use std::sync::Arc;

use axum::extract::State;
use axum::response::Redirect;
use axum_extra::extract::Form;
use serde::Deserialize;
use time::OffsetDateTime;
use time::format_description::well_known::Rfc3339;
use tracing::{info, warn};

use crate::analyze::{ANALYSIS_INPUT_FILE, AnalyzeJob, AnalyzeSender, DOCUMENT_FILE};
use crate::auth::AuthenticatedWebUser;
use crate::config::Config;
use crate::error::AppError;
use crate::events::{self, CaseEventKind, EventSender};
use crate::paths::{DeleteMarker, write_delete_marker};
use crate::routes::case_actions::{
    build_analysis_input, reset_case_artefacts, write_input_create_new,
};
use crate::routes::user_web::locate_case;

#[derive(Debug, Deserialize)]
pub struct BulkForm {
    action: String,
    /// Repeated `case_id=<uuid>` form fields. Empty for an empty selection
    /// (handled as a no-op).
    #[serde(default, rename = "case_id")]
    case_ids: Vec<String>,
}

/// POST /web/cases/bulk — apply `action` (analyze | delete) to every
/// selected case. Errors per case are logged but do not abort the batch:
/// a single bad/missing case must not block the rest.
pub async fn handle_bulk_action(
    user: AuthenticatedWebUser,
    State(config): State<Arc<Config>>,
    State(analyze_tx): State<AnalyzeSender>,
    State(events_tx): State<EventSender>,
    Form(form): Form<BulkForm>,
) -> Result<Redirect, AppError> {
    let user_root = config.data_path.join(&user.slug);

    match form.action.as_str() {
        "analyze" => {
            bulk_analyze(
                &config,
                &analyze_tx,
                &events_tx,
                &user.slug,
                &user_root,
                &form.case_ids,
            )
            .await
        }
        "delete" => bulk_delete(&events_tx, &user.slug, &user_root, &form.case_ids).await,
        "reset" => {
            if !user.is_admin() {
                warn!(slug = %user.slug, "bulk-reset: not admin");
                return Err(AppError::Forbidden("Nur für Admins".into()));
            }
            bulk_reset(&events_tx, &user.slug, &user_root, &form.case_ids).await
        }
        other => {
            warn!(slug = %user.slug, action = %other, "bulk: unknown action");
            return Err(AppError::BadRequest("Unbekannte Aktion".into()));
        }
    }

    Ok(Redirect::to("/web/cases"))
}

async fn bulk_analyze(
    config: &Config,
    analyze_tx: &AnalyzeSender,
    events_tx: &EventSender,
    slug: &str,
    user_root: &std::path::Path,
    case_ids: &[String],
) {
    if !config.llm_configured() {
        warn!(slug = %slug, "bulk-analyze: LLM not configured, skipping all");
        return;
    }
    let mut ok = 0usize;
    let mut skipped = 0usize;
    for case_id in case_ids {
        if uuid::Uuid::parse_str(case_id).is_err() {
            warn!(slug = %slug, case_id = %case_id, "bulk-analyze: invalid case_id");
            skipped += 1;
            continue;
        }
        let Some(case_dir) = locate_case(user_root, case_id).await else {
            warn!(slug = %slug, case_id = %case_id, "bulk-analyze: case not found");
            skipped += 1;
            continue;
        };
        // Same order as the single-case handler: drop old document first so
        // the UI doesn't keep showing "ausgewertet" during re-analysis.
        let document_path = case_dir.join(DOCUMENT_FILE);
        match tokio::fs::remove_file(&document_path).await {
            Ok(_) => {}
            Err(e) if e.kind() == std::io::ErrorKind::NotFound => {}
            Err(e) => {
                warn!(slug = %slug, case_id = %case_id, error = %e, "bulk-analyze: remove old document failed");
                skipped += 1;
                continue;
            }
        }
        let input = match build_analysis_input(&case_dir).await {
            Ok(i) => i,
            Err(_) => {
                warn!(slug = %slug, case_id = %case_id, "bulk-analyze: build_analysis_input failed");
                skipped += 1;
                continue;
            }
        };
        let input_path = case_dir.join(ANALYSIS_INPUT_FILE);
        if write_input_create_new(&input_path, &input).await.is_err() {
            warn!(slug = %slug, case_id = %case_id, "bulk-analyze: write input failed");
            skipped += 1;
            continue;
        }
        if analyze_tx
            .send(AnalyzeJob {
                case_dir: case_dir.clone(),
            })
            .is_err()
        {
            warn!(slug = %slug, case_id = %case_id, "bulk-analyze: send failed (worker gone)");
        }
        events::emit(events_tx, slug, case_id, CaseEventKind::AnalysisQueued);
        ok += 1;
    }
    info!(slug = %slug, ok, skipped, "bulk-analyze completed");
}

async fn bulk_delete(
    events_tx: &EventSender,
    slug: &str,
    user_root: &std::path::Path,
    case_ids: &[String],
) {
    // One batch UUID + one timestamp shared across the entire bulk action,
    // so undo can restore exactly this group.
    let batch = uuid::Uuid::new_v4();
    let deleted_at = match OffsetDateTime::now_utc().format(&Rfc3339) {
        Ok(s) => s,
        Err(e) => {
            warn!(slug = %slug, error = %e, "bulk-delete: failed to format timestamp");
            return;
        }
    };
    let mut ok = 0usize;
    let mut skipped = 0usize;
    for case_id in case_ids {
        if uuid::Uuid::parse_str(case_id).is_err() {
            warn!(slug = %slug, case_id = %case_id, "bulk-delete: invalid case_id");
            skipped += 1;
            continue;
        }
        let Some(case_dir) = locate_case(user_root, case_id).await else {
            warn!(slug = %slug, case_id = %case_id, "bulk-delete: case not found");
            skipped += 1;
            continue;
        };
        let marker = DeleteMarker {
            batch,
            deleted_at: deleted_at.clone(),
        };
        if let Err(e) = write_delete_marker(&case_dir, &marker).await {
            warn!(slug = %slug, case_id = %case_id, error = %e, "bulk-delete: write marker failed");
            skipped += 1;
            continue;
        }
        events::emit(events_tx, slug, case_id, CaseEventKind::CaseDeleted);
        ok += 1;
    }
    info!(slug = %slug, batch = %batch, ok, skipped, "bulk-delete completed");
}

async fn bulk_reset(
    events_tx: &EventSender,
    slug: &str,
    user_root: &std::path::Path,
    case_ids: &[String],
) {
    let mut ok = 0usize;
    let mut skipped = 0usize;
    for case_id in case_ids {
        if uuid::Uuid::parse_str(case_id).is_err() {
            warn!(slug = %slug, case_id = %case_id, "bulk-reset: invalid case_id");
            skipped += 1;
            continue;
        }
        let Some(case_dir) = locate_case(user_root, case_id).await else {
            warn!(slug = %slug, case_id = %case_id, "bulk-reset: case not found");
            skipped += 1;
            continue;
        };
        if let Err(e) = reset_case_artefacts(&case_dir).await {
            warn!(slug = %slug, case_id = %case_id, error = %e, "bulk-reset: failed");
            skipped += 1;
            continue;
        }
        events::emit(events_tx, slug, case_id, CaseEventKind::CaseReset);
        ok += 1;
    }
    info!(slug = %slug, ok, skipped, "bulk-reset completed");
}