/*
 * SPDX-FileCopyrightText: 2020 Stalwart Labs LLC <hello@stalw.art>
 *
 * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
 */

use crate::task_manager::{TaskFailureType, TaskResult};
use common::{
    Server,
    ipc::{BroadcastEvent, RegistryChange},
    manager::{SPAM_CLASSIFIER_KEY, SPAM_TRAINER_KEY, fetch_resource},
};
use registry::{
    schema::{
        enums::TaskSpamFilterMaintenanceType,
        prelude::{Object, ObjectInner, ObjectType},
        structs::{
            HttpLookup, MemoryLookupKey, SpamDnsblServer, SpamFileExtension, SpamRule, SpamTag,
            TaskSpamFilterMaintenance,
        },
    },
    types::{EnumImpl, ObjectImpl},
};
use spam_filter::modules::classifier::SpamClassifier;
use std::time::{Duration, Instant};
use store::{
    RegistryStore,
    ahash::AHashMap,
    registry::write::{RegistryWrite, RegistryWriteResult},
};
use trc::{SpamEvent, Value};

pub(crate) trait SpamFilterMaintenanceTask: Sync + Send {
    fn spam_filter_maintenance(
        &self,
        task: &TaskSpamFilterMaintenance,
    ) -> impl Future<Output = TaskResult> + Send;
}

impl SpamFilterMaintenanceTask for Server {
    async fn spam_filter_maintenance(&self, task: &TaskSpamFilterMaintenance) -> TaskResult {
        match spam_filter_maintenance(self, task).await {
            Ok(result) => result,
            Err(err) => {
                let result = TaskResult::temporary(err.to_string());
                trc::error!(err.details("Failed to perform spam filter maintenance task"));
                result
            }
        }
    }
}

async fn spam_filter_maintenance(
    server: &Server,
    task: &TaskSpamFilterMaintenance,
) -> trc::Result<TaskResult> {
    match task.maintenance_type {
        TaskSpamFilterMaintenanceType::Train => {
            if !server.inner.ipc.train_task_controller.is_running() {
                Box::pin(server.spam_train(false)).await?;
            }
        }
        TaskSpamFilterMaintenanceType::Retrain => {
            if !server.inner.ipc.train_task_controller.is_running() {
                Box::pin(server.spam_train(true)).await?;
            }
        }
        TaskSpamFilterMaintenanceType::Reset => {
            for key in [SPAM_CLASSIFIER_KEY, SPAM_TRAINER_KEY] {
                server.blob_store().delete_blob(key).await?;
            }
        }
        TaskSpamFilterMaintenanceType::Abort => {
            if server.inner.ipc.train_task_controller.is_running() {
                server.inner.ipc.train_task_controller.stop();
            }
        }
        TaskSpamFilterMaintenanceType::UpdateRules => {
            return update_spam_rules(server).await;
        }
    }

    Ok(TaskResult::Success(vec![]))
}

struct RuleUpdateError {
    typ: TaskFailureType,
    reason: String,
}

#[derive(Default)]
struct Rules {
    rules: Vec<SpamRule>,
    dnsbls: Vec<SpamDnsblServer>,
    tags: Vec<SpamTag>,
    http_lookups: Vec<HttpLookup>,
    key_lookups: Vec<MemoryLookupKey>,
    file_exts: Vec<SpamFileExtension>,
}

trait UpstreamObject: ObjectImpl + PartialEq + From<Object> + Into<ObjectInner> {
    fn replacement_for(self, _local: &Self) -> Option<Self> {
        Some(self)
    }
}

impl UpstreamObject for SpamRule {
    fn replacement_for(mut self, local: &Self) -> Option<Self> {
        self.set_enable(local.enable());
        Some(self)
    }
}

impl UpstreamObject for SpamDnsblServer {
    fn replacement_for(mut self, local: &Self) -> Option<Self> {
        self.set_enable(local.enable());
        Some(self)
    }
}

