feat: add use_cached mode

Changes:
- Update docs to include use_cached mode
- Add validation checks
- Add support for use_cached mode

code-server/README.md

@@ -80,9 +80,23 @@ module "code-server" {
 }
 ```
 
-### Offline Mode
+### Offline and Use Cached Modes
 
-Run an existing copy of code-server if found, otherwise download from GitHub. By default the module looks for code-server at `/tmp/code-server` but this can be changed with `install_prefix`.
+By default the module looks for code-server at `/tmp/code-server` but this can be changed with `install_prefix`.
+
+Run an existing copy of code-server if found, otherwise download from GitHub:
+
+```tf
+module "code-server" {
+  source     = "registry.coder.com/modules/code-server/coder"
+  version    = "1.0.8"
+  agent_id   = coder_agent.example.id
+  use_cached = true
+  extensions = ["dracula-theme.theme-dracula", "ms-azuretools.vscode-docker"]
+}
+```
+
+Just run code-server in the background, don't fetch it from GitHub:
 
 ```tf
 module "code-server" {

code-server/main.tf

@@ -89,6 +89,12 @@ variable "offline" {
   default     = false
 }
 
+variable "use_cached" {
+  type        = bool
+  description = "Uses cached copy code-server in the background, otherwise fetched it from GitHub"
+  default     = false
+}
+
 resource "coder_script" "code-server" {
   agent_id     = var.agent_id
   display_name = "code-server"
@@ -103,8 +109,21 @@ resource "coder_script" "code-server" {
     // This is necessary otherwise the quotes are stripped!
     SETTINGS : replace(jsonencode(var.settings), "\"", "\\\""),
     OFFLINE : var.offline,
+    USE_CACHED : var.use_cached,
   })
   run_on_start = true
+
+  lifecycle {
+    precondition {
+      condition     = !var.offline || length(var.extensions) == 0
+      error_message = "Offline mode does not allow extensions to be installed"
+    }
+
+    precondition {
+      condition     = !var.offline || !var.use_cached
+      error_message = "Offline and Use Cached can not be used together"
+    }
+  }
 }
 
 resource "coder_app" "code-server" {

code-server/run.sh

@@ -19,10 +19,18 @@ if [ ! -f ~/.local/share/code-server/User/settings.json ]; then
   echo "${SETTINGS}" > ~/.local/share/code-server/User/settings.json
 fi
 
-if [ "${OFFLINE}" = true ] && [ -f $CODE_SERVER ]; then
-  echo "🥳 Found offline copy of code-server"
+# Check if code-server is already installed for offline or cached mode
+if [ -f $CODE_SERVER ]; then
+  if "${OFFLINE}" = true || "${USE_CACHED}" = true; then
+    echo "🥳 Found a copy of code-server"
     run_code_server
     exit 0
+  fi
+fi
+# Offline mode always expects a copy of code-server to be present
+if [ "${OFFLINE}" = true ]; then
+  echo "Failed to find a copy of code-server"
+  exit 1
 fi
 
 printf "$${BOLD}Installing code-server!\n"