Refactor view handlers

doc/notmuch.txt

@@ -292,7 +292,7 @@ option will be listed with its default value.
     - `xdg-open` on Linux
     - `start` on Windows
 
-  Example customization: >
+  Example customization: >lua
 
     require('notmuch').setup({
       open_handler = function(attachment)
@@ -301,6 +301,52 @@ option will be listed with its default value.
     })
 <
 
+*view_handlers*
+  table of handlers to try for converting attachments to text for display
+  in a floating terminal within Neovim. Each handler contains the following keys:
+  - `mime` (string, mandatory): a |lua-pattern| against which the file's mime type
+    (obtained through `file --mime-type --brief`) is matched.
+  - `desc` (string, optional) an optional description, which is used as a fallback
+  - `try` (table): contains the actual commands that will be runned; each element
+    must be a table containing:
+    - one of `callback` or `command`.
+      A callback is a lua function taking a path as input
+      and returning:
+      - `success` (boolean): wether the command succeeded
+      - `output` (string, necessary only if success is true):
+      - `error` (string): an optional error message to be displayed if `success` is false
+        and `verbose` is true
+      A command is a function taking a path as its argument and returning either a
+      string (in which case `vim.fn.system` is used), either a table of strings (in
+      which case `vim.system` is used) either a table of tables of strings (the
+      commands will be runned one after the other through `vim.system`, the output
+      of the previous becoming the input of the next; if one fails, subsequent
+      command execution is stopped).
+    - `tool` (optional): used in notifications
+    - `verbose` (boolean): wether to notify on failure
+
+  Example customization: >lua
+
+    require('notmuch').setup({
+      view_handlers = {
+        {
+          mime = "^application/pdf$",
+          desc = "View with poppler and kitty image protocol",
+          try = {
+            {
+              mime = "^application/x-pie-executable$"
+              tool = "hexyl",
+              verbose = true,
+              command = function(p)
+                return { "hexyl", "--color=never", p }
+              end,
+            },
+          },
+        },
+      },
+    })
+<
+
 *view_handler*
   Callback function for converting attachments to text for display in a
   floating window within Neovim. The function receives an attachment table
@@ -312,7 +358,7 @@ option will be listed with its default value.
     HTML, pdftotext/mutool for PDF) and falls back gracefully if tools aren't
     available.
 
-  Example customization: >
+  Example customization: >lua
 
     require('notmuch').setup({
       view_handler = function(attachment)
@@ -344,7 +390,7 @@ option will be listed with its default value.
   Default value:
     `false`
 
-  Example: >
+  Example: >lua
 
     require('notmuch').setup({
       suppress_deprecation_warning = true,
@@ -367,7 +413,7 @@ option will be listed with its default value.
   Default value:
     `false`
 
-  Example: >
+  Example: >lua
 
     require('notmuch').setup({
       render_html_body = true,
@@ -493,7 +539,7 @@ interact with your email directly from the editor.
     `{index}/{total} {sender_name} [📎{attachment_count}]`
     Example: "2/5 John Doe 📎1"
 
-  Example statusline integration with lualine: >
+  Example statusline integration with lualine: >lua
 
     require('lualine').setup({
       sections = {
@@ -506,7 +552,7 @@ interact with your email directly from the editor.
       },
     })
 <
-  Example custom keymap using buffer variables: >
+  Example custom keymap using buffer variables: >lua
 
     vim.keymap.set('n', '<leader>mt', function()
       local thread = vim.b.notmuch_thread

lua/notmuch/config.lua

@@ -60,6 +60,7 @@ C.defaults = function()
     open_handler = function(attachment)
       require('notmuch.handlers').default_open_handler(attachment)
     end,
+    view_handlers = {},
     view_handler = function(attachment)
       return require('notmuch.handlers').default_view_handler(attachment)
     end,

lua/notmuch/handlers.lua

@@ -30,98 +30,102 @@ H.default_view_handler = function(attachment)
   local path = attachment.path -- Already expanded, careful to escape
 