impl UpstreamObject for HttpLookup {
    fn replacement_for(mut self, local: &Self) -> Option<Self> {
        self.enable = local.enable;
        Some(self)
    }
}

impl UpstreamObject for SpamTag {
    fn replacement_for(self, _local: &Self) -> Option<Self> {
        None
    }
}

impl UpstreamObject for MemoryLookupKey {}

impl UpstreamObject for SpamFileExtension {}

struct RuleUpdateResult {
    object_type: ObjectType,
    added: usize,
    updated: usize,
    unchanged: usize,
    failed: usize,
}

impl RuleUpdateResult {
    fn new(object_type: ObjectType) -> Self {
        RuleUpdateResult {
            object_type,
            added: 0,
            updated: 0,
            unchanged: 0,
            failed: 0,
        }
    }

    fn has_changes(&self) -> bool {
        self.added + self.updated > 0
    }
}

async fn update_spam_rules(server: &Server) -> trc::Result<TaskResult> {
    let started = Instant::now();
    let rules = match fetch_spam_rules(server).await {
        Ok(rules) => rules,
        Err(err) => {
            return Ok(TaskResult::Failure {
                typ: err.typ,
                message: err.reason,
                max_attempts: None,
            });
        }
    };

    let registry = server.registry();
    let settings = [
        apply_upstream(registry, rules.rules).await?,
        apply_upstream(registry, rules.dnsbls).await?,
        apply_upstream(registry, rules.tags).await?,
        apply_upstream(registry, rules.file_exts).await?,
    ];
    let lookups = [
        apply_upstream(registry, rules.http_lookups).await?,
        apply_upstream(registry, rules.key_lookups).await?,
    ];

    let mut reload_errors = Vec::new();
    for object in [
        settings
            .iter()
            .any(RuleUpdateResult::has_changes)
            .then_some(ObjectType::SpamRule),
        lookups
            .iter()
            .any(RuleUpdateResult::has_changes)
            .then_some(ObjectType::MemoryLookupKey),
    ]
    .into_iter()
    .flatten()
    {
        if let Err(reason) = reload_and_broadcast(server, object).await {
            reload_errors.push(reason);
        }
    }
    let failed: usize = settings
        .iter()
        .chain(&lookups)
        .map(|result| result.failed)
        .sum();

    trc::event!(
        Spam(SpamEvent::RulesUpdated),
        Details = settings
            .into_iter()
            .chain(lookups)
            .map(|result| {
                Value::Array(vec![
                    Value::String(result.object_type.as_str().into()),
                    Value::from(result.added),
                    Value::from(result.updated),
                    Value::from(result.unchanged),
                    Value::from(result.failed),
                ])
            })
            .collect::<Vec<_>>(),
        Elapsed = started.elapsed(),
    );

    if !reload_errors.is_empty() {
        Ok(TaskResult::permanent(format!(
            "Spam rules were stored but not activated ({}); fix the logged errors and run Reload settings",
            reload_errors.join("; ")
        )))
    } else if failed > 0 {
        Ok(TaskResult::permanent(format!(
            "{failed} spam filter objects failed to import or update"
        )))
    } else {
        Ok(TaskResult::Success(vec![]))
    }
}

async fn reload_and_broadcast(server: &Server, object: ObjectType) -> Result<(), String> {
    match Box::pin(server.reload_registry(RegistryChange::Reload(object))).await {
        Ok(result) => {
            result.log();
            if result.has_errors() {
                return Err(format!("{} configuration errors", result.errors.len()));
            }
            server
                .cluster_broadcast(BroadcastEvent::RegistryChange(RegistryChange::Reload(
                    object,
                )))
                .await;
            Ok(())
        }
        Err(err) => {
            let reason = err.to_string();
            trc::error!(err.details("Failed to reload registry after updating spam rules"));
            Err(reason)
        }
    }
}

