Service layer and list tags from GitHub

**Changes:**

* Install and use command business logic is near complete
* Request for a list of tags from GitHub is now working
* Clean abstraction of install vs use

Author: morgan-wowk

src/app/bootstrap.py

@@ -42,4 +42,4 @@ def run():
     args = parser.parse_args()
 
     command = get_command_by_name(args.command)
-    command.exec()
+    command.exec(args)

src/app/commands/command.py

@@ -1,10 +1,10 @@
 from abc import ABC, abstractmethod
-from argparse import Action
+from argparse import Action, Namespace
 
 
 class Command(ABC):
     @abstractmethod
-    def exec(self) -> None:
+    def exec(self, args: Namespace) -> None:
         pass
 
     @staticmethod

src/app/commands/install_command.py

@@ -1,14 +1,21 @@
-from argparse import Action
+from argparse import Action, Namespace
 
 from src.app.commands.command import Command
+from src.app.services.composer_service import ComposerService
+from src.app.services.github_service import GitHubService
 
 
 class InstallCommand(Command):
     NAME = 'install'
     DESCRIPTION = 'Install a version of Composer without using it.'
 
-    def exec(self):
-        print("Install command executed.")
+    def exec(self, args: Namespace):
+        desired_version = args.version[0]
+
+        github_service = GitHubService('composer', 'composer')
+        composer_service = ComposerService(github_service)
+
+        composer_service.install_version(desired_version)
 
     @staticmethod
     def define_signature(parser: Action):

src/app/commands/scan_command.py

@@ -1,4 +1,4 @@
-from argparse import Action
+from argparse import Action, Namespace
 
 from src.app.commands.command import Command
 
@@ -7,8 +7,9 @@ class ScanCommand(Command):
     NAME = 'scan'
     DESCRIPTION = 'Use .cvm_config from the current directory if present.'
 
-    def exec(self):
+    def exec(self, args: Namespace):
         print("Scan command executed.")
+        print(args)
 
     @staticmethod
     def define_signature(parser: Action):

src/app/commands/use_command.py

@@ -1,14 +1,25 @@
-from argparse import Action
+from argparse import Action, Namespace
 
 from src.app.commands.command import Command
+from src.app.services.composer_service import ComposerService
+from src.app.services.github_service import GitHubService
 
 
 class UseCommand(Command):
     NAME = 'use'
-    DESCRIPTION = 'Use a specific version of Composer. Defaulting to the latest-\nstable version when there is a lack of specificity.\n\n'
+    DESCRIPTION = 'Use a specific version of Composer. Defaulting to the latest-\nstable version when there is a ' \
+                  'lack of specificity.\n\n '
 
-    def exec(self):
-        print("Use command executed.")
+    def exec(self, args: Namespace):
+        desired_version = args.version[0]
+
+        github_service = GitHubService('composer', 'composer')
+        composer_service = ComposerService(github_service)
+
+        existed = composer_service.use_version(desired_version)
+        if not existed:
+            composer_service.install_version(desired_version)
+            composer_service.use_version(desired_version, False)
 
     @staticmethod
     def define_signature(parser: Action):

src/app/services/composer_service.py

@@ -0,0 +1,46 @@
+import sys
+
+from src.app.services.github_service import GitHubService
+import logging
+
+
+class ComposerService:
+    def __init__(self, github_service: GitHubService):
+        self.github_service = github_service
+        self.tags = None
+
+    def list_tags(self):
+        if self.tags is None:
+            self.tags = self.github_service.list_tags()
+
+        return self.tags
+
+    def tag_exists(self, desired_tag: str) -> bool:
+        github_tags = self.list_tags()
+
+        for tag_object in github_tags:
+            if tag_object.get('name') == desired_tag:
+                return True
+
+        return False
+
+    def cache_exists(self, tag_name: str) -> bool:
+
+        return True
+
+    def install_version(self, tag_name: str) -> bool:
+        if not self.tag_exists(tag_name):
+            logging.error("Tag {} does not exist.".format(tag_name))
+            sys.exit(1)
+
+        # TODO: Download version into cache directory
+
+        return True
+
+    def use_version(self, tag_name: str, check_exists: bool = True) -> bool:
+        if check_exists and not self.cache_exists(tag_name):
+            return False
+
+        # TODO: Use cached version if exists
+
+        return True

src/app/services/github_service.py

@@ -0,0 +1,25 @@
+import logging
+import sys
+
+import requests
+
+
+class GitHubService:
+    def __init__(self, owner_id: str, repo_id: str):
+        self.owner_id = owner_id
+        self.repo_id = repo_id
+
+    def list_tags(self) -> requests.Response:
+        headers = {'Accept': 'application/vnd.github.v3+json'}
+        r = requests.get(
+            "https://api.github.com/repos/{}/{}/tags".format(self.owner_id, self.repo_id),
+            headers=headers
+        )
+
+        if r.status_code >= 400:
+            logging.error('Failed to fetch available tags from GitHub.')
+            sys.exit(1)
+
+        json = r.json()
+
+        return json

src/requirements.txt

@@ -1,8 +1,13 @@
 ansicolors==1.1.8
 argparse-color-formatter==1.2.2.post2
+certifi==2020.12.5
+chardet==4.0.0
 colorama==0.4.4
+idna==2.10
 mypy==0.790
 mypy-extensions==0.4.3
+requests==2.25.1
 six==1.15.0
 typed-ast==1.4.2
 typing-extensions==3.7.4.3
+urllib3==1.26.2