userctx.py

#!/usr/bin/env python3
import os, sys, subprocess, tomllib, argparse

COMMAND_LIST = 'list'
COMMAND_APPLY = 'apply'
COMMAND_CTX_NAME = 'context_name'
COMMANDS_ALL = [COMMAND_LIST, COMMAND_APPLY]

SECTION_GENERAL = 'general'
KEY_APPS = 'apps'
KEY_DRY_RUN = 'dry_run'

SECTION_APPS = 'apps'
KEY_SRC_PATH = 'source_path'
KEY_DST_PATH = 'target_path'
KEY_RELOAD = 'reload'
KEY_ACTIONS = 'actions'
KEY_SYMLINK = 'symlink'
KEY_SCRIPT = 'script'
KEY_EXEC = 'exec'
ACTIONS_ALL = [KEY_SYMLINK, KEY_SCRIPT, KEY_EXEC, KEY_RELOAD]
APPS_VALID_KEYS = [KEY_ACTIONS, KEY_SYMLINK, KEY_SCRIPT, KEY_EXEC, KEY_RELOAD, KEY_SRC_PATH, KEY_DST_PATH]

ENV_CONTEXT_NAME = 'CONTEXT_NAME'
ENV_CONTEXT_SRC = 'CONTEXT_SRC'
ENV_CONTEXT_DST = 'CONTEXT_DST'

APP_NAME = os.path.basename(sys.argv[0])
APP_DESC = 'A simple configuration switcher for various usage scenarios.'
HOME = os.path.expanduser('~')
XDG_CONFIG_HOME = os.getenv('XDG_CONFIG_HOME', os.path.join(HOME, '.config'))

class OS(object):
    def __init__(self, chdir='', env=None):
        self.shell = os.getenv('SHELL') or 'bash'
        if env: env.update(os.environ)
        self.env = env
    
    def exec_command(self, command: list[str], quiet=False) -> int:
        return subprocess.run(command, capture_output=quiet, env=self.env).returncode

    def exec_script(self, path: str) -> None:
        return self.exec_command([self.shell, path])

    def exec_snippet(self, code: str) -> None:
        return self.exec_command([self.shell, "-c", code])
        
    def scan_dir(self, path: str) -> list[str]:
        out = []
        def scan(dir: str, prefix: str):
            entries = list(os.scandir(dir)) # extract values from iterator
            out.extend([os.path.join(prefix, e.name) for e in entries if e.is_file()])
            for d in [e.name for e in entries if e.is_dir()]:
                scan(os.path.join(dir, d), os.path.join(prefix, d))
        scan(path, '')
        return out


class Task(object):
    def __init__(self, name: str, src: str, dst: str, conf: dict, dry_run=True):
        self.name = name
        self.src = conf.get(KEY_SRC_PATH) or src # default is ~/.config/userctx/<context>/<task>
        self.dst = conf.get(KEY_DST_PATH) or dst # default is ~/.config/<task>
        self.symlinks = conf.get(KEY_SYMLINK)
        self.scripts = conf.get(KEY_SCRIPT)
        self.code = conf.get(KEY_EXEC)
        self.reload = conf.get(KEY_RELOAD)
        self.actions = conf.get(KEY_ACTIONS)
        if self.actions is None: # not set, actions = [] is a no-op conf for app
            self.actions = [KEY_SYMLINK]
            if self.scripts is not None: # may be an empty array
                self.actions.append(KEY_SCRIPT)
            if self.code is not None:
                self.actions.append(KEY_EXEC)
            if self.reload is not None:
                self.actions.append(KEY_RELOAD)
        self.shell = OS(env={ENV_CONTEXT_NAME: self.name, ENV_CONTEXT_SRC: self.src, ENV_CONTEXT_DST: self.dst})
        self.dry_run = dry_run
        
    def execute(self) -> None:
        if self.dry_run:
            print("Configured actions:", self.actions)
        for a in self.actions:
            if a == KEY_SYMLINK:
                self._symlink()
            elif a == KEY_SCRIPT:
                self._run_scripts()
            elif a == KEY_EXEC:
                self._run_code(self.code)
            elif a == KEY_RELOAD:
                self._run_code(self.reload)

    def _symlink(self) -> None:
        entries = self.shell.scan_dir(self.src)
        if not entries:
            return
        if self.symlinks is None: # will symlink everything we have then
            self.symlinks = {'*': '*'}
        not_included = [e for e in entries if e not in self.symlinks]

