use std::path::Path;
use std::sync::Arc;
use std::sync::atomic::Ordering;

use askama::Template;
use axum::extract::State;
use axum::response::Html;
use tracing::{info, warn};

use time::{Date, OffsetDateTime, format_description::well_known::Rfc3339};

use crate::PipelineState;
use crate::analyze::{
    ANALYSIS_INPUT_FILE, DOCUMENT_FILE, auto_trigger, recovery as analyze_recovery,
};
use crate::auth::AuthenticatedWebUser;
use crate::case_id::{CaseId, CaseIdPath};
use crate::config::Config;
use crate::error::AppError;
use crate::events::EventSender;
use crate::routes::case_actions::read_document;
use crate::routes::web::{RecordingView, scan_recordings};
use crate::transcribe::recovery as transcribe_recovery;

struct UserCaseView {
    case_id: String,
    most_recent: String,
    /// HH:MM of the most recent recording in UTC — no-JS fallback.
    /// Browser script replaces the displayed text with the browser-local
    /// equivalent via the parallel `recorded_at_iso` field.
    time_hms_utc: String,
    /// Full RFC3339 UTC timestamp of the most recent recording. Fed into
    /// the HTML `<time datetime="...">` attribute so browser JS can
    /// render it in the doctor's actual timezone (which may differ from
    /// the server's, e.g. server on Bahamas, doctor in Germany).
    recorded_at_iso: String,
    oneliner: Option<String>,
    recordings_count: usize,
    analyzing: bool,
    has_document: bool,
    /// True iff the inline "Analysieren"-button should be enabled.
    /// Requires: not currently analyzing, all non-failed recordings
    /// transcribed, and an LLM is configured.
    can_analyze: bool,
}

/// Parse a recording filename `YYYY-MM-DDTHH-MM-SSZ.m4a[.failed]` as UTC
/// and return `(Date, Rfc3339String)`. None on malformed input.
fn utc_date_and_iso_of(filename: &str) -> Option<(Date, String)> {
    let s = filename.get(..20)?;
    if s.as_bytes().get(19) != Some(&b'Z') {
        return None;
    }
    // Filename uses `-` between H/M/S; Rfc3339 wants `:`. Patch two bytes.
    let mut buf = [0u8; 20];
    buf.copy_from_slice(s.as_bytes());
    buf[13] = b':';
    buf[16] = b':';
    let fixed = std::str::from_utf8(&buf).ok()?;
    let dt = OffsetDateTime::parse(fixed, &Rfc3339).ok()?;
    Some((dt.date(), fixed.to_owned()))
}

/// Group cases (already sorted newest-first) into UTC-date buckets. The
/// label is the raw ISO date string (e.g. `2026-04-18`); browser JS
/// re-labels the current/previous UTC date to "Heute"/"Gestern". Note:
/// grouping is by UTC day, which may drift from the doctor's local-day
/// perception around midnight — acceptable tradeoff; full Browser-TZ
/// grouping would require a larger client-side restructure.
fn group_by_utc_date(cases: Vec<UserCaseView>) -> Vec<DateGroup> {
    let today = OffsetDateTime::now_utc().date();
    let mut groups: Vec<DateGroup> = Vec::new();
    for case in cases {
        let d = utc_date_and_iso_of(&case.most_recent)
            .map(|(d, _)| d)
            .unwrap_or(today);
        let label = d.to_string();
        match groups.last_mut() {
            Some(g) if g.label == label => g.cases.push(case),
            _ => groups.push(DateGroup {
                label,
                cases: vec![case],
            }),
        }
    }
    groups
}

/// Extract `HH:MM` from a recording filename of the form
/// `YYYY-MM-DDTHH-MM-SSZ.m4a[.failed]`. Returns `""` on any mismatch.
/// Used only as a no-JS fallback — the canonical value rendered in the
/// browser comes from the `<time datetime>`-based script.
fn extract_hhmm_utc(filename: &str) -> String {
    let (Some(h), Some(m)) = (filename.get(11..13), filename.get(14..16)) else {
        return String::new();
    };
    if h.bytes().all(|b| b.is_ascii_digit()) && m.bytes().all(|b| b.is_ascii_digit()) {
        format!("{h}:{m}")
    } else {
        String::new()
    }
}

/// Build an RFC3339 UTC timestamp string from a recording filename.
/// Returns empty string on malformed input.
fn recorded_at_iso_of(filename: &str) -> String {
    utc_date_and_iso_of(filename)
        .map(|(_, iso)| iso)
        .unwrap_or_default()
}

struct DateGroup {
    /// "Heute", "Gestern", or ISO date "YYYY-MM-DD".
    label: String,
    cases: Vec<UserCaseView>,
}

