Add support for YAML strategy

Introduces a new 'yaml' strategy using Ansible's `from_yaml` to read
target files. This allows users to group multiple targets with
distinct label sets (e.g., severity or job) within a single file,
optimizing Prometheus file-based service discovery.

- Refactored task structure into `strategy_*.yml` for consistency.
- Extracted shared exporter variable computation.
- Implemented label merging where exporter labels override defaults.
- Included support for groups and hosts without labels to prevent crashes.

PR: (#1) https://github.com/kliwniloc/ansible-role-prometheus-target/pull/1

5 files changed, 109 insertions, 29 deletions

diff --git a/tasks/lineinfile.yml b/tasks/lineinfile.yml
deleted file mode 100644
index 8c60ba0..0000000
--- a/tasks/lineinfile.yml
+++ /dev/null
@@ -1,24 +0,0 @@
----
-- name: Make sure targets are deployed
-  ansible.builtin.lineinfile:
-    path: '{{ (
-           item.path_prefix if item.path_prefix is defined else
-           (prometheus_target_exporter_defaults[item.id].path_prefix
-           | default(prometheus_target_exporter_target_prefix))
-           if item.id is defined)
-           ~
-           (item.path if item.path is defined
-           else prometheus_target_exporter_defaults[item.id].path if item.id is defined) | mandatory }}'
-    line: '{{ prometheus_target_strategy_lineinfile_prefix ~
-           (item.host if item.host is defined else prometheus_target_exporter_defaults[item.id].host) | mandatory ~
-           prometheus_target_strategy_lineinfile_suffix }}'
-    state: present
-  become: true
-  delegate_to: '{{ prometheus_target_host }}'
-  loop: '{{ prometheus_target_exporter +
-         ([] if prometheus_target_skip_default_exporters else prometheus_target_default_exporters) }}'
-  register: lineinfile
-
-- name: Export fact
-  ansible.builtin.set_fact:
-    changed: '{{ changed or lineinfile.changed }}'
diff --git a/tasks/main.yml b/tasks/main.yml
index f8d6caa..5a184f8 100644
--- a/tasks/main.yml
+++ b/tasks/main.yml
@@ -1,11 +1,13 @@
 ---
-- name: Select strategy
+- name: Process all exporters
   ansible.builtin.include_tasks:
-    file: '{{ prometheus_target_strategy }}.yml'
-  vars:
-    changed: false
+    file: process_exporter.yml
+  loop: '{{ prometheus_target_exporter +
+         ([] if prometheus_target_skip_default_exporters else prometheus_target_default_exporters) }}'
+  loop_control:
+    loop_var: item
 
