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// Copyright (c) The Diem Core Contributors
// SPDX-License-Identifier: Apache-2.0

use crate::{
    storage::{BackupHandle, FileHandle},
    utils::error_notes::ErrorNotes,
};
use anyhow::Result;
use serde::Deserialize;
use std::path::Path;
use tokio::io::AsyncReadExt;

#[derive(Clone, Deserialize)]
pub struct EnvVar {
    pub key: String,
    pub value: String,
}

impl EnvVar {
    pub fn backup_name(value: String) -> Self {
        Self::new("BACKUP_NAME".to_string(), value)
    }

    pub fn file_name(value: String) -> Self {
        Self::new("FILE_NAME".to_string(), value)
    }

    pub fn file_handle(value: FileHandle) -> Self {
        Self::new("FILE_HANDLE".to_string(), value)
    }

    pub fn backup_handle(value: BackupHandle) -> Self {
        Self::new("BACKUP_HANDLE".to_string(), value)
    }

    pub fn new(key: String, value: String) -> Self {
        Self { key, value }
    }
}

#[derive(Clone, Default, Deserialize)]
pub struct Commands {
    /// Command line to create backup.
    /// input env vars:
    ///     $BACKUP_NAME
    /// expected output on stdout:
    ///     BackupHandle, trailing newline is trimmed
    pub create_backup: String,
    /// Command line to open a file for writing.
    /// input env vars:
    ///     $BACKUP_HANDLE returned from the previous command
    ///     $FILE_NAME
    /// stdin will be fed with byte stream.
    /// expected output on stdout:
    ///     FileHandle, trailing newline
    pub create_for_write: String,
    /// Command line to open a file for reading.
    /// input env vars:
    ///     $FILE_NAME
    /// expected stdout to stream out bytes of the file.
    pub open_for_read: String,
    /// Command line to save a line of metadata
    /// input env vars:
    ///     $FILE_NAME
    /// stdin will be fed with a line of text with a trailing newline.
    pub save_metadata_line: String,
    /// Command line to list all existing metadata file handles.
    /// expected stdout to stream out lines of file handles.
    pub list_metadata_files: String,
}

#[derive(Clone, Default, Deserialize)]
pub struct CommandAdapterConfig {
    /// Command lines that implements `BackupStorage` APIs.
    pub commands: Commands,
    /// Additional environment variables to be set when command lines are spawned.
    pub env_vars: Vec<EnvVar>,
}

impl CommandAdapterConfig {
    pub async fn load_from_file(path: &Path) -> Result<Self> {
        let path_str = path.to_str().unwrap_or_default();
        let mut file = tokio::fs::File::open(path).await.err_notes(path_str)?;
        let mut content = Vec::new();
        file.read_to_end(&mut content).await.err_notes(path_str)?;

        Ok(toml::from_slice(&content)?)
    }

    pub fn load_from_str(content: &str) -> Result<Self> {
        Ok(toml::from_str(content)?)
    }
}