//! The paced workspace walk.
//!
//! Targets are flattened into one ordered list of (account, workspace). The
//! walk is sequential with 500 ms pacing. Per workspace two requests run at
//! once: Zen for balance and Go for limits. Fresh cache skips the network.

use std::time::Duration;

use chrono::Utc;

use crate::cache::{self, CachedRecord};
use crate::client::{self, HttpClient};
use crate::model::{AccountReport, Balance, Limits, ReportStatus};
use crate::scrape;

/// One fetch target: an account and one workspace of it, with the cookie.
#[derive(Clone)]
pub struct Target {
    pub account: String,
    pub workspace: String,
    pub cookie: String,
}

/// Resolved pipeline options from the CLI.
#[derive(Clone)]
pub struct FetchOptions {
    pub ttl_secs: u32,
    pub timeout_secs: u64,
    pub retries: u8,
    pub force_refresh: bool,
    pub no_cache: bool,
    pub workspace_pace_ms: u64,
    pub account_filter: Vec<String>,
    pub workspace_filter: Vec<String>,
    pub user_agent: String,
}

/// Build the target list from the config, applying CLI filters.
pub fn targets(cfg: &crate::config::Config, opts: &FetchOptions) -> Vec<Target> {
    let mut out = Vec::new();
    for acct in &cfg.account {
        if !opts.account_filter.is_empty() && !opts.account_filter.contains(&acct.name) {
            continue;
        }
        for ws in acct.workspace_ids() {
            if !opts.workspace_filter.is_empty() && !opts.workspace_filter.contains(&ws) {
                continue;
            }
            out.push(Target {
                account: acct.name.clone(),
                workspace: ws,
                cookie: acct.cookie.clone(),
            });
        }
    }
    out
}

/// Walk all targets. Returns one report per target, in config order.
pub async fn run(cfg: &crate::config::Config, opts: &FetchOptions) -> anyhow::Result<Vec<AccountReport>> {
    let http = HttpClient::new(opts.user_agent.clone(), opts.timeout_secs, opts.retries)?;
    let targets = targets(cfg, opts);

    let mut reports = Vec::with_capacity(targets.len());
    for (i, tgt) in targets.iter().enumerate() {
        let report = fetch_target(tgt, opts, &http).await;
        reports.push(report);

        // Pace before the next workspace. Do not pace after the last.
        if i + 1 < targets.len() && opts.workspace_pace_ms > 0 {
            tokio::time::sleep(Duration::from_millis(opts.workspace_pace_ms)).await;
        }
    }
    Ok(reports)
}

/// Fetch one target. Cache short-circuits the network.
async fn fetch_target(tgt: &Target, opts: &FetchOptions, http: &HttpClient) -> AccountReport {
    // Cache hit path.
    if !opts.force_refresh && !opts.no_cache {
        if let Some(rec) = cache::read(&tgt.account, &tgt.workspace, opts.ttl_secs) {
            let mut r = rec.report;
            r.status = ReportStatus::Cached;
            return r;
        }
    }

    // Network path. Fire Zen and Go at once.
    let zen_url = client::zen_url(&tgt.workspace);
    let go_url = client::go_url(&tgt.workspace);
    let (zen_res, go_res) = tokio::join!(
        http.get_text(&zen_url, &tgt.cookie),
        http.get_text(&go_url, &tgt.cookie),
    );

    let fetched_at = Some(Utc::now().to_rfc3339());
    let balance = match &zen_res {
        Ok(html) => match scrape::parse_zen_balance(html) {
            Ok(b) => Some(b),
            Err(e) => {
                tracing::warn!(account = %tgt.account, workspace = %tgt.workspace, error = %e, "zen parse failed");
                None
            }
        },
        Err(e) => {
            tracing::warn!(account = %tgt.account, workspace = %tgt.workspace, error = %e, "zen fetch failed");
            None
        }
    };
    let limits = match &go_res {
        Ok(html) => match scrape::parse_go_limits(html) {
            Ok(l) => Some(l),
            Err(e) => {
                tracing::warn!(account = %tgt.account, workspace = %tgt.workspace, error = %e, "go parse failed");
                None
            }
        },
        Err(e) => {
            tracing::warn!(account = %tgt.account, workspace = %tgt.workspace, error = %e, "go fetch failed");
            None
        }
    };

    // Decide the status. RateLimited and Timeout take priority over generic
    // Error so callers can react.
    let status = report_status(&zen_res, &go_res, limits.as_ref(), balance.as_ref());

    let report = AccountReport {
        account: tgt.account.clone(),
        workspace: tgt.workspace.clone(),
        fetched_at,
        status: status.clone(),
        limits: limits.clone(),
        balance: balance.clone(),
    };

    // Write cache only on a clean Ok, so errors never poison the cache.
    if status == ReportStatus::Ok {
        let record = CachedRecord {
            report: report.clone(),
            go_etag: None,
            go_last_modified: None,
            zen_etag: None,
            zen_last_modified: None,
        };
        if let Err(e) = cache::write(&tgt.account, &tgt.workspace, &record) {
            tracing::warn!(error = %e, "cache write failed");
        }
    }

    report
}

/// Fold the two fetch results into one status.
fn report_status(
    zen: &Result<String, crate::error::FetchError>,
    go: &Result<String, crate::error::FetchError>,
    limits: Option<&Limits>,
    balance: Option<&Balance>,
) -> ReportStatus {
    use crate::error::FetchError;
    for r in [zen, go] {
        match r {
            Err(FetchError::RateLimited) => return ReportStatus::RateLimited,
            Err(FetchError::Timeout) => return ReportStatus::Timeout,
            Err(FetchError::Status { status, .. }) if *status == 429 => {
                return ReportStatus::RateLimited;
            }
            _ => {}
        }
    }
    for r in [zen, go] {
        if let Err(e) = r {
            if limits.is_none() && balance.is_none() {
                return ReportStatus::Error(e.to_string());
            }
            return ReportStatus::Error(e.to_string());
        }
    }
    if limits.is_some() || balance.is_some() {
        ReportStatus::Ok
    } else {
        ReportStatus::Error("no limits or balance parsed".to_string())
    }
}