use anyhow::bail;
use nostr::JsonUtil;
use nostr::Event;
use std::time::{SystemTime, UNIX_EPOCH};

use crate::db::{FileRecord, TorrentRecord};
use crate::enrich::parser as title_parser;
use crate::torznab::categories::tcat_to_newznab;

static INFO_HASH_RE: std::sync::OnceLock<regex::Regex> = std::sync::OnceLock::new();

fn info_hash_re() -> &'static regex::Regex {
    INFO_HASH_RE.get_or_init(|| regex::Regex::new(r"^[0-9a-fA-F]{40}$").unwrap())
}

/// Parse a kind 2003 Nostr event into a TorrentRecord ready for storage.
pub fn parse(event: &Event) -> anyhow::Result<TorrentRecord> {
    // nostr-sdk validates signatures before we receive events; no need to re-validate here.
    if event.kind.as_u16() != 2003 {
        bail!("wrong kind: {}", event.kind.as_u16());
    }

    let now = SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .unwrap_or_default()
        .as_secs() as i64;

    let mut rec = TorrentRecord {
        event_id: event.id.to_hex(),
        info_hash: String::new(),
        pubkey: event.pubkey.to_hex(),
        created_at: event.created_at.as_secs() as i64,
        ingested_at: now,
        title: String::new(),
        description: String::new(),
        size_bytes: None,
        category: String::new(),
        newznab_cat: None,
        imdb_id: String::new(),
        tmdb_id: String::new(),
        tvdb_id: String::new(),
        season: None,
        episode: None,
        quality: String::new(),
        source: String::new(),
        raw_event: event.as_json(),
        trackers: vec![],
        tags: vec![],
        files: vec![],
    };

    let mut total_size: i64 = 0;
    let mut has_size = false;
    let mut tcat_cat: Option<i32> = None;
    let mut newznab_cat: Option<i32> = None;
    let mut tcat_str = String::new();

    for tag in event.tags.iter() {
        let tag_vec = tag.as_slice();
        if tag_vec.len() < 2 {
            continue;
        }
        match tag_vec[0].as_str() {
            "x" => {
                let hash = tag_vec[1].to_lowercase();
                if !info_hash_re().is_match(&hash) {
                    bail!("invalid info_hash: {:?}", tag_vec[1]);
                }
                rec.info_hash = hash;
            }
            "title" => {
                rec.title = tag_vec[1].clone();
            }
            "file" => {
                let path = tag_vec[1].clone();
                let sz = tag_vec.get(2).and_then(|s| s.parse::<i64>().ok());
                if let Some(s) = sz {
                    total_size += s;
                    has_size = true;
                }
                rec.files.push(FileRecord { path, size_bytes: sz });
            }
            "tracker" => {
                rec.trackers.push(tag_vec[1].clone());
            }
            "i" => {
                parse_i_tag(&tag_vec[1], &mut rec, &mut tcat_cat, &mut newznab_cat, &mut tcat_str);
            }
            "t" => {
                rec.tags.push(tag_vec[1].clone());
            }
            _ => {}
        }
    }

    if rec.info_hash.is_empty() {
        bail!("missing x (info_hash) tag");
    }

    // newznab: overrides tcat:
    rec.newznab_cat = newznab_cat.or(tcat_cat);
    if !tcat_str.is_empty() {
        rec.category = tcat_str;
    }

    // Title fallback: first line of content.
    if rec.title.is_empty() {
        rec.title = event.content
            .split('\n')
            .next()
            .unwrap_or("")
            .trim()
            .to_owned();
    }
    if rec.title.is_empty() {
        bail!("event has no title");
    }

    // Apply title parser to fill in fields not supplied by tags.
    let parsed = title_parser::parse(&rec.title);
    if rec.season.is_none() && parsed.season.is_some() {
        rec.season = parsed.season;
    }
    if rec.episode.is_none() && parsed.episode.is_some() {
        rec.episode = parsed.episode;
    }
    if rec.quality.is_empty() {
        if let Some(q) = parsed.quality {
            rec.quality = q;
        }
    }
    if rec.source.is_empty() {
        if let Some(s) = parsed.source {
            rec.source = s;
        }
    }

    rec.description = event.content.clone();
    if has_size {
        rec.size_bytes = Some(total_size);
    }

    Ok(rec)
}

fn parse_i_tag(
    value: &str,
    rec: &mut TorrentRecord,
    tcat_cat: &mut Option<i32>,
    newznab_cat: &mut Option<i32>,
    tcat_str: &mut String,
) {
    if let Some(rest) = value.strip_prefix("newznab:") {
        if let Ok(cat) = rest.parse::<i32>() {
            *newznab_cat = Some(cat);
        }
    } else if let Some(rest) = value.strip_prefix("tcat:") {
        *tcat_str = rest.to_owned();
        if tcat_cat.is_none() {
            *tcat_cat = Some(tcat_to_newznab(rest));
        }
    } else if let Some(rest) = value.strip_prefix("imdb:") {
        rec.imdb_id = rest.to_owned();
    } else if let Some(rest) = value.strip_prefix("tmdb:movie:") {
        rec.tmdb_id = format!("movie:{rest}");
    } else if let Some(rest) = value.strip_prefix("tmdb:tv:") {
        rec.tmdb_id = format!("tv:{rest}");
    } else if let Some(rest) = value.strip_prefix("tvdb:") {
        rec.tvdb_id = rest.to_owned();
    }
}