-
-" VISAUL mode
-let s:V1 = ['#ff5f00', '#ff5f00', 52, 208, '']
-let s:V2 = ['#ffffff', '#005f00', 15, 124, '']
-let s:V3 = ['#ffffff', '#121212', 15, 233, 'bold']
-let g:airline#themes#fresh#palette.visual =
-      \ airline#themes#generate_color_map(s:V1, s:V2, s:V3)
-let g:airline#themes#fresh#palette.visual.airline_warning = s:W
-let g:airline#themes#fresh#palette.visual.airline_error = s:E
-let g:airline#themes#fresh#palette.visual_modified =
-      \ g:airline#themes#fresh#palette.normal_modified
-
-" INACTIVE mode
-let s:IA1 = ['#4e4e4e', '#1c1c1c', 239, 234, '']
-let s:IA2 = ['#4e4e4e', '#262626', 239, 235, '']
-let s:IA3 = ['#ffffff', '#121212', 15, 233, 'bold']
-let g:airline#themes#fresh#palette.inactive =
-      \ airline#themes#generate_color_map(s:IA1, s:IA2, s:IA3)
-let g:airline#themes#fresh#palette.inactive.airline_warning = s:IA2
-let g:airline#themes#fresh#palette.inactive.airline_error =  s:IA2
-let g:airline#themes#fresh#palette.inactive_modified = {
-      \ 'airline_c': ['#875faf', '', 97, '', ''], }
-
-let g:airline#themes#fresh#palette.accents = {
-      \ 'red': [ '#ff0000' , '' , 160 , ''  ] }
-
-if !get(g:, 'loaded_ctrlp', 0)
-  finish
-endif
-let g:airline#themes#fresh#palette.ctrlp =
-      \ airline#extensions#ctrlp#generate_color_map(
-      \   ['#d7d7ff', '#5f00af', 189, 55, ''],
-      \   ['#ffffff', '#875fd7', 231, 98, ''],
-      \   ['#5f00af', '#ffffff', 55, 231, 'bold'] )

plugin/statusline.vim

@@ -76,12 +76,6 @@ endfunction
 " Define active statusline, this statusline is dynamic with StatusLineLight
 " being updated based on the current mode and only used for current buffer.
 function! statusline#active()
-  " TODO: Specialize for:
-  " * [x] help
-  " * [x] quickfix
-  " * [x] location
-  " * [ ] preview
-  " * [x] terminal
   let l:mode = statusline#mode()
   if &buftype ==# 'help'
     if l:mode ==# 'Normal'
@@ -99,6 +93,11 @@ function! statusline#active()
           \ get(l:info['variables'], 'quickfix_title', ''))
   elseif &buftype ==# 'terminal'
     return statusline#special('StatusLineLight', 'Terminal', '%f')
+  elseif &previewwindow
+    if l:mode ==# 'Normal'
+      let l:mode = 'Preview'
+    endif
+    return statusline#generic('StatusLineLight', l:mode)
   endif
   return statusline#generic('StatusLineLight', l:mode)
 endfunction
@@ -106,12 +105,6 @@ endfunction
 " Define inactive statusline, this remains static until the buffer gains
 " focus again.
 function! statusline#inactive()
-  " TODO: Specialize for:
-  " * [x] help
-  " * [x] quickfix
-  " * [x] location
-  " * [ ] preview
-  " * [x] terminal
   if &buftype ==# 'help'
     let l:statusline = statusline#special('StatusLineDusk', 'Help', '%F')
   elseif &buftype ==# 'quickfix'
@@ -123,6 +116,8 @@ function! statusline#inactive()
           \ get(l:info['variables'], 'quickfix_title', ''))
   elseif &buftype ==# 'terminal'
     let l:statusline = statusline#special('StatusLineDusk', 'Terminal', '%f')
+  elseif &previewwindow
+    let l:statusline = statusline#generic('StatusLineDark', 'Preview')
   else
     let l:statusline = statusline#generic('StatusLineDusk', 'Idle')
   endif