diff --git a/package.json b/package.json
index e7c169f..ef4167f 100644
--- a/package.json
+++ b/package.json
@@ -26,6 +26,7 @@
     "@esbuild-kit/cjs-loader": "^2.4.4",
     "dotenv": "^16.3.1",
     "homeassistant": "^0.2.0",
-    "openai": "^4.12.4"
+    "openai": "^4.12.4",
+    "winston": "^3.11.0"
   }
 }
diff --git a/src/_helpers/ha.ts b/src/_helpers/ha.ts
new file mode 100644
index 0000000..269036f
--- /dev/null
+++ b/src/_helpers/ha.ts
@@ -0,0 +1,62 @@
+/**
+ * Returns an array of entities that match a set of filters
+ * @param {Array} states - An array of state objects.
+ * @param {Array} filters - An array of filter objects, each containing a key and a value.
+ * @param {string} returnProperty - (Optional) A property to return from each entity.
+ * @param {boolean} returnState - (Optional) If true, the state of each entity will be returned in addition to the returnProperty.
+ * @returns {Array} - An array of entities that match the filter criteria.
+ */
+export function getEntities(states, filters = [], returnProperty = null, returnState= false) {
+    if (!Array.isArray(filters)) {
+        throw new Error('Filters must be an array');
+    }
+    if(filters.filter(filter => !filter.key || !filter.value).length > 0) {
+        throw new Error('Filters must contain a key and a value');
+    }
+    let entities = addDomainToEntities(states); 
+    filters.forEach(filter => {
+        entities = entities.filter(entity => {
+            const keys = filter.key.split('.');
+            let value = entity;
+            for (const key of keys) {
+                value = value[key];
+            }
+            return value === filter.value;
+        });
+    });
+    if (returnProperty) {
+        entities = entities.map(entity => {
+            const keys = returnProperty.split('.');
+            let value = entity;
+            for (const key of keys) {
+                value = value[key];
+            }
+            return (returnState) ? `${value} (${entity.state})` : value;
+        });
+    }
+    return entities;
+}
+/**
+ * Adds a domain property to each entity in an array of state objects.
+ * @param {Array} states - An array of state objects.
+ * @returns {Array} - An array of state objects with a domain property added to each entity.
+ */
+export function addDomainToEntities(states) {
+    return states.map(el => {
+        el.domain = el.entity_id.split('.')[0];
+        return el;
+    });
+}
+
+/**
+ * Returns a summary of the state of each entity in an array of state objects.
+ * @param {Array} states - An array of state objects.
+ * @returns {Array} - An array of strings summarizing the state of each entity.
+ */
+export function summarizeEntities(states) {
+    return states.map(el => {
+        const attributes = Object.keys(el.attributes).map(key => { return `${key}: ${el.attributes[key]}`});
+        return `${el.entity_id}: ${el.state} (${attributes.join(', ')})`;
+    });
+}
+
diff --git a/src/_helpers/logs.ts b/src/_helpers/logs.ts
index 690c439..b65ee1c 100644
--- a/src/_helpers/logs.ts
+++ b/src/_helpers/logs.ts
@@ -1,13 +1,19 @@
 