 - name: Run handlers
   ansible.builtin.include_tasks:
     file: handlers.yml
-  when: changed
+  when: changed | default(false)
diff --git a/tasks/process_exporter.yml b/tasks/process_exporter.yml
new file mode 100644
index 0000000..2d13b29
--- /dev/null
+++ b/tasks/process_exporter.yml
@@ -0,0 +1,18 @@
+---
+- name: Set exporter variables
+  vars:
+    _defaults: '{{ prometheus_target_exporter_defaults[item.id] | default({}) if item.id is defined else {} }}'
+  ansible.builtin.set_fact:
+    _target_path: >-
+      {{ (item.path_prefix if item.path_prefix is defined else
+         (_defaults.path_prefix | default(prometheus_target_exporter_target_prefix)))
+         ~
+         (item.path if item.path is defined else _defaults.path) | mandatory }}
+    _target_host: >-
+      {{ (item.host if item.host is defined else _defaults.host) | mandatory }}
+    _target_labels: >-
+      {{ (_defaults.labels | default({})) | combine(item.labels | default({})) }}
+
+- name: Execute strategy
+  ansible.builtin.include_tasks:
+    file: strategy_{{ prometheus_target_strategy }}.yml
diff --git a/tasks/strategy_lineinfile.yml b/tasks/strategy_lineinfile.yml
new file mode 100644
index 0000000..a5dd01f
--- /dev/null
+++ b/tasks/strategy_lineinfile.yml
@@ -0,0 +1,13 @@
+---
+- name: Deploy target via lineinfile
+  ansible.builtin.lineinfile:
+    path: '{{ _target_path }}'
+    line: '{{ prometheus_target_strategy_lineinfile_prefix ~ _target_host ~ prometheus_target_strategy_lineinfile_suffix }}'
+    state: present
+  delegate_to: '{{ prometheus_target_host }}'
+  become: true
+  register: _lineinfile_result
+
+- name: Track changes
+  ansible.builtin.set_fact:
+    changed: '{{ changed | default(false) or _lineinfile_result.changed }}'
diff --git a/tasks/strategy_yaml.yml b/tasks/strategy_yaml.yml
new file mode 100644
index 0000000..1d6df77
--- /dev/null
+++ b/tasks/strategy_yaml.yml
@@ -0,0 +1,71 @@
+---
+- name: Check if target file exists
+  ansible.builtin.stat:
+    path: '{{ _target_path }}'
+  register: _target_file_stat
+  delegate_to: '{{ prometheus_target_host }}'
+
+- name: Read target file
+  ansible.builtin.slurp:
+    src: '{{ _target_path }}'
+  register: _target_file_content
+  delegate_to: '{{ prometheus_target_host }}'
+  when: _target_file_stat.stat.exists
+
+- name: Parse YAML and add host to matching target group
+  ansible.builtin.set_fact:
+    _updated_targets: >-
+      {%- set targets = (_target_file_content.content | b64decode | from_yaml) if _target_file_stat.stat.exists else [] -%}
+      {%- set targets = targets if targets is not none else [] -%}
+      {%- set ns = namespace(found=false, result=[], match=true) -%}
+      {%- for group in targets -%}
+        {%- set group_labels = group.labels | default({}) -%}
+        {%- set ns.match = true -%}
+        {%- if _target_labels | length != group_labels | length -%}
+          {%- set ns.match = false -%}
+        {%- else -%}
+          {%- for key, value in _target_labels.items() -%}
+            {%- if group_labels.get(key) != value -%}
+              {%- set ns.match = false -%}
+            {%- endif -%}
+          {%- endfor -%}
+        {%- endif -%}
+        {%- if ns.match -%}
+          {%- if _target_host not in group.targets -%}
+            {%- set _ = group.targets.append(_target_host) -%}
+          {%- endif -%}
+          {%- set ns.found = true -%}
+          {%- set _ = ns.result.append(group) -%}
+        {%- else -%}
+          {%- set filtered_targets = group.targets | reject('equalto', _target_host) | list -%}
+          {%- if filtered_targets | length > 0 -%}
+            {%- if group_labels | length > 0 -%}
+              {%- set _ = ns.result.append({'labels': group_labels, 'targets': filtered_targets}) -%}
+            {%- else -%}
+              {%- set _ = ns.result.append({'targets': filtered_targets}) -%}
+            {%- endif -%}
+          {%- endif -%}
+        {%- endif -%}
+      {%- endfor -%}
+      {%- if not ns.found -%}
+        {%- if _target_labels | length > 0 -%}
+          {%- set new_group = {'labels': _target_labels, 'targets': [_target_host]} -%}
+        {%- else -%}
+          {%- set new_group = {'targets': [_target_host]} -%}
+        {%- endif -%}
+        {%- set _ = ns.result.append(new_group) -%}
+      {%- endif -%}
+      {{ ns.result }}
+
+- name: Write updated target file
+  ansible.builtin.copy:
+    content: '{{ _updated_targets | to_nice_yaml(indent=2, width=1337) }}'
+    dest: '{{ _target_path }}'
+    mode: '0644'
+  delegate_to: '{{ prometheus_target_host }}'
+  become: true
+  register: _yaml_result
+
+- name: Track changes
+  ansible.builtin.set_fact:
+    changed: '{{ changed | default(false) or _yaml_result.changed }}'