//! Integration with `clap`
//!
//! CLI argument structs are defined in this module. Execution logic for each
//! command goes in a submodule.

use std::{path::PathBuf, str::FromStr};

use clap::{Parser, Subcommand};

use crate::error;

mod migrate_db;
mod serve;

/// Command line arguments
#[derive(Parser)]
#[clap(
    about,
    version = crate::version(),
)]
pub(crate) struct Args {
    #[clap(subcommand)]
    pub(crate) command: Command,
}

#[derive(Subcommand)]
pub(crate) enum Command {
    /// Run the server.
    Serve(ServeArgs),

    /// Commands for interacting with the database.
    #[clap(subcommand)]
    Db(DbCommand),
}

/// Wrapper for the `--config` arg.
///
/// This exists to centralize the `mut_arg` code that sets the help value based
/// on runtime information.
#[derive(clap::Args)]
#[clap(mut_arg("config", |x| {
    let help = "Set the path to the configuration file";
    x.help(help).long_help(format!(
        "{}\n\nIf this option is specified, the provided value is used \
         as-is.\n\nIf this option is not specified, then the XDG Base \
         Directory Specification is followed, searching for the path `{}` \
         in the configuration directories.
        ",
        help,
        crate::config::DEFAULT_PATH.display(),
    ))
}))]
pub(crate) struct ConfigArg {
    /// Path to the configuration file
    #[clap(long, short)]
    pub(crate) config: Option<PathBuf>,
}

#[derive(clap::Args)]
pub(crate) struct ServeArgs {
    #[clap(flatten)]
    pub(crate) config: ConfigArg,
}

#[derive(Subcommand)]
pub(crate) enum DbCommand {
    /// Migrate database from one server implementation to another.
    ///
    /// This command is not protected against symlink-swapping attacks. Do not
    /// use it when any subdirectories or parents of the `--in`, `--out`, or
    /// `--inplace` directories may be written by an untrusted user during
    /// execution.
    Migrate(MigrateDbArgs),
}

#[derive(clap::Args)]
pub(crate) struct MigrateDbArgs {
    #[clap(flatten)]
    config: ConfigArg,

    /// Target server implementation to migrate database to.
    ///
    /// If migrating to the current version of grapevine, specify the version
    /// as 'grapevine'.
    ///
    /// If migrating to a released version of conduit, specified the version
    /// of conduit as `conduit-{version}` (example: `conduit-0.8.0`). If
    /// migrating to an unreleased conduit build, instead specify the raw
    /// database version as `conduit-db-{version}` (example: `conduit-db-13`).
    /// The raw database version can be found by looking at the
    /// `latest_database_version` variable in `src/database/mod.rs`.
    ///
    /// The server implementation used for the current database will be
    /// detected automatically, and does not need to be specified.
    #[clap(long)]
    pub(crate) to: DbMigrationTarget,

    /// Path to read database from.
    #[clap(long = "in", short)]
    pub(crate) in_path: PathBuf,

    /// Path to write migrated database to.
    #[clap(long = "out", short)]
    pub(crate) out_path: PathBuf,
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub(crate) enum DbMigrationTarget {
    /// The latest grapevine db version
    ///
    /// Example:
    ///
    /// ```
    /// assert_eq!("grapevine".parse(), Ok(DbMigrationTarget::Grapevine))
    /// ```
    Grapevine,
    /// A conduit-compatible db version.
    ///
    /// This may either be specified as a released version number or directly
    /// as a database version. The raw database version must be used when
    /// migrating to a conduit deployment built from an unreleased commit
    /// on the `next` branch.
    Conduit(ConduitDbVersion),
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub(crate) enum ConduitDbVersion {
    /// A conduit release version number
    ///
    /// Example:
    ///
    /// ```
    /// assert_eq!(
    ///     "conduit-0.8.0".parse(),
    ///     Ok(DbMigrationTarget::Conduit(ConduitDbVersion::Release("0.8.0")))
    /// );
    /// ```
    Release(String),
    /// A raw database version
    ///
    /// This corresponds directly to a
    /// [`crate::service::globals::DbVersion::Conduit`] version.
    ///
    /// Example:
    ///
    /// ```
    /// assert_eq!(
    ///     "conduit-db-13".parse(),
    ///     Ok(DbMigrationTarget::Conduit(ConduitDbVersion::Db(13)))
    /// );
    /// ```
    Db(u64),
}

#[derive(thiserror::Error, Debug)]
#[error("invalid db migration target version")]
pub(crate) struct DbMigrationTargetParseError;

impl FromStr for DbMigrationTarget {
    type Err = DbMigrationTargetParseError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if s == "grapevine" {
            Ok(DbMigrationTarget::Grapevine)
        } else if let Some(version) = s.strip_prefix("conduit-db-") {
            let version =
                version.parse().map_err(|_| DbMigrationTargetParseError)?;
            Ok(DbMigrationTarget::Conduit(ConduitDbVersion::Db(version)))
        } else if let Some(version) = s.strip_prefix("conduit-") {
            Ok(DbMigrationTarget::Conduit(ConduitDbVersion::Release(
                version.to_owned(),
            )))
        } else {
            Err(DbMigrationTargetParseError)
        }
    }
}

impl Args {
    pub(crate) async fn run(self) -> Result<(), error::Main> {
        match self.command {
            Command::Serve(args) => serve::run(args).await?,
            Command::Db(DbCommand::Migrate(args)) => {
                migrate_db::run(args).await?;
            }
        }
        Ok(())
    }
}