        if '*' in self.symlinks:
            target = self.symlinks['*']
            if target == '*': # symlink."*" = "*" in config
                self.symlinks.update(dict(zip(not_included, not_included)))
            else: # symlink."*" = "some/path/target.file"
                self.symlinks[not_included[0]] = target
            del self.symlinks['*']

        for k, v in self.symlinks.items():
            src, dst = os.path.join(self.src, k), os.path.join(self.dst, v)
            if self.dry_run:
                print("will remove:", dst)
                print("will symlink:", src, "to", dst)
                continue
            if os.path.lexists(dst): os.remove(dst)
            os.symlink(src, dst)

    def _run_scripts(self) -> None:
        if not self.scripts: # nothing provided explicitly
            self.scripts = [e for e in self.shell.scan_dir(self.src) if e.endswith('.sh')]
        if self.dry_run:
            print(f'will execute scripts from {self.src}:', self.scripts)
            return
        for s in self.scripts:
            self.shell.exec_script(os.path.join(self.src, s))

    def _run_code(self, snippet: str) -> None:
        if self.dry_run:
            print("will execute script:", snippet)
            return
        self.shell.exec_snippet(snippet)

class ContextManagerConfig(object):
    def __init__(self, conf_file_path: str, dry_run: bool):
        try:
            with open(conf_file_path, 'rb') as f: self.config = tomllib.load(f)
        except Exception as e:
            raise ValueError('error parsing "{config_file_path}":', e)

        def is_arr_of_str(x) -> bool:
            return isinstance(x, list) and all(isinstance(s, str) for s in x)

        def is_dict_of_str(x) -> bool:
            return isinstance(x, dict) and all(isinstance(k, str) and isinstance(v, str) for k, v in x.items())

        def user_path(s: str) -> str:
            return os.path.expanduser(s)

        if SECTION_GENERAL not in self.config or not isinstance(self.config[SECTION_GENERAL], dict):
            raise ValueError(f'section "{SECTION_GENERAL}" must be present in the config and must be a valid mapping (table)')

        # Will extensively check what's inside config.toml without additinal imports.
        # Also, fuck dynamic typing!
        self.tasks = self.config[SECTION_GENERAL].get(KEY_APPS)
        if not self.tasks or not is_arr_of_str(self.tasks):
            raise ValueError(f'invalid config: key "{KEY_APPS}" in section "{SECTION_GENERAL}" must be a non-empty array of strings')

        errors, err_count = list(), 0 # fuck it again
        self.dry_run = (self.config[SECTION_GENERAL].get(KEY_DRY_RUN) or False) or dry_run
        if not isinstance(self.dry_run, bool):
            err_count += 1
            errors.append(f'{err_count}. key "{KEY_DRY_RUN}" in section "{SECTION_GENERAL} of the config must be bool"')
        
        self.home = user_path(self.config[SECTION_GENERAL].get(KEY_SRC_PATH) or os.path.join(XDG_CONFIG_HOME, 'userctx'))
        if not os.path.isabs(self.home):
            err_count += 1
            errors.append(f'{err_count}. path "{self.home}" in key "{KEY_SRC_PATH}" of section "{SECTION_GENERAL}" must be absolute or relative to home: "~/{self.home}"')

        self.managed_path = user_path(self.config[SECTION_GENERAL].get(KEY_DST_PATH) or XDG_CONFIG_HOME)
        if not os.path.isabs(self.managed_path):
            err_count += 1
            errors.append(f'{err_count}. path "{self.managed_path}" in key "{KEY_DST_PATH}" of section "{SECTION_GENERAL}" must be absolute or relative to home: "~/{self.managed_path}"')
        
        if SECTION_APPS not in self.config: # valid case with all defaults
            self.config[SECTION_APPS] = dict()

