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

use askama::Template;
use axum::body::Body;
use axum::extract::{Path as AxumPath, State};
use axum::http::header;
use axum::response::{Html, Response};
use tracing::warn;

use crate::config::Config;
use crate::error::AppError;
use crate::routes::user_web::any_document_exists;

pub(crate) struct RecordingView {
    pub(crate) filename: String,
    pub(crate) transcript: Option<String>,
    /// True if the file has been renamed to `<ts>.m4a.failed` by the worker
    /// after a non-recoverable ffmpeg or whisper error.
    pub(crate) failed: bool,
}

struct CaseView {
    user_slug: String,
    case_id: String,
    case_id_short: String,
    has_document: bool,
    most_recent: String,
    oneliner: Option<String>,
    recordings: Vec<RecordingView>,
}

#[derive(Template)]
#[template(path = "cases.html")]
struct CasesTemplate {
    cases: Vec<CaseView>,
}

pub async fn handle_case_list(
    State(config): State<Arc<Config>>,
) -> Result<Html<String>, AppError> {
    let cases = scan_cases(&config.data_path).await;
    let template = CasesTemplate { cases };
    template
        .render()
        .map(Html)
        .map_err(|e| AppError::Internal(format!("Template render failed: {e}")))
}

pub async fn handle_audio(
    State(config): State<Arc<Config>>,
    AxumPath((user, case_id, filename)): AxumPath<(String, String, String)>,
) -> Result<Response, AppError> {
    validate_user_slug(&user)?;
    uuid::Uuid::parse_str(&case_id)
        .map_err(|_| AppError::BadRequest("Invalid case_id (not a UUID)".into()))?;
    validate_filename(&filename)?;

    let case_path = crate::paths::case_dir(&config.data_path, &user, &case_id);
    if crate::paths::is_deleted(&case_path).await {
        return Err(AppError::NotFound("Audio file not found".into()));
    }
    let file_path = case_path.join(&filename);
    if !tokio::fs::try_exists(&file_path).await.unwrap_or(false) {
        return Err(AppError::NotFound("Audio file not found".into()));
    }

    let bytes = tokio::fs::read(&file_path).await?;

    Response::builder()
        .header(header::CONTENT_TYPE, "audio/mp4")
        .body(Body::from(bytes))
        .map_err(|e| AppError::Internal(e.to_string()))
}

fn validate_user_slug(user: &str) -> Result<(), AppError> {
    if user.is_empty() || user.contains('/') || user.contains('\\') || user.contains("..") {
        return Err(AppError::BadRequest("Invalid user slug".into()));
    }
    Ok(())
}

fn validate_filename(filename: &str) -> Result<(), AppError> {
    let ok_suffix = filename.ends_with(".m4a") || filename.ends_with(".m4a.failed");
    if !ok_suffix
        || filename.contains('/')
        || filename.contains('\\')
        || filename.contains("..")
    {
        return Err(AppError::BadRequest("Invalid filename".into()));
    }
    Ok(())
}

/// Scan the data directory for all cases across all users.
/// Silently skips invalid entries so a single broken directory does not break the page.
async fn scan_cases(data_path: &Path) -> Vec<CaseView> {
    let mut cases = Vec::new();

    let mut users = match tokio::fs::read_dir(data_path).await {
        Ok(r) => r,
        Err(_) => return cases, // data_path may not exist yet
    };

    while let Ok(Some(user_entry)) = users.next_entry().await {
        let user_slug = match user_entry.file_name().into_string() {
            Ok(s) => s,
            Err(_) => continue,
        };
        if validate_user_slug(&user_slug).is_err() {
            continue;
        }
        if !user_entry.path().is_dir() {
            continue;
        }

        let mut case_entries = match tokio::fs::read_dir(user_entry.path()).await {
            Ok(r) => r,
            Err(_) => continue,
        };

        while let Ok(Some(case_entry)) = case_entries.next_entry().await {
            let case_id = match case_entry.file_name().into_string() {
                Ok(s) => s,
                Err(_) => continue,
            };
            if uuid::Uuid::parse_str(&case_id).is_err() {
                warn!(case_id = %case_id, "Skipping non-UUID directory");
                continue;
            }
            if !case_entry.path().is_dir() {
                continue;
            }

            let case_path = case_entry.path();
            if crate::paths::is_deleted(&case_path).await {
                continue;
            }
            let recordings = scan_recordings(&case_path).await;
            if recordings.is_empty() {
                continue;
            }

            let most_recent = recordings
                .last()
                .map(|r| r.filename.clone())
                .unwrap_or_default();
            let case_id_short = case_id.chars().take(8).collect();
            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;

            cases.push(CaseView {
                user_slug: user_slug.clone(),
                case_id,
                case_id_short,
                has_document,
                most_recent,
                oneliner,
                recordings,
            });
        }
    }

    // Most recent case first.
    cases.sort_by(|a, b| b.most_recent.cmp(&a.most_recent));
    cases
}

pub(crate) async fn scan_recordings(case_dir: &Path) -> Vec<RecordingView> {
    let mut recordings = Vec::new();
    let mut entries = match tokio::fs::read_dir(case_dir).await {
        Ok(r) => r,
        Err(_) => return recordings,
    };

    while let Ok(Some(entry)) = entries.next_entry().await {
        let filename = match entry.file_name().into_string() {
            Ok(s) => s,
            Err(_) => continue,
        };
        let failed = filename.ends_with(".m4a.failed");
        let is_audio = filename.ends_with(".m4a") || failed;
        if !is_audio {
            continue;
        }
        // Transcript naming uses the original `<ts>.m4a` stem in both cases
        // (failed recordings never produced one, but the lookup still works).
        let stem_path = case_dir.join(filename.trim_end_matches(".failed"));
        let transcript_path = stem_path.with_extension("transcript.txt");
        let transcript = tokio::fs::read_to_string(&transcript_path).await.ok();
        recordings.push(RecordingView {
            filename,
            transcript,
            failed,
        });
    }

    recordings.sort_by(|a, b| a.filename.cmp(&b.filename));
    recordings
}