//! Aliyun DashScope file-trans ASR client (qwen3-asr-flash-filetrans).
//!
//! The dashscope async transcription flow has two steps:
//!   1. POST  https://dashscope.aliyuncs.com/api/v1/services/audio/asr/transcription
//!      header `X-DashScope-Async: enable`
//!      body   { model, input: { file_urls: [audio_url] }, parameters: {...} }
//!      => returns task_id
//!   2. GET   https://dashscope.aliyuncs.com/api/v1/tasks/{task_id}
//!      poll until task_status in {SUCCEEDED, FAILED}
//!
//! On success the response carries one or more `transcription_url`s pointing
//! at JSON files containing the recognized sentences.  We download the first
//! one and concatenate the sentence texts.

use std::time::Duration;

use serde::{Deserialize, Serialize};
use serde_json::{json, Value};
use thiserror::Error;
use tokio::time::sleep;

const SUBMIT_URL: &str =
    "https://dashscope.aliyuncs.com/api/v1/services/audio/asr/transcription";
const TASK_URL_PREFIX: &str = "https://dashscope.aliyuncs.com/api/v1/tasks/";

#[derive(Debug, Error)]
pub enum AsrError {
    #[error("missing api key")]
    MissingApiKey,
    #[error("http: {0}")]
    Http(#[from] reqwest::Error),
    #[error("dashscope: {0}")]
    Api(String),
    #[error("timeout waiting for asr task")]
    Timeout,
    #[error("json: {0}")]
    Json(#[from] serde_json::Error),
}

#[derive(Debug, Deserialize, Serialize, Clone)]
pub struct AsrSentence {
    #[serde(default)]
    pub text: String,
    #[serde(default)]
    pub begin_time: Option<i64>,
    #[serde(default)]
    pub end_time: Option<i64>,
}

#[derive(Debug, Serialize)]
pub struct AsrResult {
    pub success: bool,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub text: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub sentences: Option<Vec<AsrSentence>>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub error: Option<String>,
}

pub async fn transcribe(
    audio_url: &str,
    api_key: &str,
    model: &str,
) -> Result<AsrResult, AsrError> {
    if api_key.trim().is_empty() {
        return Err(AsrError::MissingApiKey);
    }
    let client = reqwest::Client::builder()
        .timeout(Duration::from_secs(60))
        .build()?;

    // 1) submit
    let submit_body = json!({
        "model": model,
        "input": { "file_urls": [audio_url] },
        "parameters": {}
    });
    let submit: Value = client
        .post(SUBMIT_URL)
        .bearer_auth(api_key)
        .header("X-DashScope-Async", "enable")
        .json(&submit_body)
        .send()
        .await?
        .json()
        .await?;
    let task_id = submit
        .pointer("/output/task_id")
        .and_then(Value::as_str)
        .ok_or_else(|| AsrError::Api(format!("submit: no task_id, raw={submit}")))?
        .to_string();

    // 2) poll
    let max_polls = 60; // ~5 min @ 5s
    let mut poll_resp: Value = Value::Null;
    let mut succeeded = false;
    for _ in 0..max_polls {
        sleep(Duration::from_secs(5)).await;
        poll_resp = client
            .get(format!("{TASK_URL_PREFIX}{task_id}"))
            .bearer_auth(api_key)
            .send()
            .await?
            .json()
            .await?;
        let status = poll_resp
            .pointer("/output/task_status")
            .and_then(Value::as_str)
            .unwrap_or("");
        match status {
            "SUCCEEDED" => { succeeded = true; break; }
            "FAILED" | "UNKNOWN" => {
                let msg = poll_resp
                    .pointer("/output/message")
                    .and_then(Value::as_str)
                    .unwrap_or("FAILED");
                return Err(AsrError::Api(msg.to_string()));
            }
            _ => continue,
        }
    }
    if !succeeded {
        return Err(AsrError::Timeout);
    }

    // 3) fetch transcription file
    let trans_url = poll_resp
        .pointer("/output/results/0/transcription_url")
        .and_then(Value::as_str)
        .ok_or_else(|| AsrError::Api(format!("no transcription_url, raw={poll_resp}")))?
        .to_string();
    let trans_json: Value = client.get(&trans_url).send().await?.json().await?;

    // dashscope transcription file shape:
    //   { "transcripts": [{ "text": "...", "sentences": [{text, begin_time, end_time}, ...] }] }
    let mut full_text = String::new();
    let mut sentences = Vec::<AsrSentence>::new();
    if let Some(transcripts) = trans_json.get("transcripts").and_then(Value::as_array) {
        for t in transcripts {
            if let Some(text) = t.get("text").and_then(Value::as_str) {
                if !full_text.is_empty() { full_text.push('\n'); }
                full_text.push_str(text);
            }
            if let Some(arr) = t.get("sentences").and_then(Value::as_array) {
                for s in arr {
                    sentences.push(AsrSentence {
                        text: s.get("text").and_then(Value::as_str).unwrap_or("").to_string(),
                        begin_time: s.get("begin_time").and_then(Value::as_i64),
                        end_time: s.get("end_time").and_then(Value::as_i64),
                    });
                }
            }
        }
    } else if let Some(text) = trans_json.get("text").and_then(Value::as_str) {
        full_text.push_str(text);
    }

    Ok(AsrResult {
        success: true,
        text: Some(full_text),
        sentences: if sentences.is_empty() { None } else { Some(sentences) },
        error: None,
    })
}