+// TODO: Switch to winston, use ENV_VAR to set log level we want to see
+
 /**
  * Log a message to the console with proper formatting
  */
-
 export async function log(category, severity, ...messages) {
+
+    //if(severity === 'debug') { return null; }
     const emojiForCategory = {
         'openai': '🧠',
         'ha': '🏠',
         'app': '🤖',
+        'prompt': '🗣️',
+        'response': '📢',
     }
-    return console.log(emojiForCategory[category], `[${category.toUpperCase()}]`, ...messages);
+    const emoji = emojiForCategory[category] || '';
+    return console.log(emoji, `[${category.toUpperCase()}]`, ...messages);
 }
\ No newline at end of file
diff --git a/src/_helpers/openai.ts b/src/_helpers/openai.ts
new file mode 100644
index 0000000..975ebed
--- /dev/null
+++ b/src/_helpers/openai.ts
@@ -0,0 +1,43 @@
+import {
+    LANGUAGE,
+    OPENAI_MODEL,
+} from '../config';
+import {log} from './logs';
+
+/**
+ * Get the first chat response from OpenAI API
+ * @param {Object} openai - OpenAI API instance
+ * @param {string} prompt - Prompt to send to the API
+ * @param {Object} paramOptions - Options for the prompt
+ * @returns {Promise<Object>} - Promise that resolves to the chat completion object
+ */
+
+export async function getFirstChatResponse(openai, prompt, paramOptions ) {
+    if(!openai) {
+        throw new Error('OpenAI must be initialized');
+    }
+    if(!prompt) {
+        throw new Error('Prompt must be a string');
+    }
+    const defaultOptions = {
+        model: OPENAI_MODEL,
+    }
+    const options = {
+        ...defaultOptions,
+        ...paramOptions,
+    }
+    log('prompt','debug',prompt);
+    const chatCompletion = await openai.chat.completions.create({
+        messages: [
+            { role: 'user', content: prompt },
+            {role: 'user', content: `Respond in ${LANGUAGE}`}
+        ],
+        ...options,
+      });
+    if(chatCompletion.choices.length > 0 && chatCompletion.choices[0].message) {
+        log('response','info',chatCompletion.choices[0].message.content);
+        return chatCompletion.choices[0].message.content;
+    }
+    log(prompt, 'warn', 'No response from OpenAI API for prompt', prompt);
+    return null;
+}
\ No newline at end of file
diff --git a/src/_helpers/sleep.ts b/src/_helpers/sleep.ts
new file mode 100644
index 0000000..cb192d8
--- /dev/null
+++ b/src/_helpers/sleep.ts
@@ -0,0 +1,7 @@
+/**
+ * Sleep for a given number of milliseconds.
+ * @param ms - The number of milliseconds to sleep for.
+ */
+export async function sleep(ms) { 
+    return new Promise(resolve => setTimeout(resolve, ms));
+}
\ No newline at end of file
diff --git a/src/_tests/ha.test.ts b/src/_tests/ha.test.ts
new file mode 100644
index 0000000..a5182c9
--- /dev/null
+++ b/src/_tests/ha.test.ts
@@ -0,0 +1,84 @@
+import {getEntities, addDomainToEntities, summarizeEntities} from '../_helpers/ha';
+
+const mockStates = [
+  { entity_id: 'binary_sensor.entry_door', attributes: { device_class: 'door'}, state: 'off' },
+  { entity_id: 'binary_sensor.front_door', attributes: { device_class: 'door'}, state: 'on' },
+  { entity_id: 'binary_sensor.living_window', attributes: { device_class: 'window'}, state: 'off' },
+  { entity_id: 'light.living', state: 'off', attributes: {} },
+  { entity_id: 'light.living', state: 'on', attributes: {}},
+];  
+
+describe('getEntities', () => {
+  it('should return all entities if no filter is applied', () => {
+    const result = getEntities(mockStates);
+    expect(result).toEqual(mockStates);
+  });
+
+  it('should return an array of entities for a specific domain', () => {
+    const result = getEntities(mockStates, [{key: 'domain', value: 'binary_sensor'}], 'entity_id');
+    expect(result).toEqual([
+      'binary_sensor.entry_door',
+      'binary_sensor.front_door',
+      'binary_sensor.living_window',
+    ]);
+  });
+  it('should return an array of entities for a specific domain with their state', () => {
+    const result = getEntities(mockStates, [{key: 'domain', value: 'binary_sensor'}], 'entity_id', true);
+    expect(result).toEqual([
+      'binary_sensor.entry_door (off)',
+      'binary_sensor.front_door (on)',
+      'binary_sensor.living_window (off)',
+    ]);
+  });
+
+  it('should return an array of entities with a specific state', () => {
+    const result = getEntities(mockStates, [{key: 'state', value: 'on'}], 'entity_id');
+    expect(result).toEqual([
+      'binary_sensor.front_door',
+      'light.living',
+    ]);
+  });
+
+  it('should return an array of entities with a specific device_class', () => {
+    const result = getEntities(mockStates, [{key: 'attributes.device_class', value: 'door'}], 'entity_id');
+    expect(result).toEqual([
+      'binary_sensor.entry_door',
+      'binary_sensor.front_door',
+    ]);
+  });
+
+  it('should return an array of entities with a specific device_class and state', () => {
+    const result = getEntities(mockStates, [ {key: 'attributes.device_class', value: 'door'}, {key: 'state', value: 'on'}], 'entity_id');
+    expect(result).toEqual([
+      'binary_sensor.front_door',
+    ]);
+  });
+});
+
+describe('addDomainToEntities', () => {
+  it('should add domain property to each entity', () => {
+    const states = [
+      { entity_id: 'light.living_room', state: 'on', attributes: {} },
+      { entity_id: 'switch.kitchen', state: 'off', attributes: {} },
+    ];
+    const expected = [
+      { entity_id: 'light.living_room', state: 'on', attributes: {}, domain: 'light' },
+      { entity_id: 'switch.kitchen', state: 'off', attributes: {}, domain: 'switch' },
+    ];
+    expect(addDomainToEntities(states)).toEqual(expected);
+  });
+});
+
+describe('summarizeEntities', () => {
+  it('should return an array of strings summarizing the state of each entity', () => {
+    const states = [
+      { entity_id: 'light.living_room', state: 'on', attributes: {} },
+      { entity_id: 'switch.kitchen', state: 'off', attributes: {friendly_name: 'Kitchen Switch'} },
+    ];
+    const expected = [
+      'light.living_room: on ()',
+      'switch.kitchen: off (friendly_name: Kitchen Switch)',
+    ];
+    expect(summarizeEntities(states)).toEqual(expected);
+  });
+});
\ No newline at end of file
diff --git a/src/config.ts b/src/config.ts
index ec7aac0..45108d8 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -6,6 +6,7 @@ export const {
 const DEFAULT_HOME_ASSISTANT_HOST = (NODE_ENV === 'production') ? 'http://supervisor/core' : 'http://homeassistant.local';
 const DEFAULT_HOME_ASSISTANT_PORT = (NODE_ENV === 'production') ? 80 : 8123;
 const DEFAULT_HOME_ASSISTANT_TOKEN = process.env.SUPERVISOR_TOKEN;
+const DEFAULT_UPDATE_INTERVAL = (NODE_ENV === 'production') ? 1000*60*60 : 5000; // Every hour in production, every 5 seconds in dev
 
