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

COMMAND_LIST = 'list'
COMMAND_LOAD = 'load'
COMMAND_SAVE = 'save'
COMMAND_CTX_NAME = 'context_name'
COMMANDS_ALL = [COMMAND_LIST, COMMAND_LOAD, COMMAND_SAVE]

SECTION_GENERAL = 'general'
KEY_CONTEXTS_PATH = 'contexts_path'
KEY_TASKS = 'tasks'
KEY_DRY_RUN = 'dry_run'
KEY_MANAGED_DIR = 'managed_directory'

SECTION_TASK = 'task'
KEY_SRC_PATH = 'source_path'
KEY_DST_PATH = 'target_path'
KEY_RELOAD = 'reload'
KEY_ACTIONS = 'actions'
KEY_SYMLINK = 'symlinks'
KEY_COMMAND = 'commands'
KEY_SCRIPT = 'scripts'
KEY_CODE = 'code'
ACTIONS_ALL = [KEY_SYMLINK, KEY_COMMAND, KEY_SCRIPT, KEY_CODE]

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])
        

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.actions = conf.get(KEY_ACTIONS) or [KEY_SYMLINK] # default is to just symlink all
        self.symlinks = conf.get(KEY_SYMLINK)
        self.commands = conf.get(KEY_COMMAND)
        self.scripts = conf.get(KEY_SCRIPT)
        self.code = conf.get(KEY_CODE)
        self.reload_command = conf.get(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:
        for a in self.actions:
            if a == KEY_SYMLINK:
                self._symlink()
            elif a == KEY_COMMAND:
                self._run_commands()
            elif a == KEY_SCRIPT:
                self._run_scripts()
            elif a == KEY_CODE:
                self._run_code()
        if self.reload_command and not self.dry_run:
            self.shell.exec_command(self.reload_command)

    def _symlink(self) -> None:
        if not self.symlinks: # will symlink everything we have then
            self.symlinks = [{entry.name: entry.name} for entry in os.scandir(self.src)]
        for l in self.symlinks:
            for k, v in l.items():
                src, dst = os.path.join(self.src, k), os.path.join(self.dst, v)
                if self.dry_run:
                    print("will remove:", dst, "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 = [entry.name for entry in os.scandir(self.src) if entry.is_file()]
        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) -> None:
        if self.dry_run:
            print("will execute code:", self.code)
            return
        self.shell.exec_snippet(self.code)

    def _run_commands(self) -> None:
        if self.dry_run:
            print("will execute:", self.commands)
            return
        for cmd in self.commands:
            self.shell.exec_command(cmd)


class ContextManagerConfig(object):
    def __init__(self, conf_file_path: str):
        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:
            raise ValueError(f'section "{SECTION_GENERAL}" not found in the config')

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

        if SECTION_TASK not in self.config: # valid case with all defaults
            self.config[SECTION_TASK] = dict()

        errors, err_count = list(), 0 # fuck it again
        self.dry_run = self.config[SECTION_GENERAL].get(KEY_DRY_RUN) or False
        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_CONTEXTS_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_CONTEXTS_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_MANAGED_DIR) 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_MANAGED_DIR}" of section "{SECTION_GENERAL}" must be absolute or relative to home: "~/{self.managed_path}"')

        tasks = self.config.get(SECTION_TASK)
        for name, t in tasks.items():
            errstr = f'for task "{name}"' 
            for k in list(t.keys()): # we might change t
                v = t[k]
                if k in [KEY_SRC_PATH, KEY_DST_PATH, KEY_CODE] and not isinstance(v, str):
                    err_count +=1
                    errors.append(f'{err_count}. {errstr} key "{k}" must be a string') 
                    continue
                elif k in [KEY_COMMAND, KEY_SCRIPT, KEY_RELOAD, KEY_ACTIONS, KEY_SYMLINK] and not isinstance(v, list):
                    err_count +=1
                    errors.append(f'{err_count}. {errstr} key "{k}" must be an array')
                    continue
                if k == KEY_COMMAND and not all(is_arr_of_str(elem) for elem in v):
                    err_count +=1
                    errors.append(f'{err_count}. {errstr} all elements of "{KEY_COMMAND}" must be arrays of strings')
                if k == KEY_SCRIPT and not is_arr_of_str(v):
                    err_count +=1
                    errors.append(f'{err_count}. {errstr} "{KEY_SCRIPT}" must be array of strings')
                if k == KEY_SYMLINK and not all(is_dict_of_str(elem) for elem in v):
                    err_count +=1
                    errors.append(f'{err_count}. {errstr} all elements of "{KEY_SYMLINK}" array must be mappings (inline tables) of strings')
                if k == KEY_ACTIONS and not is_arr_of_str(v):
                    err_count +=1
                    errors.append(f'{err_count}. {errstr} "{KEY_ACTIONS}" must be array if strings')
                if k == KEY_ACTIONS and not all(a in ACTIONS_ALL for a in v):
                    err_count +=1
                    errors.append(f'{err_count}. {errstr} found invalid actions: {[a for a in v if a not in ACTIONS_ALL]} in key "{KEY_ACTIONS}", valid actions are: {ACTIONS_ALL}')
                if k == KEY_RELOAD and not is_arr_of_str(v):
                    err_count +=1
                    errors.append(f'{err_count}. {errstr} "{KEY_RELOAD}" must be array of strings')
                if 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}):')
            print('\n'.join(errors))
            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:
            task_path = os.path.join(ctx_path, name) 
            target_path = os.path.join(self.managed_path, name)
            t = Task(name, task_path, target_path, self.config[SECTION_TASK].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 print_contexts_list(self) -> str:
        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'))
        subp = p.add_subparsers(help='command to execute', dest='command')
        loadp = subp.add_parser(COMMAND_LOAD, help='load context (provide name of context)')
        loadp.add_argument(COMMAND_CTX_NAME, help='name of context to load')
        listp = subp.add_parser(COMMAND_LIST, help='list available contexts')
        savep = subp.add_parser(COMMAND_SAVE, help='save current context (provide name of context)')
        savep.add_argument(COMMAND_CTX_NAME, help='name of context to save')
        try: # just in case
            args = p.parse_args()
        except Exception as e:
            print("error parsing command-line arguments:", e)
            return 1
        try:
            config = ContextManagerConfig(args.config)
        except Exception as e:
            print("error loading config:", e)
            return 2
        try:
            ctxmgr = ContextManager(config)
            if args.command == COMMAND_LIST:
                ctxmgr.print_contexts_list()
            elif args.command == COMMAND_LOAD:
                ctxmgr.apply_context(args.__dict__[COMMAND_CTX_NAME]) # guaranteed to be present by argparse
            elif args.command == COMMAND_SAVE:
                raise Exception('"save" not implemented')
        except Exception as e:
            print(f'error executing command:', e)
            return 3
        return 0


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