#[derive(Template)]
#[template(path = "my_cases.html")]
struct MyCasesTemplate {
    slug: String,
    groups: Vec<DateGroup>,
    total: usize,
    /// Number of cases that "Undo last delete" would restore. 0 hides the
    /// undo button entirely.
    undo_count: usize,
    /// True iff the session user is an admin — toggles full case_id display.
    is_admin: bool,
}

#[derive(Template)]
#[template(path = "case_page.html")]
struct CasePageTemplate {
    case_id: String,
    case_id_short: String,
    oneliner: Option<String>,
    /// Rendered document HTML (already passed through `md_to_html`). `Some`
    /// iff `document.md` exists at render time — template prioritises this
    /// over status/analyzing placeholders.
    document_html: Option<String>,
    recordings_count: usize,
    transcribed_count: usize,
    can_analyze: bool,
    llm_missing: bool,
    analyzing: bool,
    has_document: bool,
    is_admin: bool,
}

#[derive(Template)]
#[template(path = "case_recordings.html")]
struct CaseRecordingsTemplate {
    slug: String,
    case_id: String,
    case_id_short: String,
    oneliner: Option<String>,
    recordings: Vec<RecordingView>,
    transcribe_busy: bool,
    is_admin: bool,
}

/// Flags derived from filesystem state + config.
/// `can_analyze` covers both first analysis and re-analysis — same precondition
/// (all non-failed recordings transcribed, LLM configured, no analysis in
/// flight). `llm_missing` is shown to the user as an explanation when an
/// analysis would otherwise be possible but no LLM is configured.
struct CaseFlags {
    has_document: bool,
    analyzing: bool,
    can_analyze: bool,
    llm_missing: bool,
}

async fn compute_flags(
    case_dir: &Path,
    recordings: &[RecordingView],
    llm_configured: bool,
    worker_busy: bool,
) -> CaseFlags {
    let has_document = any_document_exists(case_dir).await;
    // Honest status: an input file alone does not mean a job is in flight.
    // The worker may be idle and the file an orphan from a crash. Page-level
    // self-heal (see `heal_orphans_if_idle`) re-enqueues those.
    let analyzing = !has_document && worker_busy && any_analysis_input_exists(case_dir).await;

    let non_failed: Vec<&RecordingView> = recordings.iter().filter(|r| !r.failed).collect();
    let all_transcribed =
        !non_failed.is_empty() && non_failed.iter().all(|r| r.transcript.is_some());

    let analyzable = !analyzing && all_transcribed;

    CaseFlags {
        has_document,
        analyzing,
        can_analyze: analyzable && llm_configured,
        llm_missing: analyzable && !llm_configured,
    }
}

/// True iff `analysis_input.json` exists. The worker removes it after a
/// successful document write, so existence implies a pending or in-flight job.
pub(crate) async fn any_analysis_input_exists(case_dir: &Path) -> bool {
    tokio::fs::try_exists(case_dir.join(ANALYSIS_INPUT_FILE))
        .await
        .unwrap_or(false)
}

/// True iff `document.md` exists.
pub(crate) async fn any_document_exists(case_dir: &Path) -> bool {
    tokio::fs::try_exists(case_dir.join(DOCUMENT_FILE))
        .await
        .unwrap_or(false)
}

/// Self-heal: if a worker is idle but orphans exist on disk for this user,
/// re-enqueue them. Page-load is the trigger; no cron, no periodic task.
/// Runs for both pipelines so a page-load on either view cleans both.
impl PipelineState {
    pub async fn heal_orphans_if_idle(&self, user_root: &Path, slug: &str) {
        if !self.analyze_busy.0.load(Ordering::Acquire) {
            analyze_recovery::enqueue_pending_for_user(user_root, &self.analyze_tx).await;
        }
        if !self.transcribe_busy.0.load(Ordering::Acquire) {
            transcribe_recovery::enqueue_pending_for_user(user_root, slug, &self.transcribe_tx)
                .await;
        }
    }
}

pub async fn handle_my_cases(
    user: AuthenticatedWebUser,
    State(config): State<Arc<Config>>,
    State(pipeline): State<PipelineState>,
    State(events_tx): State<EventSender>,
) -> Result<Html<String>, AppError> {
    let user_root = config.data_path.join(&user.slug);
    pipeline.heal_orphans_if_idle(&user_root, &user.slug).await;
    // Auto-analysis: hand every eligible case to the worker before we
    // render. The common case is "nothing to do" and costs a handful of
    // stat-calls per case; actual enqueues happen only when pre-conditions
    // flip (new transcripts in, stale document, ...).
    auto_trigger::try_enqueue_all_for_user(&user_root, &pipeline.analyze_tx, &config, &events_tx)
        .await;

    let busy = pipeline.analyze_busy.0.load(Ordering::Acquire);
    let cases = scan_user_cases(&config, &user.slug, busy).await;
    let total = cases.len();
    let groups = group_by_utc_date(cases);
    let undo_count = crate::routes::case_actions::summarize_latest_batch(&user_root)
        .await
        .map(|(_, n)| n)
        .unwrap_or(0);
    let is_admin = user.is_admin();
    MyCasesTemplate {
        slug: user.slug,
        groups,
        total,
        undo_count,
        is_admin,
    }
    .render()
    .map(Html)
    .map_err(|e| AppError::Internal(format!("Template render failed: {e}")))
}

