use axum::{ 
    extract::{Json, State}, 
    response::IntoResponse,
    http
};
use crate::structs::v3::PrometheusMetrics;
use prometheus::{ core::Collector, Encoder, GaugeVec, Registry, TextEncoder, proto::Metric};
use std::{collections::HashMap, fmt::Display, sync::{ Arc, MutexGuard }};
use crate::AppState;
use tracing::{ debug, error, info, warn, trace };
use crate::metrics::{MetricsProcesser, MetricsValueType};
use prometheus::opts;

#[derive(Clone)]
struct CloneableCollector(Arc<dyn Collector>);
impl CloneableCollector {
    fn from_boxed(collector: Box<dyn Collector>) -> Self {
        CloneableCollector(Arc::from(collector))
    }
    fn get_collector(&self) -> Box<dyn Collector> {
        Box::new(self.clone())
    }
    fn to_gauge_vec(&self) -> GaugeVec {
        let mut fam = self.0.collect()[0].clone();

        let metric_name = fam.take_name();
        let metric_help = fam.take_help();
        
        let lables = fam.get_metric().iter()
        .enumerate()
        .filter(|(id, _)| id == &0)
        .map(|(_, metric)| metric.get_label())
        .flat_map(|a| a.iter())
        .map(|a| a.get_name())
        .collect::<Vec<&str>>();
        
        let gv = GaugeVec::new(opts!(&metric_name, &metric_help), &lables).unwrap();

        for metric in fam.get_metric() {
            // gather values 
            let vals = metric.get_label()
            .iter()
            .map(|pair| pair.get_value())
            .collect::<Vec<&str>>();
            gv.with_label_values(&vals).set(metric.get_gauge().get_value());
        }
        gv
    }
}

impl Display for CloneableCollector {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> { 
        self.0.collect();
        write!(f, "{:#?}", self.0.collect())
    }
}

impl Collector for CloneableCollector {
    fn desc(&self) -> Vec<&prometheus::core::Desc> {
        self.0.desc()
    }
    
    fn collect(&self) -> Vec<prometheus::proto::MetricFamily> {
        self.0.collect()
    }
}

/// An `Update` endpoint
/// 
/// Used to registrate new metrics and to update already 
/// existing in local metrics `Registry`
/// 
/// # Usage
/// 
/// ``` bash
/// curl -X POST -d '...' 'http://127.0.0.1:9100/update' -d ...
/// ```
/// 
pub async fn update_metrics(
    State(state): State<Arc<AppState>>,
    Json(request) : Json<PrometheusMetrics<'_>>
) -> impl IntoResponse {
    trace!("post on /update");
    let service = &request.service_name;
    // let endpoint = &request.endpoint_name;
    // if request.with_device_status_and_module() {

    // } else {
        
    // }

    let mut metrics = Vec::new();

    for i in request.metrics {
        debug!("Processing metric: {:?}", &i);
        let metric_name = format!("{}_{}", service, &i.id);
        match MetricsProcesser::get_type_of_value(&i) {
            MetricsValueType::Array | 
            MetricsValueType::TaggedArray => {
                trace!("processing an array of metrics");
                //  ...
            },
            MetricsValueType::Number => {
                trace!("processing a number type of metric");
                let gauge = MetricsProcesser::gauge_from_number(
                    &i, 
                    &metric_name,
                    &i.desc.clone().unwrap_or_else(|| std::borrow::Cow::Borrowed(&i.id))
                );
                metrics.push(gauge);
                // if let Some(gauge) = gauge {
                //     match state.registry.lock() {
                //         Err(er) => {
                //             error!("Cannot lock Metric Registry due to {} ", er)
                //         },
                //         Ok(registry) => {
                //             //  todo: error handler
                //             if let Err(er) = update_or_insert_metric(
                //                 gauge, 
                //                 registry,
                //                 &metric_name
                //             ) {
                //                 error!("Update or insert metric crushed: {}", er);
                //                 return (http::StatusCode::INTERNAL_SERVER_ERROR, er.to_string())
                //             }
                //         },
                //     }
                // }
            },
            MetricsValueType::ArrayOfStrings => {
                trace!("processing an array of strings");
                warn!("String arrays are unsupported, ignoring ...");
            },
            _ => {
                trace!("processing unrecognized type of metric");
                warn!("Unrecognized metric type was supplied, ignoring ...");
            }
        }
    }
    for gauge in metrics {
        if let Some(gauge) = gauge {
                    match state.registry.lock() {
                        Err(er) => {
                            error!("Cannot lock Metric Registry due to {} ", er)
                        },
                        Ok(registry) => {
                            //  todo: error handler
                            if let Err(er) = update_or_insert_metric(
                                gauge, 
                                registry,
                            ) {
                                error!("Update or insert metric crushed: {}", er);
                                return (http::StatusCode::INTERNAL_SERVER_ERROR, er.to_string())
                            }
                        },
                    }
                }
    }
    (http::StatusCode::ACCEPTED, String::from("Ok"))
}