   -- Helper function to "try" commands in order until one works
-  local function try_commands(commands)
-    for _, cmd in ipairs(commands) do
-      -- Check if the tool exists
-      if vim.fn.executable(cmd.tool) == 1 then
-        local output
-        local success
-        local command = cmd.command(path)
-        if type(command) == 'table' then
-          local obj = vim.system(command):wait()
-          output = obj.stdout
-          success = (obj.code == 0)
-        else
-          output = vim.fn.system(command)
-          success = (vim.v.shell_error == 0)
-        end
-
-        if success then
-          return output
-        end
-      end
-    end
-    return nil
+  local try_commands = function(arg)
+    return require("notmuch.util").try_commands(arg, path)
   end
 
   -- Detect file type
-  local filetype = vim.fn.system({ 'file', '--mime-type', '-b', path }):gsub('%s+$', '')
-  local ext = path:match('%.([^%.]+)$') or ''
-
-  -- HTML files (most common)
-  if filetype:match('^text/html$') or ext:match('^html?$') then
-    return try_commands({
-      { tool = 'w3m',    command = function(p) return { 'w3m', '-T', 'text/html', '-dump', p } end },
-      { tool = 'lynx',   command = function(p) return { 'lynx', '-dump', '-nolist', p } end },
-      { tool = 'elinks', command = function(p) return { 'elinks', '-dump', '-no-references', p } end },
-    }) or "HTML file (install w3m, lynx, or elinks to view)"
-  end
-
-  -- PDF files
-  if filetype:match('^application/pdf$') or ext == 'pdf' then
-    return try_commands({
-      { tool = 'pdftotext', command = function(p) return { 'pdftotext', '-layout', p, '-' } end },
-      { tool = 'mutool',    command = function(p) return { 'mutool', 'draw', '-F', 'txt', p } end },
-    }) or "PDF file (install pdftotext or mutool to view)"
-  end
-
-  -- Images
-  if filetype:match('^image/') then
-    return try_commands({
-      { tool = 'chafa',    command = function(p) return { 'chafa', '--size', '80x40', p } end },
-      { tool = 'catimg',   command = function(p) return { 'catimg', '-w', '80', p } end },
-      { tool = 'viu',      command = function(p) return { 'viu', '-w', '80', p } end },
-      { tool = 'exiftool', command = function(p) return { 'exiftool', p } end },
-      { tool = 'identify', command = function(p) return { 'identify', '-verbose', p } end },
-    }) or "Image file (install chafa, viu, or exiftool to view)"
-  end
-
-  -- Office documents (docx, xlsx, pptx)
-  if filetype:match('officedocument') or ext:match('^(docx?|xlsx?|pptx?)$') then
-    return try_commands({
-      { tool = 'pandoc',   command = function(p) return { 'pandoc', '-t', 'plain', p } end },
-      { tool = 'docx2txt', command = function(p) return { 'docx2txt', p, '-' } end },
-    }) or "Office document (install pandoc or docx2txt to view)"
-  end
-
-  -- Markdown
-  if filetype:match('^text/markdown$') or ext:match('^md$') then
-    return try_commands({
-      { tool = 'pandoc', command = function(p) return { 'pandoc', '-t', 'plain', p } end },
-      { tool = 'mdcat',  command = function(p) return { 'mdcat', p } end },
-    }) or vim.fn.system({ 'cat', path })
-  end
-
-  -- Archives (zip, tar, tar.gz, etc.)
-  if filetype:match('zip') or ext == 'zip' then
-    return vim.fn.system({ 'unzip', '-l', path })
-  end
-  if filetype:match('tar') or ext:match('^tar%.?') then
-    return vim.fn.system({ 'tar', '-tvf', path })
-  end
-
-  -- Plain text (fallback for text/*)
-  if filetype:match('^text/') then
-    return vim.fn.system({ 'cat', path })
+  local filetype = vim.fn.system({ "file", "--mime-type", "-b", path }):gsub("%s+$", "")
+
+  local default = {
+    {
+      mime = "^text/html$",
+      desc = "HTML file (install w3m, lynx, or elinks to view)",
+      try = {
+        { tool = "w3m", command = function(p) return { "w3m", "-T", "text/html", "-dump", p } end },
+        { tool = "lynx", command = function(p) return { "lynx", "-dump", "-nolist", p } end },
+        { tool = "elinks", command = function(p) return { "elinks", "-dump", "-no-references", p } end },
+      },
+    },
+    {
+      mime = "^application/pdf$",
+      desc = "PDF file (install pdftotext or mutool to view)",
+      try = {
+        { tool = "pdftotext", command = function(p) return { "pdftotext", "-layout", p, "-" } end },
+        { tool = "mutool", command = function(p) return { "mutool", "draw", "-F", "txt", p } end },
+      },
+    },
+    {
+      mime = "^image/",
+      desc = "Image file (install chafa, viu, or exiftool to view)",
+      try = {
+        { tool = "chafa", command = function(p) return { "chafa", "--size", "80x40", p } end },
+        { tool = "catimg", command = function(p) return { "catimg", "-w", "80", p } end },
+        { tool = "viu", command = function(p) return { "viu", "-w", "80", p } end },
+        { tool = "exiftool", command = function(p) return { "exiftool", p } end },
+        { tool = "identify", command = function(p) return { "identify", "-verbose", p } end },
+      },
+    },
+    {
+      mime = "officedocument",
+      desc = "Office document (install pandoc or docx2txt to view)",
+      try = {
+        { tool = "pandoc", command = function(p) return { "pandoc", "-t", "plain", p } end },
+        { tool = "docx2txt", command = function(p) return { "docx2txt", p, "-" } end },
+      },
+    },
+    {
+      mime = "^text/markdown$",
+      try = {
+        { tool = "pandoc", command = function(p) return { "pandoc", "-t", "plain", p } end },
+        { tool = "mdcat", command = function(p) return { "mdcat", p } end },
+        { tool = "cat", command = function(p) return { "cat", p } end },
+      },
+    },
+    {
+      mime = "zip",
+      try = {
+        { tool = "zip", command = function(p) return { "unzip", "-l", p } end },
+      },
+    },
+    {
+      mime = "tar",
+      try = {
+        { tool = "tar", command = function(p) return { "tar", "-tvf", p } end },
+      },
+    },
+    {
+      mime = "^text/",
+      try = {
+        { tool = "cat", command = function(p) return { "cat", p } end },
+      },
+    },
+    {
+      mime = "",
+      desc = string.format(
+        "Unable to view binary file\nType: %s\nPath: %s",
+        filetype,
+        path
+      ),
+      try = {
+        { tool = "strings", command = function(p) return { "strings", p } end },
+      },
+    },
+  }
+
+  -- ensure user_config overrides default
+  local user_config = require("notmuch.config").options.view_handlers
+  local handlers = vim.iter({ user_config, default }):flatten():totable()
+
+  for _, tbl in ipairs(handlers) do
+    if filetype:match(tbl.mime) then
+      return try_commands(tbl.try) or tbl.desc or ""
+    end
   end
 