/// GET /web/cases/{case_id}
///
/// Canonical case page. Renders the document inline if present; otherwise
/// shows status (analyzing / placeholder for empty / recordings-summary).
/// Action buttons (Analyze/Reanalyze/Reset/Delete) live here, not on the
/// recordings sub-page.
pub async fn handle_case_page(
    user: AuthenticatedWebUser,
    State(config): State<Arc<Config>>,
    State(pipeline): State<PipelineState>,
    State(events_tx): State<EventSender>,
    CaseIdPath(case_id): CaseIdPath,
) -> Result<Html<String>, AppError> {
    let user_root = config.data_path.join(&user.slug);
    pipeline.heal_orphans_if_idle(&user_root, &user.slug).await;

    let case_dir = locate_case_or_404(
        &user_root,
        &case_id,
        &user.slug,
        "case page (possible IDOR probe)",
    )
    .await?;
    // Auto-analysis trigger for deep-link navigation: same evaluation as
    // the list view. Document render below still wins the race if the
    // worker happens to finish synchronously.
    auto_trigger::try_enqueue(&case_dir, &pipeline.analyze_tx, &config, &events_tx).await;
    let case_id_str = case_id.to_string();
    info!(slug = %user.slug, case_id = %case_id, "case page viewed");

    // Read document first; if it's on disk we display it regardless of what
    // the `analyzing` flag would otherwise say. Resolves the narrow race
    // where the worker finishes between flag check and template render.
    let document_html = read_document(&case_dir)
        .await
        .map(|md| crate::analyze::render::md_to_html(&md));

    let recordings = scan_recordings(&case_dir).await;
    let oneliner = tokio::fs::read_to_string(case_dir.join("oneliner.txt"))
        .await
        .ok()
        .map(|s| s.trim().to_string())
        .filter(|s| !s.is_empty());

    let a_busy = pipeline.analyze_busy.0.load(Ordering::Acquire);
    let flags = compute_flags(&case_dir, &recordings, config.llm_configured(), a_busy).await;

    let recordings_count = recordings.len();
    let transcribed_count = recordings.iter().filter(|r| r.transcript.is_some()).count();
    let case_id_short = case_id_str.chars().take(8).collect();
    let is_admin = user.is_admin();

    CasePageTemplate {
        case_id: case_id_str,
        case_id_short,
        oneliner,
        document_html,
        recordings_count,
        transcribed_count,
        can_analyze: flags.can_analyze,
        llm_missing: flags.llm_missing,
        analyzing: flags.analyzing,
        has_document: flags.has_document,
        is_admin,
    }
    .render()
    .map(Html)
    .map_err(|e| AppError::Internal(format!("Template render failed: {e}")))
}

/// GET /web/cases/{case_id}/recordings
///
/// Read-only sub-page showing all `.m4a` + transcript pairs for the case.
/// Useful for power-users/admins; not part of the day-to-day workflow.
pub async fn handle_case_recordings(
    user: AuthenticatedWebUser,
    State(config): State<Arc<Config>>,
    State(pipeline): State<PipelineState>,
    CaseIdPath(case_id): CaseIdPath,
) -> Result<Html<String>, AppError> {
    let user_root = config.data_path.join(&user.slug);
    pipeline.heal_orphans_if_idle(&user_root, &user.slug).await;

    let case_dir = locate_case_or_404(
        &user_root,
        &case_id,
        &user.slug,
        "case recordings (possible IDOR probe)",
    )
    .await?;
    let case_id_str = case_id.to_string();
    info!(slug = %user.slug, case_id = %case_id, "case recordings viewed");

    let recordings = scan_recordings(&case_dir).await;
    let oneliner = tokio::fs::read_to_string(case_dir.join("oneliner.txt"))
        .await
        .ok()
        .map(|s| s.trim().to_string())
        .filter(|s| !s.is_empty());

    let t_busy = pipeline.transcribe_busy.0.load(Ordering::Acquire);
    let case_id_short = case_id_str.chars().take(8).collect();
    let is_admin = user.is_admin();

    CaseRecordingsTemplate {
        slug: user.slug,
        case_id: case_id_str,
        case_id_short,
        oneliner,
        recordings,
        transcribe_busy: t_busy,
        is_admin,
    }
    .render()
    .map(Html)
    .map_err(|e| AppError::Internal(format!("Template render failed: {e}")))
}