 // =====================================================================================================================
 // Config
@@ -14,7 +15,17 @@ const DEFAULT_HOME_ASSISTANT_TOKEN = process.env.SUPERVISOR_TOKEN;
 
 export const {
     OPENAI_TOKEN, 
+    OPENAI_MODEL = 'gpt-3.5-turbo',
+    
     HOME_ASSISTANT_HOST = DEFAULT_HOME_ASSISTANT_HOST,
     HOME_ASSISTANT_PORT = DEFAULT_HOME_ASSISTANT_PORT,
     HOME_ASSISTANT_TOKEN = DEFAULT_HOME_ASSISTANT_TOKEN,
-} = process.env;
\ No newline at end of file
+
+
+    UPDATE_INTERVAL = DEFAULT_UPDATE_INTERVAL,
+    LANGUAGE = 'french'
+
+} = process.env;
+
+export const SUMMARY_DEVICE_ENTITY_PREFIX = 'summary_device_'; // will be followed by the device name
+export const SUMMARY_DEVICES_ENTITIES = ['hall_tablet','iphone_thomas','iphone_caroline','macbookpro_thomas','roborock','octoprint','litterbox','toothbrush'];
\ No newline at end of file
diff --git a/src/index.ts b/src/index.ts
index d56b0a5..707b8bb 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,18 +1,43 @@
 import 'dotenv/config';
-import {init}  from './init';
+
 import {log} from './_helpers/logs';
+import {sleep} from './_helpers/sleep';
 
+import {
+  SUMMARY_DEVICES_ENTITIES,
+  UPDATE_INTERVAL,
+} from './config';
+import {init}  from './init';
+import {updateDeviceSummary} from './summary'
 
 async function main() {
 
   // Init
   // ===================================================================================================================
   log('app','info','Starting up...');
-  log('app','info','Here are your environment variables:');
-  log('app','info',process.env);
-
   const {ha, openai } = await init();
   log('app','info','Initialized.');
+
+
+  // Jobs
+  // ===================================================================================================================
+  const states = await ha.states.list();
+
+  while(true) {
+
+    // Device Summaries
+    // ===================================================================================================================
+    log('app','info',`Updating summary for ${SUMMARY_DEVICES_ENTITIES.length} devices...`);
+    await Promise.allSettled(SUMMARY_DEVICES_ENTITIES.map(device => updateDeviceSummary(openai, ha, states, device)));
+    log('app','info',`Summary updated for ${SUMMARY_DEVICES_ENTITIES.length} devices.`);
+
+    // Sleep till next run
+    // ===================================================================================================================
+    // TODO: Implement publish/subscribe pattern to avoid polling
+    log('app','info',`Sleeping for ${UPDATE_INTERVAL/1000} seconds...`);
+    await sleep(UPDATE_INTERVAL);
+
+  }
 }
 