/// An `Metrics` endpoint
/// 
/// Needed in sharing current local metrics `Registry` state
/// and all stored metrics  
/// 
/// # Usage
/// 
/// ``` bash
/// curl -X GET 'http://127.0.0.1:9100/metrics'
/// ```
/// 
pub async fn metrics_handler(State(state): State<Arc<AppState>>) -> String {
    trace!("get on /metrics");
    let registry = state.registry.lock();
    
    debug!("registry mutex lock is {}", registry.is_ok());
    return match registry {
        Ok(registry) => {
            let encoder = TextEncoder::new();
            let mut buffer = Vec::new();
            let metric_families = registry.gather();
            // dbg!(&metric_families);
            debug!("vec of metric families - {:?}", &metric_families);
            
            encoder.encode(&metric_families, &mut buffer).unwrap();
            String::from_utf8(buffer).unwrap()
        },
        Err(er) => {
            format!("Cannot lock Metric Registry due to {} ", er)
        } 
    }
}

/// A function-registrator 
/// 
/// Registrates or updates metrics state in local 
/// `Registry`
/// 
pub fn update_or_insert_metric<'a>(
    metric: Box<dyn Collector>, 
    registry: MutexGuard<'a, Registry>,
    // metric_name: &str
) -> anyhow::Result<()> {
    trace!("fn update_or_insert_metric is running");
    let prod = CloneableCollector::from_boxed(metric);

    let family = registry.gather();

    let new_metric = prod.get_collector().collect();
    let new_metric_family = &new_metric[0];
    let new_metric_name = new_metric_family.get_name();

    if let Some(mut fam) = family.into_iter()
    .find(|fam| fam.get_name() == new_metric_name) {
        trace!("found exising metric. processing update ...");
        debug!("found metric : {:?}", &fam);
        let metric_name = fam.take_name();
        let metric_help = fam.take_help();
        let lables = fam.get_metric().iter()
        .enumerate()
        .filter(|(id, _)| id == &0)
        .map(|(_, metric)| metric.get_label())
        .flat_map(|a| a.iter())
        .map(|a| a.get_name())
        .collect::<Vec<&str>>();
        
        let gv = GaugeVec::new(opts!(&metric_name, &metric_help), &lables)?;

        for metric in fam.get_metric() {
            let vals = metric.get_label()
            .iter()
            .map(|pair| pair.get_value())
            .collect::<Vec<&str>>();
            gv.with_label_values(&vals).set(metric.get_gauge().get_value());
        }
        trace!("recreated metric as gauge vec {:?}", gv.collect());

        let new_vec = prod.to_gauge_vec().compare_with_old(&gv);
        
        registry.unregister(Box::new(gv))?;
        info!("Unregistered old metric!");
        registry.register(Box::new(new_vec))?;
        info!("Metric `{}` was re-registered!", new_metric_name);
    } else {
        match registry.register(prod.get_collector()) {
            Ok(_) => info!("Metric `{}` was registered!", new_metric_name),
            Err(er) => {
                error!("Cannot register new metric `{}` due to {}", new_metric_name, er);
                return Err(anyhow::Error::msg(
                    format!("Cannot register new metric `{}` due to {}", new_metric_name, er)
                ))
            },
        }
    }