-  return try_commands({
-    { tool = 'strings', command = function(p) return { 'strings', p } end },
-  }) or string.format(
-    "Unable to view binary file\nType: %s\nPath: %s",
-    filetype,
-    path
-  )
+  return "No handler found for this filetype"
 end
 
 return H
+
+-- vim: tabstop=2:shiftwidth=2:expandtab

lua/notmuch/util.lua

@@ -252,6 +252,48 @@ u.find_cursor_msg_id = function()
   return nil
 end
 
+function u.try_commands(commands, path)
+  for _, cmd in ipairs(commands) do
+    local output
+    local success
+    local error
+
+    if cmd.callback then
+      success, output, error = cmd.callback(path)
+    elseif cmd.command then
+      local command = cmd.command(path)
+      if type(command) == "table" then
+        -- use vim.system
+        -- { ... }: convert to { { ... } }
+        if #command > 0 and type(command[1]) == "string" then
+          command = { command }
+        end
+        -- { { ... }, { ... } }: pipe the output of a command to the next
+        for _, cmd in ipairs(command) do
+          local obj = vim.system(cmd, { stdin = output }):wait()
+          output = obj.stdout
+          success = (obj.code == 0)
+          error = obj.stderr
+          if not success then break end
+        end
+      elseif type(command) == "string" then
+        -- use vim.fn.system
+        output = vim.fn.system(command)
+        success = (vim.v.shell_error == 0)
+      end
+    end
+
+    if success then
+      return output
+    else
+      if error and cmd.verbose then
+        vim.notify("failed to execute " .. (cmd.tool or "") .. ": " .. error, vim.log.levels.ERROR)
+      end
+    end
+  end
+  return nil
+end
+
 return u
 
 -- vim: tabstop=2:shiftwidth=2:expandtab:foldmethod=indent