/// Locate a case directory under `<user_root>/<case_id>/`. Returns `None`
/// if the directory does not exist OR is soft-deleted (`.deleted` marker
/// present). Both are treated as 404 / IDOR probe by callers.
pub(crate) async fn locate_case(user_root: &Path, case_id: &str) -> Option<std::path::PathBuf> {
    let p = user_root.join(case_id);
    if !tokio::fs::try_exists(&p).await.unwrap_or(false) {
        return None;
    }
    if crate::paths::is_deleted(&p).await {
        return None;
    }
    Some(p)
}

/// Resolve a case directory for a handler, mapping any miss to
/// `AppError::NotFound("Case not found")` — matches the legacy 404 body
/// byte-for-byte. The `context` tag distinguishes log lines from the
/// different handlers (analyze, delete, reset, ...). Callers that need
/// a different not-found policy (silent skip in bulk ops) should keep
/// using `locate_case` directly.
pub(crate) async fn locate_case_or_404(
    user_root: &Path,
    case_id: &CaseId,
    user_slug: &str,
    context: &str,
) -> Result<std::path::PathBuf, AppError> {
    match locate_case(user_root, &case_id.to_string()).await {
        Some(p) => Ok(p),
        None => {
            warn!(
                slug = %user_slug,
                case_id = %case_id,
                context = %context,
                "case not found",
            );
            Err(AppError::NotFound("Case not found".into()))
        }
    }
}

/// Scan all of the given user's cases. Returned vec is sorted by most
/// recent recording filename (lexicographic ≈ chronological since
/// timestamps are ISO-8601), newest first. Soft-deleted cases (with
/// `.deleted` marker) are excluded.
async fn scan_user_cases(config: &Config, slug: &str, worker_busy: bool) -> Vec<UserCaseView> {
    let user_root = config.data_path.join(slug);
    let llm_configured = config.llm_configured();
    let mut cases = Vec::new();

    let mut entries = match tokio::fs::read_dir(&user_root).await {
        Ok(r) => r,
        Err(_) => return cases,
    };

    while let Ok(Some(entry)) = entries.next_entry().await {
        let Some((case_id, case_path)) = filter_valid_case_dir(entry).await else {
            continue;
        };
        if let Some(view) =
            compute_case_view(case_id, &case_path, llm_configured, worker_busy).await
        {
            cases.push(view);
        }
    }

    cases.sort_by(|a, b| b.most_recent.cmp(&a.most_recent));
    cases
}

/// Accept an entry only if it is a non-deleted directory whose name is
/// a valid UUID. Returns the (case_id-string, absolute path) tuple so
/// the caller does not need to recompute either. Non-UUID names are
/// logged at WARN level; other rejections are silent (common case).
async fn filter_valid_case_dir(entry: tokio::fs::DirEntry) -> Option<(String, std::path::PathBuf)> {
    let case_id = entry.file_name().into_string().ok()?;
    if uuid::Uuid::parse_str(&case_id).is_err() {
        warn!(case_id = %case_id, "Skipping non-UUID directory");
        return None;
    }
    let case_path = entry.path();
    if !case_path.is_dir() {
        return None;
    }
    if crate::paths::is_deleted(&case_path).await {
        return None;
    }
    Some((case_id, case_path))
}

/// Build a `UserCaseView` for a single case directory. Returns `None`
/// for empty cases (no recordings yet) so the caller can skip them.
async fn compute_case_view(
    case_id: String,
    case_path: &Path,
    llm_configured: bool,
    worker_busy: bool,
) -> Option<UserCaseView> {
    let recordings = scan_recordings(case_path).await;
    if recordings.is_empty() {
        return None;
    }

    let most_recent = recordings
        .last()
        .map(|r| r.filename.clone())
        .unwrap_or_default();
    let recordings_count = recordings.len();
    let non_failed_count = recordings.iter().filter(|r| !r.failed).count();
    let all_transcribed = non_failed_count > 0
        && recordings
            .iter()
            .filter(|r| !r.failed)
            .all(|r| r.transcript.is_some());

    let oneliner = tokio::fs::read_to_string(case_path.join("oneliner.txt"))
        .await
        .ok()
        .map(|s| s.trim().to_string())
        .filter(|s| !s.is_empty());

    let has_document = any_document_exists(case_path).await;
    let analyzing = !has_document && worker_busy && any_analysis_input_exists(case_path).await;
    let can_analyze = !analyzing && all_transcribed && llm_configured;

    let time_hms_utc = extract_hhmm_utc(&most_recent);
    let recorded_at_iso = recorded_at_iso_of(&most_recent);
    Some(UserCaseView {
        case_id,
        most_recent,
        time_hms_utc,
        recorded_at_iso,
        oneliner,
        recordings_count,
        analyzing,
        has_document,
        can_analyze,
    })
}