chore(python): implement logic for accessing PostgreSQL and make a simplest GET query work

Part of #16
Relate to #15

Author: php-coder

README.md

@@ -48,14 +48,14 @@ Generates the endpoints (or a whole app) from a mapping (SQL query -> URL)
    | -----------| ----------------------------| ---------------------------| --------- |
    | JavaScript | `npx query2app --lang js`   | [`app.js`](examples/js/app.js)<br/>[`routes.js`](examples/js/routes.js)<br/>[`package.json`](examples/js/package.json) | Web: [`express`](https://www.npmjs.com/package/express), [`body-parser`](https://www.npmjs.com/package/body-parser)<br>Database: [`mysql`](https://www.npmjs.com/package/mysql) |
    | Golang     | `npx query2app --lang go`   | [`app.go`](examples/go/app.go)<br/>[`routes.go`](examples/go/routes.go)<br/>[`go.mod`](examples/go/go.mod) | Web: [`go-chi/chi`](https://github.com/go-chi/chi)<br/>Database: [`go-sql-driver/mysql`](https://github.com/go-sql-driver/mysql), [`jmoiron/sqlx`](https://github.com/jmoiron/sqlx) |
-   | Python     | `npx query2app --lang python` | [`app.py`](examples/python/app.py)<br/>[`routes.py`](examples/python/routes.py)<br/>[`requirements.txt`](examples/python/requirements.txt) | Web: [FastAPI](https://github.com/tiangolo/fastapi), [Uvicorn](https://www.uvicorn.org) |
+   | Python     | `npx query2app --lang python` | [`app.py`](examples/python/app.py)<br/>[`routes.py`](examples/python/routes.py)<br/>[`requirements.txt`](examples/python/requirements.txt) | Web: [FastAPI](https://github.com/tiangolo/fastapi), [Uvicorn](https://www.uvicorn.org)<br/>Database: [](https://pypi.org/project/psycopg2/) |
 
 1. Run the application
    | Language   | Commands to run the application |
    | -----------| --------------------------------|
    | JavaScript | <pre>$ npm install<br/>$ export DB_NAME=my-db DB_USER=my-user DB_PASSWORD=my-password<br/>$ npm start</pre> |
    | Golang     | <pre>$ go run *.go</pre>or<pre>$ go build -o app<br/>$ ./app</pre> |
-   | Python     | <pre>$ pip install -r requirements.txt<br/>$ uvicorn app:app</pre> |
+   | Python     | <pre>$ pip install -r requirements.txt<br/>$ export DB_NAME=my-db DB_USER=my-user DB_PASSWORD=my-password<br/>$ uvicorn app:app</pre> |
 
    ---
    :bulb: **NOTE**

examples/python/requirements.txt

@@ -1,2 +1,3 @@
 fastapi===0.83.0
 uvicorn==0.18.3
+psycopg2-binary==2.9.3

examples/python/routes.py

@@ -1,15 +1,42 @@
+import os
+import psycopg2
+
 from fastapi import APIRouter
 
 router = APIRouter()
 
 
 @router.get('/v1/categories/count')
 def get_v1_categories_count():
-    pass
+    conn = psycopg2.connect(
+        database = os.getenv('DB_NAME'),
+        user = os.getenv('DB_USER'),
+        password = os.getenv('DB_PASSWORD'),
+        host = os.getenv('DB_HOST', 'localhost'),
+        port = 5432)
+    try:
+        with conn:
+            with conn.cursor() as cur:
+                cur.execute('SELECT COUNT(*) AS counter FROM categories')
+                return cur.fetchone()[0]
+    finally:
+        conn.close()
 
 @router.get('/v1/collections/:collectionId/categories/count')
 def get_v1_collections_collection_id_categories_count():
-    pass
+    conn = psycopg2.connect(
+        database = os.getenv('DB_NAME'),
+        user = os.getenv('DB_USER'),
+        password = os.getenv('DB_PASSWORD'),
+        host = os.getenv('DB_HOST', 'localhost'),
+        port = 5432)
+    try:
+        with conn:
+            with conn.cursor() as cur:
+                cur.execute('SELECT COUNT(DISTINCT s.category_id) AS counter FROM collections_series cs JOIN series s ON s.id = cs.series_id WHERE cs.collection_id = :collectionId')
+                return cur.fetchone()[0]
+    finally:
+        conn.close()
 
 @router.get('/v1/categories')
 def get_list_v1_categories():
@@ -21,7 +48,19 @@ def post_v1_categories():
 
 @router.get('/v1/categories/:categoryId')
 def get_v1_categories_category_id():
-    pass
+    conn = psycopg2.connect(
+        database = os.getenv('DB_NAME'),
+        user = os.getenv('DB_USER'),
+        password = os.getenv('DB_PASSWORD'),
+        host = os.getenv('DB_HOST', 'localhost'),
+        port = 5432)
+    try:
+        with conn:
+            with conn.cursor() as cur:
+                cur.execute('SELECT id , name , name_ru , slug FROM categories WHERE id = :categoryId')
+                return cur.fetchone()[0]
+    finally:
+        conn.close()
 
 @router.put('/v1/categories/:categoryId')
 def put_v1_categories_category_id():

src/templates/requirements.txt.ejs

@@ -1,2 +1,3 @@
 fastapi===0.83.0
 uvicorn==0.18.3
+psycopg2-binary==2.9.3

src/templates/routes.py.ejs

@@ -1,3 +1,6 @@
+import os
+import psycopg2
+
 from fastapi import APIRouter
 
 router = APIRouter()
@@ -14,14 +17,32 @@ endpoints.forEach(function(endpoint) {
 
     endpoint.methods.forEach(function(method) {
         const pythonMethodName = generate_method_name(method.name, path)
+        const sql = formatQuery(method.query)
 
         if (method.name === 'get' || method.name === 'get_list') {
 %>
 @router.get('<%- path %>')
 def <%- pythonMethodName %>():
+<%          if (method.name === 'get') { -%>
+    conn = psycopg2.connect(
+        database = os.getenv('DB_NAME'),
+        user = os.getenv('DB_USER'),
+        password = os.getenv('DB_PASSWORD'),
+        host = os.getenv('DB_HOST', 'localhost'),
+        port = 5432)
+    try:
+        with conn:
+            with conn.cursor() as cur:
+                cur.execute('<%- sql %>')
+                return cur.fetchone()[0]
+    finally:
+        conn.close()
+<%
+            } else {
+-%>
     pass
 <%
-
+            }
         }
         if (method.name === 'post') {
 %>