        tasks = self.config.get(SECTION_APPS)
        for name, t in tasks.items():
            errstr = f'for app "{name}"' 
            for k in list(t.keys()): # we might change t
                v = t[k]
                if k not in APPS_VALID_KEYS:
                    err_count += 1
                    errors.append(f'{err_count}. {errstr} unknown key "{k}"')
                    continue
                if k == KEY_EXEC and not isinstance(v, str):
                    err_count += 1
                    errors.append(f'{err_count}. {errstr} key "{k}" must be a string') 
                elif k == KEY_SYMLINK and not is_dict_of_str(v):
                    err_count += 1
                    errors.append(f'{err_count}. {errstr} key "{k}" must be a table (mapping)')
                elif k in [KEY_SCRIPT, KEY_ACTIONS] and not is_arr_of_str(v):
                    err_count += 1
                    errors.append(f'{err_count}. {errstr} key "{k}" must be array of strings')
                elif k == KEY_ACTIONS and not all(a in ACTIONS_ALL for a in v):
                    err_count += 1
                    errors.append(f'{err_count}. {errstr} invalid actions found: {[a for a in v if a not in ACTIONS_ALL]} in key "{k}", valid actions are: {ACTIONS_ALL}')
                elif k == KEY_RELOAD and not isinstance(v, str):
                    err_count += 1
                    errors.append(f'{err_count}. {errstr} "{KEY_RELOAD}" must ba a string')
                elif k in [KEY_SRC_PATH, KEY_DST_PATH] and not isinstance(v, str):
                    err_count += 1
                    errors.append(f'{err_count}. {errstr}  key "{k}" must contain a string')  
                elif k in [KEY_SRC_PATH, KEY_DST_PATH]: 
                    p = user_path(v)
                    if not os.path.isabs(p):
                        err_count += 1
                        errors.append(f'{err_count}. {errstr} path "{v}" in key "{k}" must be either absolute or relative to home: "~/{v}"')
                    t[k] = p # substituting path (e.g. "~/somedir" -> "/home/user/somedir")
        if errors:
            print(f'{err_count} errors found in the config "{conf_file_path}":', file=sys.stderr)
            print('\n'.join(errors), file=sys.stderr)
            raise ValueError('invalid config')

    def get_contexts_list(self) -> list[str]:
        return [entry.name for entry in os.scandir(self.home) if entry.is_dir()]

    def get_tasks_for_context(self, context_name: str) -> list[Task]:
        ctx_path = os.path.join(self.home, context_name)
        if not (os.path.exists(ctx_path) and os.path.isdir(ctx_path)): 
            raise ValueError(f'context directory "{context_name}" not found in "{self.home}"')
        out = list()
        for name in self.tasks:
            src_path = os.path.join(ctx_path, name) 
            dst_path = os.path.join(self.managed_path, name)
            t = Task(name, src_path, dst_path, self.config[SECTION_APPS].get(name) or dict(), dry_run=self.dry_run) 
            out.append(t)
        return out


class ContextManager(object):
    def __init__(self, config: ContextManagerConfig):
        self.config = config

    def list_contexts(self) -> None:
        print('\n'.join(self.config.get_contexts_list()))

    def apply_context(self, context_name: str) -> None:
        print(f'loading and applying context: "{context_name}"')
        try:
            tasks = self.config.get_tasks_for_context(context_name)
        except Exception as e:
            print(f'error getting tasks for context "{context_name}":', e)
            return 
        if not tasks:
            print(f'no tasks found for context "{context_name}"')
            return
        errors = list()
        for task in tasks:
            print(f'running task "{task.name}"...', end=' ')
            try:
                task.execute()
                print("OK")
            except Exception as e:
                errors.append((task.name, e))
                print('FAILED')
        if errors:
            print('Errors:')
            for t in errors:
                print(f'task: "{t[0]}", error: "{t[1]}"')


class Runner(object):
    def run(self) -> int:
        p = argparse.ArgumentParser(prog=APP_NAME, description=APP_DESC)
        p.add_argument('-c', '--config', help='path to config file, default: %(default)s',
                       default=os.path.join(XDG_CONFIG_HOME, 'userctx', 'config.toml'))
        p.add_argument('-n', '--nop', action='store_true', default=False, 
                       help='do nothing, just print out what userctx will do')
        subp = p.add_subparsers(help='command to execute', dest='command')
        applyp = subp.add_parser(COMMAND_APPLY, help='load context (provide name of context)')
        applyp.add_argument(COMMAND_CTX_NAME, help='name of context to load')
        listp = subp.add_parser(COMMAND_LIST, help='list available contexts')
        try: # just in case
            args = p.parse_args()
        except Exception as e:
            print("error parsing command-line arguments:", e, file=sys.stderr)
            return 1
        try:
            config = ContextManagerConfig(args.config, args.nop)
        except Exception as e:
            print("error loading config:", e, file=sys.stderr)
            return 2
        try:
            ctxmgr = ContextManager(config)
            if args.command == COMMAND_LIST:
                ctxmgr.list_contexts()
            elif args.command == COMMAND_APPLY:
                ctxmgr.apply_context(args.__dict__[COMMAND_CTX_NAME]) # guaranteed to be present by argparse
        except Exception as e:
            print(f'error executing command:', e, file=sys.stderr)
            return 3
        return 0


def main():
    sys.exit(Runner().run())
        
if __name__ == '__main__':
    main()