use crate::config::Settings;
use crate::meta_plugin::{MetaPlugin, MetaPluginResponse, MetaPluginType, SaveMetaFn};
use crate::modes::common::settings_meta_plugin_types;
use clap::Command;
use log::{debug, error, warn};
use std::collections::HashMap;

pub struct MetaService {
    save_meta: SaveMetaFn,
}

/// Sentinel plugin used as a placeholder when extracting plugins for parallel
/// execution. The original plugin is written back immediately after the threads
/// complete. Never leaks into the DB or visible state.
struct NullMetaPlugin;
impl MetaPlugin for NullMetaPlugin {
    fn meta_type(&self) -> MetaPluginType {
        MetaPluginType::Digest
    }
}

fn replace_plugin(plugins: &mut [Box<dyn MetaPlugin>], i: usize) -> Box<dyn MetaPlugin> {
    std::mem::replace(&mut plugins[i], Box::new(NullMetaPlugin))
}

/// Stores metadata entries from a plugin response via the save_meta callback.
fn store_plugin_response(response: &MetaPluginResponse, save_meta: &SaveMetaFn) {
    if let Ok(mut f) = save_meta.lock() {
        for meta_data in &response.metadata {
            f(&meta_data.name, &meta_data.value);
        }
    } else {
        warn!(
            "META_SERVICE: save_meta lock poisoned, dropping {} metadata entries",
            response.metadata.len()
        );
    }
}

impl MetaService {
    /// Creates a new MetaService with the given save_meta callback.
    ///
    /// All plugins created by this service will share this callback for
    /// persisting metadata. The callback is wrapped in Arc<Mutex<>> so it
    /// can be cloned into parallel-safe plugin threads.
    pub fn new(save_meta: SaveMetaFn) -> Self {
        Self { save_meta }
    }

    pub fn get_plugins(&self, cmd: &mut Command, settings: &Settings) -> Vec<Box<dyn MetaPlugin>> {
        debug!("META_SERVICE: get_plugins called");
        let meta_plugin_types: Vec<MetaPluginType> = settings_meta_plugin_types(cmd, settings);
        debug!("META_SERVICE: Meta plugin types from settings: {meta_plugin_types:?}");

        // Create plugins with their configuration and wire save_meta
        let meta_plugins: Vec<Box<dyn MetaPlugin>> = meta_plugin_types
            .iter()
            .filter_map(|meta_plugin_type| {
                debug!("META_SERVICE: Creating plugin: {meta_plugin_type:?}");

                // Get the plugin name using strum's Display implementation
                let plugin_name = meta_plugin_type.to_string();

                // Get options and outputs from settings
                let (options, outputs) = if let Some(meta_plugin_configs) = &settings.meta_plugins {
                    if let Some(config) = meta_plugin_configs.iter().find(|c| c.name == plugin_name)
                    {
                        // Convert options and outputs to the appropriate types
                        let options: std::collections::HashMap<String, serde_yaml::Value> = config
                            .options
                            .iter()
                            .map(|(k, v)| (k.clone(), v.clone()))
                            .collect();

                        let outputs: std::collections::HashMap<String, serde_yaml::Value> = config
                            .outputs
                            .iter()
                            .map(|(k, v)| (k.clone(), serde_yaml::Value::String(v.clone())))
                            .collect();

                        (Some(options), Some(outputs))
                    } else {
                        (None, None)
                    }
                } else {
                    (None, None)
                };

                match crate::meta_plugin::get_meta_plugin_with_save(
                    meta_plugin_type.clone(),
                    options,
                    outputs,
                    Some(self.save_meta.clone()),
                ) {
                    Ok(plugin) => Some(plugin),
                    Err(e) => {
                        log::warn!("META_SERVICE: Failed to create plugin {meta_plugin_type:?}: {e}, skipping");
                        None
                    }
                }
            })
            .collect();

        meta_plugins
    }

    pub fn initialize_plugins(&self, plugins: &mut [Box<dyn MetaPlugin>]) {
        // Check for duplicate output names before initializing plugins
        let mut output_names: std::collections::HashMap<String, Vec<String>> =
            std::collections::HashMap::new();

        for plugin in plugins.iter() {
            let plugin_name = plugin.meta_type().to_string();
            for (internal_name, output_config) in plugin.outputs() {
                let output_name = match output_config {
                    serde_yaml::Value::String(remapped_name) => remapped_name.clone(),
                    serde_yaml::Value::Bool(true) => internal_name.clone(),
                    serde_yaml::Value::Bool(false) => continue,
                    _ => internal_name.clone(),
                };

                if !matches!(output_config, serde_yaml::Value::Bool(false)) {
                    output_names
                        .entry(output_name)
                        .or_default()
                        .push(plugin_name.clone());
                }
            }
        }

        for (output_name, plugin_names) in &output_names {
            if plugin_names.len() > 1 {
                log::warn!(
                    "META_SERVICE: Output name '{}' is provided by multiple plugins: {}",
                    output_name,
                    plugin_names.join(", ")
                );
            }
        }

        // Partition into parallel-safe and sequential indices
        let (parallel_idx, sequential_idx): (Vec<usize>, Vec<usize>) = plugins
            .iter()
            .enumerate()
            .filter(|(_, p)| !p.is_finalized())
            .map(|(i, _)| i)
            .partition(|&i| plugins[i].parallel_safe());

