//! Bitcoin domain names management using Nostr NIP-05 verification.
//! Allows users to register human-readable names linked to their DIDs
//! and verify names of peers via the NIP-05 protocol.

use anyhow::{Context, Result};
use serde::{Deserialize, Serialize};
use std::path::Path;
use tokio::fs;
use tracing::debug;

const NAMES_FILE: &str = "names.json";

/// A registered name linked to an identity.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct RegisteredName {
    pub id: String,
    pub name: String,
    pub domain: String,
    pub identity_id: String,
    pub did: String,
    pub nostr_pubkey: Option<String>,
    pub status: NameStatus,
    pub registered_at: String,
    pub expires_at: Option<String>,
    pub nip05: String,
}

#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
#[serde(rename_all = "lowercase")]
pub enum NameStatus {
    Active,
    Pending,
    Expired,
    Failed,
}

impl std::fmt::Display for NameStatus {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            NameStatus::Active => write!(f, "active"),
            NameStatus::Pending => write!(f, "pending"),
            NameStatus::Expired => write!(f, "expired"),
            NameStatus::Failed => write!(f, "failed"),
        }
    }
}

/// Stored names data.
#[derive(Debug, Clone, Serialize, Deserialize, Default)]
pub struct NamesStore {
    pub names: Vec<RegisteredName>,
}

/// NIP-05 verification result.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Nip05Resolution {
    pub name: String,
    pub domain: String,
    pub nostr_pubkey: Option<String>,
    pub relays: Vec<String>,
    pub verified: bool,
}

pub async fn load_names(data_dir: &Path) -> Result<NamesStore> {
    let path = data_dir.join(NAMES_FILE);
    if !path.exists() {
        return Ok(NamesStore::default());
    }
    let data = fs::read_to_string(&path)
        .await
        .context("Reading names store")?;
    serde_json::from_str(&data).context("Parsing names store")
}

pub async fn save_names(data_dir: &Path, store: &NamesStore) -> Result<()> {
    let path = data_dir.join(NAMES_FILE);
    let data = serde_json::to_string_pretty(store)?;
    fs::write(&path, data).await.context("Writing names store")
}

/// Register a new name linked to an identity.
pub async fn register_name(
    data_dir: &Path,
    name: &str,
    domain: &str,
    identity_id: &str,
    did: &str,
    nostr_pubkey: Option<&str>,
) -> Result<RegisteredName> {
    let mut store = load_names(data_dir).await?;

    let nip05 = format!("{}@{}", name, domain);

    // Check for duplicates
    if store.names.iter().any(|n| n.nip05 == nip05) {
        return Err(anyhow::anyhow!("Name {} is already registered", nip05));
    }

    let record = RegisteredName {
        id: uuid::Uuid::new_v4().to_string(),
        name: name.to_string(),
        domain: domain.to_string(),
        identity_id: identity_id.to_string(),
        did: did.to_string(),
        nostr_pubkey: nostr_pubkey.map(|s| s.to_string()),
        status: NameStatus::Active,
        registered_at: chrono::Utc::now().to_rfc3339(),
        expires_at: None,
        nip05,
    };

    debug!(name = %record.nip05, "Registered new name");
    store.names.push(record.clone());
    save_names(data_dir, &store).await?;
    Ok(record)
}

/// Remove a registered name.
pub async fn remove_name(data_dir: &Path, name_id: &str) -> Result<()> {
    let mut store = load_names(data_dir).await?;
    let original_len = store.names.len();
    store.names.retain(|n| n.id != name_id);
    if store.names.len() == original_len {
        return Err(anyhow::anyhow!("Name not found: {}", name_id));
    }
    save_names(data_dir, &store).await
}

/// Resolve a NIP-05 identifier (user@domain) to verify it.
pub async fn resolve_nip05(identifier: &str) -> Result<Nip05Resolution> {
    let parts: Vec<&str> = identifier.split('@').collect();
    if parts.len() != 2 {
        return Err(anyhow::anyhow!(
            "Invalid NIP-05 identifier: expected user@domain"
        ));
    }
    let name = parts[0];
    let domain = parts[1];

    let url = format!(
        "https://{}/.well-known/nostr.json?name={}",
        domain, name
    );

    let client = reqwest::Client::builder()
        .timeout(std::time::Duration::from_secs(10))
        .build()?;

    let response = client.get(&url).send().await;

    match response {
        Ok(resp) if resp.status().is_success() => {
            let body: serde_json::Value = resp.json().await?;
            let pubkey = body
                .get("names")
                .and_then(|names| names.get(name))
                .and_then(|v| v.as_str())
                .map(|s| s.to_string());

            let relays = if let Some(pk) = &pubkey {
                body.get("relays")
                    .and_then(|r| r.get(pk.as_str()))
                    .and_then(|v| v.as_array())
                    .map(|arr| {
                        arr.iter()
                            .filter_map(|v| v.as_str().map(|s| s.to_string()))
                            .collect()
                    })
                    .unwrap_or_default()
            } else {
                vec![]
            };

            Ok(Nip05Resolution {
                name: name.to_string(),
                domain: domain.to_string(),
                nostr_pubkey: pubkey.clone(),
                relays,
                verified: pubkey.is_some(),
            })
        }
        Ok(resp) => Err(anyhow::anyhow!(
            "NIP-05 verification failed: HTTP {}",
            resp.status()
        )),
        Err(_) => Ok(Nip05Resolution {
            name: name.to_string(),
            domain: domain.to_string(),
            nostr_pubkey: None,
            relays: vec![],
            verified: false,
        }),
    }
}

/// Link a registered name to a DID by updating its identity association.
pub async fn link_name_to_did(
    data_dir: &Path,
    name_id: &str,
    did: &str,
    identity_id: &str,
) -> Result<RegisteredName> {
    let mut store = load_names(data_dir).await?;
    let name = store
        .names
        .iter_mut()
        .find(|n| n.id == name_id)
        .ok_or_else(|| anyhow::anyhow!("Name not found: {}", name_id))?;

    name.did = did.to_string();
    name.identity_id = identity_id.to_string();
    let updated = name.clone();
    save_names(data_dir, &store).await?;
    Ok(updated)
}