    // match registry.register(prod.get_collector()) {
    //     Ok(_) => {
    //         info!("Metric `{}` was registered!", metric_name);
    //     },
    //     Err(er) => {
    //         // update or throw away
    //         match er {
    //             Error::AlreadyReg => {
    //                 trace!("processing already regged metric");
    //                 match registry.unregister(prod.get_collector()) {
    //                     Ok(_) => {
    //                         if let Err(er) = registry.register(prod.get_collector()) {
    //                             warn!("Cannot update metric `{}`", metric_name);
    //                             return Err(anyhow::Error::msg(
    //                                 format!("Cannot update metric `{}` due to {}", metric_name, er)
    //                             ))
    //                         } else {
    //                             info!("OK on metric `{}` update", metric_name);
    //                         }
    //                     },
    //                     Err(er) => {
    //                         error!("Cannot unregister metric `{}` due to {}", metric_name, er);
    //                         return Err(anyhow::Error::msg(
    //                             format!("Cannot unregister metric `{}` due to {}", metric_name, er)
    //                         ))
    //                     },
    //                 }
    //             },
    //             _ => {
    //                 error!("Cannot register new metric `{}` due to {}", metric_name, er);
    //                 return Err(anyhow::Error::msg(
    //                     format!("Cannot register new metric `{}` due to {}", metric_name, er)
    //                 ))
    //             }
    //         }
    //     },
    // }
    Ok(())
}


trait CompareGaugeVec {
    fn compare_with_old(self, old: &GaugeVec) -> Self;
}

impl CompareGaugeVec for GaugeVec {
    fn compare_with_old(mut self, old: &GaugeVec) -> Self {
        // old.
        let old_fam = old.collect();
        let new = self.collect();

        'outer: for old_fam in old_fam {
            for metric in old_fam.get_metric() {
                // labels for current old version of metric in vec
                let lables = get_hashmap_lables_from_metric(metric);
                dbg!(&lables);
                let value = metric.get_gauge().get_value();
                
                for new in &new {
                    for new_metric in new.get_metric() {
                        let new_lables = get_hashmap_lables_from_metric(new_metric);
                        dbg!(&new_lables);
                        if lables.len() != new_lables.len() {
                            error!("Trying to save invalid metric type. Reseting changes ...");
                            self = old.clone();
                            break 'outer;
                        } else {
                            match (lables.get("status"), new_lables.get("status")) {
                                (Some(&status), Some(_)) => {
                                    match (
                                            (lables.get("device"), lables.get("module")), 
                                            (new_lables.get("device"), new_lables.get("module")),
                                        ) {
                                            ((Some(&device), Some(&module)),
                                            (Some(&new_device), Some(&new_module))) => {
                                                /* */
                                                dbg!(1);
                                                if device != new_device || module != new_module {
                                                    dbg!(2);
                                                    self.with_label_values(&[device, module, status]).set(value);
                                                    // continue 'outer;
                                                }
                                            },
                                            ((Some(&device), None),
                                            (Some(&new_device), None)) => {
                                                /* */
                                                if device != new_device {
                                                    self.with_label_values(&[device, status]).set(value);
                                                    // continue 'outer;
                                                }
                                            },
                                            _ => { /* DEAD END */},
                                        }
                                },
                                _ => { /* DEAD END */ },
                            }
                        }
                    }
                }
            }
        }

        self
    }
}

fn get_hashmap_lables_from_metric(metric: &Metric) -> HashMap<&str, &str> {
    metric.get_label()
        .iter()
        .map(|pair| (pair.get_name(), pair.get_value()))
        .collect::<HashMap<&str, &str>>()
}