 main();
\ No newline at end of file
diff --git a/src/summary.ts b/src/summary.ts
new file mode 100644
index 0000000..2d58aa3
--- /dev/null
+++ b/src/summary.ts
@@ -0,0 +1,94 @@
+import 'dotenv/config';
+import {summarizeEntities} from './_helpers/ha';
+import {getFirstChatResponse} from './_helpers/openai';
+import {log} from './_helpers/logs';
+import {SUMMARY_DEVICE_ENTITY_PREFIX} from './config';
+
+/**
+ * Get a prompt for summarizing the state of a device
+ * @param {Array} states - List of states of all entities
+ * @param {string} deviceName - Name of the device to summarize
+ * @param {Object} paramOptions - Options for the prompt
+ * @param {number} paramOptions.length - Maximum length of the prompt
+ * @param {string} paramOptions.customPrompt - Custom prompt to add to the briefing
+ * @returns {string} - Prompt for summarizing the state of the device
+ */
+export function getPromptForDeviceSummary(states, deviceName, paramOptions) {
+    if(!states || states.length === 0) {
+        throw new Error('States must be an array');
+    }
+    const deviceEntities = states.filter(el => el.entity_id.includes(deviceName));
+    if(deviceEntities.length === 0) {
+        log('app','warn',`No entity found for device ${deviceName}`);
+        return null;
+    }
+    const summary = summarizeEntities(deviceEntities);
+    const defaultOptions = {
+        length: 200,
+        customPrompt: '',    
+    }
+    const options = {
+        ...defaultOptions,
+        ...paramOptions,
+    }
+
+    let prompt = [];
+    const briefing = `
+    Following is an overview of the state of a device.
+    Summarize it in less than ${options.length} characters.
+    Do not start nor include the name of the device. Do not start by "summary" or "briefing" or "device".
+    Only keep the most important information, do not give everything you have. ALWAYS keep it short. 
+    Prioritize errors, last state changes, and then only the rest.
+    Write a single sentence, as if your were  do not use bullets point, separator, line breaks.
+    Ignore device containing "summary" or "briefing" or "device" in their name.
+    ${options.customPrompt}
+    `;
+    prompt.push(briefing);
+    prompt = [...prompt, ...summary];
+    return prompt.join('\n');
+}
+
+/**
+ * Get a summary of the state of a device
+ * @param {Object} openai - OpenAI API instance
+ * @param {Object} ha - Home Assistant instance
+ * @param {Array} states - List of states of all entities
+ * @param {string} deviceName - Name of the device to summarize
+ * @param {Object} paramOptions - Options for the prompt
+ * @param {number} paramOptions.length - Maximum length of the prompt
+ * @param {string} paramOptions.customPrompt - Custom prompt to add to the briefing
+ * @returns {Promise<string>} - Promise that resolves to a summary of the state of the device
+ */
+export async function getDeviceSummary(openai, ha, states, deviceName, paramOptions) {
+    const prompt = getPromptForDeviceSummary(states, deviceName, paramOptions);
+    if(!prompt) {
+        return null;
+    }
+    const summary = getFirstChatResponse(openai, prompt);
+    return summary;
+}
+
+/**
+ * Update the summary of the state of a device
+ * @param {Object} openai - OpenAI API instance
+ * @param {Object} ha - Home Assistant instance
+ * @param {Array} states - List of states of all entities
+ * @param {string} deviceName - Name of the device to summarize
+ * @param {Object} paramOptions - Options for the prompt
+ * @param {number} paramOptions.length - Maximum length of the prompt
+ * @param {string} paramOptions.customPrompt - Custom prompt to add to the briefing
+ * @returns {Promise<Object>} - Promise that resolves to the updated summary entity
+ */
+export async function updateDeviceSummary(openai, ha, states, deviceName, paramOptions) {
+    const summary = await getDeviceSummary(openai, ha, states, deviceName, paramOptions);
+    if(!summary) {
+        return null;
+    }
+    return ha.states.update('sensor', `${SUMMARY_DEVICE_ENTITY_PREFIX}${deviceName}`, {
+        state: 1,
+        attributes: {
+          content: summary,
+          last_updated: new Date().toISOString(),
+        }
+      });
+}
\ No newline at end of file