        // Run parallel-safe plugins concurrently
        if !parallel_idx.is_empty() {
            // Extract plugins by unique index into a flat Vec indexed by position
            let mut parallel_plugins: Vec<Box<dyn MetaPlugin>> =
                Vec::with_capacity(parallel_idx.len());
            for &i in &parallel_idx {
                parallel_plugins.push(replace_plugin(plugins, i));
            }

            let (results, panicked): (Vec<(usize, MetaPluginResponse)>, Vec<usize>) =
                std::thread::scope(|s| {
                    let handles: Vec<_> = parallel_plugins
                        .iter_mut()
                        .map(|plugin| s.spawn(move || plugin.initialize()))
                        .collect();
                    let mut results = Vec::with_capacity(handles.len());
                    let mut panicked = Vec::new();
                    for (j, handle) in handles.into_iter().enumerate() {
                        match handle.join() {
                            Ok(response) => results.push((j, response)),
                            Err(e) => {
                                error!("META_SERVICE: Plugin panicked during initialize: {e:?}");
                                panicked.push(j);
                            }
                        }
                    }
                    (results, panicked)
                });

            for (j, response) in results {
                store_plugin_response(&response, &self.save_meta);
                let mut plugin = replace_plugin(&mut parallel_plugins, j);
                if response.is_finalized {
                    plugin.set_finalized(true);
                }
                plugins[parallel_idx[j]] = plugin;
            }
            for j in panicked {
                let mut plugin = replace_plugin(&mut parallel_plugins, j);
                plugin.set_finalized(true);
                plugins[parallel_idx[j]] = plugin;
            }
        }

        // Run sequential plugins
        for &i in &sequential_idx {
            let response = plugins[i].initialize();
            store_plugin_response(&response, &self.save_meta);
            if response.is_finalized {
                plugins[i].set_finalized(true);
            }
        }
    }

    pub fn process_chunk(&self, plugins: &mut [Box<dyn MetaPlugin>], chunk: &[u8]) {
        // Partition non-finalized plugins by parallel_safe
        let (parallel_idx, sequential_idx): (Vec<usize>, Vec<usize>) = plugins
            .iter()
            .enumerate()
            .filter(|(_, p)| !p.is_finalized())
            .map(|(i, _)| i)
            .partition(|&i| plugins[i].parallel_safe());

        // Run parallel-safe plugins concurrently on this chunk
        if !parallel_idx.is_empty() {
            let mut parallel_plugins: Vec<Box<dyn MetaPlugin>> =
                Vec::with_capacity(parallel_idx.len());
            for &i in &parallel_idx {
                parallel_plugins.push(replace_plugin(plugins, i));
            }

            let (results, panicked): (Vec<(usize, MetaPluginResponse)>, Vec<usize>) =
                std::thread::scope(|s| {
                    let handles: Vec<_> = parallel_plugins
                        .iter_mut()
                        .map(|plugin| s.spawn(move || plugin.update(chunk)))
                        .collect();
                    let mut results = Vec::with_capacity(handles.len());
                    let mut panicked = Vec::new();
                    for (j, handle) in handles.into_iter().enumerate() {
                        match handle.join() {
                            Ok(response) => results.push((j, response)),
                            Err(e) => {
                                error!("META_SERVICE: Plugin panicked during update: {e:?}");
                                panicked.push(j);
                            }
                        }
                    }
                    (results, panicked)
                });

            for (j, response) in results {
                store_plugin_response(&response, &self.save_meta);
                let mut plugin = replace_plugin(&mut parallel_plugins, j);
                if response.is_finalized {
                    plugin.set_finalized(true);
                }
                plugins[parallel_idx[j]] = plugin;
            }
            for j in panicked {
                let mut plugin = replace_plugin(&mut parallel_plugins, j);
                plugin.set_finalized(true);
                plugins[parallel_idx[j]] = plugin;
            }
        }

        // Run sequential plugins
        for &i in &sequential_idx {
            let response = plugins[i].update(chunk);
            store_plugin_response(&response, &self.save_meta);
            if response.is_finalized {
                plugins[i].set_finalized(true);
            }
        }
    }

    pub fn finalize_plugins(&self, plugins: &mut [Box<dyn MetaPlugin>]) {
        for meta_plugin in plugins.iter_mut() {
            if meta_plugin.is_finalized() {
                continue;
            }

            let response = meta_plugin.finalize();
            store_plugin_response(&response, &self.save_meta);

            if response.is_finalized {
                meta_plugin.set_finalized(true);
            }
        }
    }

    /// Collects initial metadata from environment variables and hostname.
    pub fn collect_initial_meta(&self) -> HashMap<String, String> {
        Self::collect_initial_meta_static()
    }

    /// Static version of collect_initial_meta for use without a MetaService instance.
    pub fn collect_initial_meta_static() -> HashMap<String, String> {
        let mut item_meta: HashMap<String, String> = crate::modes::common::get_meta_from_env();

        if let Ok(hostname) = gethostname::gethostname().into_string()
            && !item_meta.contains_key("hostname")
        {
            item_meta.insert("hostname".to_string(), hostname);
        }
        item_meta
    }
}