use reqwest::Client;
use serde::Deserialize;
use sqlx::PgPool;
use tracing::{info, warn};

#[derive(Deserialize)]
struct ChannelConfig {
    #[serde(default = "default_warmup_mode")]
    warmup_mode: String,
    warmup_value: Option<i64>,
}

fn default_warmup_mode() -> String {
    "all".to_string()
}

struct ChannelInfo {
    id: String,
    name: String,
    config: ChannelConfig,
}

/// Oppvarming: les meldinger per kanal fra PG og last inn i SpacetimeDB.
/// Respekterer per-kanal warmup-konfigurasjon.
pub async fn run(
    pool: &PgPool,
    http: &Client,
    spacetimedb_url: &str,
    module: &str,
    default_limit: i64,
) -> anyhow::Result<()> {
    info!("Starter oppvarming (PG → SpacetimeDB)");

    // Hent kanaler med konfig
    let rows: Vec<(String, String, serde_json::Value)> = sqlx::query_as(
        "SELECT c.id::text, c.name, c.config FROM channels c JOIN nodes n ON n.id = c.id"
    )
    .fetch_all(pool)
    .await?;

    let channels: Vec<ChannelInfo> = rows.into_iter().map(|(id, name, config_val)| {
        let config: ChannelConfig = serde_json::from_value(config_val)
            .unwrap_or(ChannelConfig { warmup_mode: default_warmup_mode(), warmup_value: None });
        ChannelInfo { id, name, config }
    }).collect();

    if channels.is_empty() {
        info!("Ingen kanaler funnet — oppvarming fullført");
        return Ok(());
    }

    let active: Vec<&ChannelInfo> = channels.iter()
        .filter(|c| c.config.warmup_mode != "none")
        .collect();

    info!(
        total = channels.len(),
        active = active.len(),
        skipped = channels.len() - active.len(),
        "Kanaler funnet"
    );

    let mut total_messages = 0u64;
    let mut total_reactions = 0u64;

    for ch in &active {
        // Rydd kanalen i SpacetimeDB først
        if let Err(e) = call_reducer(http, spacetimedb_url, module, "clear_channel", &serde_json::json!({
            "channel_id": ch.id
        })).await {
            warn!(channel = %ch.name, error = %e, "Kunne ikke rydde kanal — hopper over");
            continue;
        }

        // Trådbasert henting: finn kvalifiserende tråder, hent alle meldinger i disse
        let rows = match ch.config.warmup_mode.as_str() {
            "all" => {
                // Alt — ingen filtrering
                fetch_messages_all(pool, &ch.id).await?
            },
            "messages" => {
                // Siste N tråder (sortert etter nyeste melding i tråden)
                let n = ch.config.warmup_value.unwrap_or(default_limit);
                fetch_messages_by_threads(pool, &ch.id, n).await?
            },
            "days" => {
                // Alle tråder med minst én melding i tidsvinduet
                let days = ch.config.warmup_value.unwrap_or(30);
                fetch_messages_by_days(pool, &ch.id, days).await?
            },
            _ => fetch_messages_all(pool, &ch.id).await?,
        };

        if rows.is_empty() {
            info!(channel = %ch.name, mode = %ch.config.warmup_mode, "Ingen meldinger å laste");
            continue;
        }

        // Bygg JSON-array
        let messages: Vec<serde_json::Value> = rows.iter().map(|r| {
            serde_json::json!({
                "id": r.0,
                "channel_id": r.1,
                "workspace_id": r.2,
                "author_id": r.3,
                "author_name": r.4,
                "body": r.5,
                "message_type": r.6,
                "reply_to": r.7.as_deref().unwrap_or(""),
                "created_at": r.8
            })
        }).collect();

        let count = messages.len();
        let json_str = serde_json::to_string(&messages)?;

        if let Err(e) = call_reducer(http, spacetimedb_url, module, "load_messages", &serde_json::json!({
            "messages_json": json_str
        })).await {
            warn!(channel = %ch.name, error = %e, "Feil ved lasting av meldinger");
            continue;
        }

        total_messages += count as u64;

        // Hent reaksjoner for denne kanalens meldinger
        let reaction_rows: Vec<(String, String, String, String)> = sqlx::query_as(
            r#"
            SELECT
                mr.message_id::text,
                COALESCE(mr.user_id, ''),
                COALESCE(u.name, 'Ukjent'),
                mr.reaction
            FROM message_reactions mr
            JOIN messages m ON m.id = mr.message_id
            LEFT JOIN users u ON u.authentik_id = mr.user_id
            WHERE m.channel_id = $1::uuid
            "#
        )
        .bind(&ch.id)
        .fetch_all(pool)
        .await?;

        if !reaction_rows.is_empty() {
            let reactions: Vec<serde_json::Value> = reaction_rows.iter().map(|r| {
                serde_json::json!({
                    "message_id": r.0,
                    "user_id": r.1,
                    "user_name": r.2,
                    "reaction": r.3
                })
            }).collect();

            let reactions_json = serde_json::to_string(&reactions)?;
            if let Err(e) = call_reducer(http, spacetimedb_url, module, "load_reactions", &serde_json::json!({
                "reactions_json": reactions_json
            })).await {
                warn!(channel = %ch.name, error = %e, "Feil ved lasting av reaksjoner");
            } else {
                total_reactions += reaction_rows.len() as u64;
            }
        }

        info!(
            channel = %ch.name,
            mode = %ch.config.warmup_mode,
            value = ?ch.config.warmup_value,
            messages = count,
            reactions = reaction_rows.len(),
            "Kanal oppvarmet"
        );
    }

    info!(
        channels = active.len(),
        messages = total_messages,
        reactions = total_reactions,
        "Oppvarming fullført"
    );

