use serde::Serialize;
use serde_json::Value;
use std::io::Write;
use std::process::{Command, Stdio};

const NODE_ALIAS: &str = "xx-gz-001";
const CHANNEL_ROOT: &str = "/var/lib/guanghu/education-data/channels/GH-EDU-CHANNEL-XX-001";

#[derive(Serialize)]
#[serde(rename_all = "camelCase")]
struct ChannelSnapshot {
    node: Value,
    fifth_domain_link: Value,
    module_registry: Value,
    update_authority: Value,
    channel: Value,
    code_channel: Value,
}

fn ssh_output(remote_command: &str) -> Result<String, String> {
    let output = Command::new("/usr/bin/ssh")
        .args([
            "-o",
            "BatchMode=yes",
            "-o",
            "ConnectTimeout=10",
            NODE_ALIAS,
            remote_command,
        ])
        .output()
        .map_err(|error| format!("SSH_LAUNCH_FAILED:{error}"))?;

    if !output.status.success() {
        return Err(format!(
            "SSH_REMOTE_FAILED:{}",
            String::from_utf8_lossy(&output.stderr).trim()
        ));
    }

    String::from_utf8(output.stdout).map_err(|error| format!("SSH_OUTPUT_INVALID_UTF8:{error}"))
}

fn read_remote_json(path: &str) -> Result<Value, String> {
    let payload = ssh_output(&format!("cat {path}"))?;
    serde_json::from_str(&payload).map_err(|error| format!("REMOTE_JSON_INVALID:{path}:{error}"))
}

#[tauri::command]
fn connect_channel() -> Result<ChannelSnapshot, String> {
    let code_version = ssh_output("curl -fsS http://127.0.0.1:3901/api/v1/version")?;
    let repository_search =
        ssh_output("curl -fsS 'http://127.0.0.1:3901/api/v1/repos/search?limit=20'")?;

    Ok(ChannelSnapshot {
        node: read_remote_json("/var/lib/guanghu/protocol/node.json")?,
        fifth_domain_link: read_remote_json(
            "/var/lib/guanghu/receipts/XX-GZ-001/FIFTH-DOMAIN-LINK-CURRENT.json",
        )?,
        module_registry: read_remote_json("/opt/guanghu/protocol/current/module-registry.json")?,
        update_authority: read_remote_json("/opt/guanghu/protocol/current/update-authority.json")?,
        channel: read_remote_json("/opt/guanghu/protocol/current/xiaoxin-channel.json")?,
        code_channel: serde_json::json!({
            "version": serde_json::from_str::<Value>(&code_version)
                .map_err(|error| format!("CODE_CHANNEL_VERSION_INVALID:{error}"))?,
            "repositories": serde_json::from_str::<Value>(&repository_search)
                .map_err(|error| format!("CODE_CHANNEL_REPOSITORIES_INVALID:{error}"))?
        }),
    })
}

fn channel_file(kind: &str) -> Result<(&'static str, &'static str), String> {
    match kind {
        "document" => Ok(("teacher-training-plan.md", "GH-EDU-OFFICE-DOC-001")),
        "sheet" => Ok(("teacher-training-data.csv", "GH-EDU-OFFICE-SHEET-001")),
        _ => Err(format!("UNREGISTERED_CHANNEL_FILE:{kind}")),
    }
}

#[tauri::command]
fn read_channel_file(kind: String) -> Result<String, String> {
    let (filename, _) = channel_file(&kind)?;
    ssh_output(&format!(
        "path='{CHANNEL_ROOT}/documents/{filename}'; if [ -f \"$path\" ]; then cat \"$path\"; fi"
    ))
}

#[tauri::command]
fn save_channel_file(kind: String, content: String) -> Result<Value, String> {
    let (filename, module_id) = channel_file(&kind)?;
    let path = format!("{CHANNEL_ROOT}/documents/{filename}");
    let receipt = format!("{CHANNEL_ROOT}/receipts/{kind}-CURRENT.json");
    let remote_command = format!(
        "set -eu; \
         install -d -m 700 '{CHANNEL_ROOT}/documents' '{CHANNEL_ROOT}/receipts'; \
         path='{path}'; tmp=\"${{path}}.tmp.$$\"; umask 077; cat > \"$tmp\"; mv \"$tmp\" \"$path\"; \
         sha=$(sha256sum \"$path\" | awk '{{print $1}}'); \
         now=$(date -u +%Y-%m-%dT%H:%M:%SZ); \
         receipt='{receipt}'; rtmp=\"${{receipt}}.tmp.$$\"; \
         printf '{{\"schema\":\"guanghu.channel-write-receipt/v1\",\"channelId\":\"GH-EDU-CHANNEL-XX-001\",\"nodeId\":\"XX-GZ-001\",\"moduleId\":\"{module_id}\",\"kind\":\"{kind}\",\"sha256\":\"%s\",\"writtenAt\":\"%s\",\"state\":\"PASS_100\"}}\\n' \"$sha\" \"$now\" > \"$rtmp\"; \
         mv \"$rtmp\" \"$receipt\"; cat \"$receipt\""
    );

    let mut child = Command::new("/usr/bin/ssh")
        .args([
            "-o",
            "BatchMode=yes",
            "-o",
            "ConnectTimeout=10",
            NODE_ALIAS,
            &remote_command,
        ])
        .stdin(Stdio::piped())
        .stdout(Stdio::piped())
        .stderr(Stdio::piped())
        .spawn()
        .map_err(|error| format!("SSH_SAVE_LAUNCH_FAILED:{error}"))?;

    child
        .stdin
        .take()
        .ok_or_else(|| "SSH_SAVE_STDIN_UNAVAILABLE".to_string())?
        .write_all(content.as_bytes())
        .map_err(|error| format!("SSH_SAVE_WRITE_FAILED:{error}"))?;

    let output = child
        .wait_with_output()
        .map_err(|error| format!("SSH_SAVE_WAIT_FAILED:{error}"))?;
    if !output.status.success() {
        return Err(format!(
            "SSH_SAVE_REMOTE_FAILED:{}",
            String::from_utf8_lossy(&output.stderr).trim()
        ));
    }

    serde_json::from_slice(&output.stdout)
        .map_err(|error| format!("SSH_SAVE_RECEIPT_INVALID:{error}"))
}

#[cfg_attr(mobile, tauri::mobile_entry_point)]
pub fn run() {
    tauri::Builder::default()
        .invoke_handler(tauri::generate_handler![
            connect_channel,
            read_channel_file,
            save_channel_file
        ])
        .run(tauri::generate_context!())
        .expect("failed to run Guanghu Education Subdomain OS");
}