    Ok(())
}

type MessageRow = (String, String, String, String, String, String, String, Option<String>, String);

const MESSAGE_COLUMNS: &str = r#"
    m.id::text,
    m.channel_id::text,
    n.workspace_id::text,
    COALESCE(m.author_id, ''),
    COALESCE(u.name, 'Ukjent'),
    COALESCE(m.body, ''),
    COALESCE(m.message_type, 'text'),
    m.reply_to::text,
    m.created_at::text
"#;

const MESSAGE_JOINS: &str = r#"
    JOIN nodes n ON n.id = m.id
    LEFT JOIN users u ON u.authentik_id = m.author_id
"#;

/// Hent alle meldinger i en kanal.
async fn fetch_messages_all(pool: &PgPool, channel_id: &str) -> anyhow::Result<Vec<MessageRow>> {
    let query = format!(
        "SELECT {} FROM messages m {} WHERE m.channel_id = $1::uuid ORDER BY m.created_at",
        MESSAGE_COLUMNS, MESSAGE_JOINS
    );
    Ok(sqlx::query_as(&query).bind(channel_id).fetch_all(pool).await?)
}

/// Hent de N nyeste trådene + alle meldinger i disse.
/// En "tråd" = en rotmelding (reply_to IS NULL) med alle svar.
/// Sortert etter nyeste melding i tråden.
async fn fetch_messages_by_threads(pool: &PgPool, channel_id: &str, limit: i64) -> anyhow::Result<Vec<MessageRow>> {
    // Finn rot-IDer for de N nyeste trådene.
    // En tråds "siste aktivitet" er max(created_at) blant rot + alle svar.
    // Løse meldinger (reply_to peker på noe utenfor kanalen) teller som egen tråd.
    let query = format!(
        r#"
        WITH thread_roots AS (
            -- Finn rot for hver melding: følg reply_to opp til NULL, eller til utenfor kanalen
            SELECT DISTINCT COALESCE(
                (SELECT r.id FROM messages r
                 WHERE r.id = m.reply_to AND r.channel_id = m.channel_id AND r.reply_to IS NULL),
                CASE WHEN m.reply_to IS NULL THEN m.id END,
                m.id  -- orphan-svar → behandles som egen tråd
            ) AS root_id
            FROM messages m
            WHERE m.channel_id = $1::uuid
        ),
        ranked_threads AS (
            SELECT tr.root_id,
                   max(m.created_at) AS last_activity
            FROM thread_roots tr
            JOIN messages m ON m.channel_id = $1::uuid
                AND (m.id = tr.root_id OR m.reply_to = tr.root_id)
            GROUP BY tr.root_id
            ORDER BY last_activity DESC
            LIMIT $2
        )
        SELECT {}
        FROM messages m
        {}
        WHERE m.channel_id = $1::uuid
          AND (m.id IN (SELECT root_id FROM ranked_threads)
               OR m.reply_to IN (SELECT root_id FROM ranked_threads))
        ORDER BY m.created_at
        "#,
        MESSAGE_COLUMNS, MESSAGE_JOINS
    );
    Ok(sqlx::query_as(&query).bind(channel_id).bind(limit).fetch_all(pool).await?)
}

/// Hent alle tråder som har minst én melding innen siste N dager.
/// Inkluderer hele tråden (også eldre trådstartere).
async fn fetch_messages_by_days(pool: &PgPool, channel_id: &str, days: i64) -> anyhow::Result<Vec<MessageRow>> {
    let query = format!(
        r#"
        WITH qualifying_roots AS (
            -- Finn trådrøtter for meldinger innenfor tidsvinduet
            SELECT DISTINCT COALESCE(
                (SELECT r.id FROM messages r
                 WHERE r.id = m.reply_to AND r.channel_id = m.channel_id AND r.reply_to IS NULL),
                CASE WHEN m.reply_to IS NULL THEN m.id END,
                m.id
            ) AS root_id
            FROM messages m
            WHERE m.channel_id = $1::uuid
              AND m.created_at >= now() - make_interval(days => $2)
        )
        SELECT {}
        FROM messages m
        {}
        WHERE m.channel_id = $1::uuid
          AND (m.id IN (SELECT root_id FROM qualifying_roots)
               OR m.reply_to IN (SELECT root_id FROM qualifying_roots))
        ORDER BY m.created_at
        "#,
        MESSAGE_COLUMNS, MESSAGE_JOINS
    );
    Ok(sqlx::query_as(&query).bind(channel_id).bind(days as i32).fetch_all(pool).await?)
}

async fn call_reducer(
    http: &Client,
    base_url: &str,
    module: &str,
    reducer: &str,
    args: &serde_json::Value,
) -> anyhow::Result<()> {
    let url = format!("{}/v1/database/{}/call/{}", base_url, module, reducer);
    let resp = http
        .post(&url)
        .json(args)
        .send()
        .await?;

    if !resp.status().is_success() {
        let status = resp.status();
        let body = resp.text().await.unwrap_or_default();
        anyhow::bail!("{} feilet ({}): {}", reducer, status, body);
    }

    Ok(())
}