async fn apply_upstream<T: UpstreamObject>(
    registry: &RegistryStore,
    objects: Vec<T>,
) -> trc::Result<RuleUpdateResult> {
    let mut result = RuleUpdateResult::new(T::OBJECT);

    for upstream in objects {
        let upstream = Object::from(upstream);
        let existing_id = match registry.write(RegistryWrite::insert(&upstream)).await? {
            RegistryWriteResult::Success(_) => {
                result.added += 1;
                continue;
            }
            RegistryWriteResult::PrimaryKeyConflict { existing_id, .. }
                if existing_id.object() == T::OBJECT =>
            {
                existing_id
            }
            RegistryWriteResult::PrimaryKeyConflict { .. } => {
                result.unchanged += 1;
                continue;
            }
            _ => {
                result.failed += 1;
                continue;
            }
        };

        let Some(local) = registry.get(existing_id).await? else {
            result.failed += 1;
            continue;
        };
        let revision = local.revision;
        let local = T::from(local);
        let Some(replacement) = T::from(upstream)
            .replacement_for(&local)
            .filter(|replacement| replacement != &local)
        else {
            result.unchanged += 1;
            continue;
        };

        let replacement = Object::from(replacement);
        let local = Object::with_revision(local.into(), revision);
        match registry
            .write(RegistryWrite::update(
                existing_id.id(),
                &replacement,
                &local,
            ))
            .await?
        {
            RegistryWriteResult::Success(_) => result.updated += 1,
            _ => result.failed += 1,
        }
    }

    Ok(result)
}

async fn fetch_spam_rules(server: &Server) -> Result<Rules, RuleUpdateError> {
    let Some(rules_url) = server.core.spam.spam_rules_url.as_ref() else {
        return Err(RuleUpdateError {
            typ: TaskFailureType::Permanent,
            reason: "Spam rules resource URL not configured".to_string(),
        });
    };
    let rules_json: AHashMap<String, Vec<serde_json::Value>> =
        fetch_resource(rules_url, None, Duration::from_secs(60), 1024 * 500)
            .await
            .map_err(|reason| RuleUpdateError {
                typ: TaskFailureType::Temporary,
                reason,
            })
            .and_then(|bytes| {
                serde_json::from_slice(&bytes).map_err(|err| RuleUpdateError {
                    typ: TaskFailureType::Permanent,
                    reason: format!("Failed to parse spam rules JSON: {err}"),
                })
            })?;

    let mut rules = Rules::default();
    for (object_type, values) in rules_json {
        let Some(object_type) = ObjectType::parse(&object_type) else {
            return Err(RuleUpdateError {
                typ: TaskFailureType::Permanent,
                reason: format!("Invalid object type in spam rules JSON: {object_type}"),
            });
        };

        match object_type {
            ObjectType::SpamRule => {
                rules.rules = values
                    .into_iter()
                    .map(|value| {
                        serde_json::from_value(value).map_err(|err| RuleUpdateError {
                            typ: TaskFailureType::Permanent,
                            reason: format!("Failed to parse spam rule: {err}"),
                        })
                    })
                    .collect::<Result<Vec<SpamRule>, RuleUpdateError>>()?;
            }
            ObjectType::SpamDnsblServer => {
                rules.dnsbls = values
                    .into_iter()
                    .map(|value| {
                        serde_json::from_value(value).map_err(|err| RuleUpdateError {
                            typ: TaskFailureType::Permanent,
                            reason: format!("Failed to parse DNSBL server: {err}"),
                        })
                    })
                    .collect::<Result<Vec<SpamDnsblServer>, RuleUpdateError>>()?;
            }
            ObjectType::SpamTag => {
                rules.tags = values
                    .into_iter()
                    .map(|value| {
                        serde_json::from_value(value).map_err(|err| RuleUpdateError {
                            typ: TaskFailureType::Permanent,
                            reason: format!("Failed to parse spam tag: {err}"),
                        })
                    })
                    .collect::<Result<Vec<SpamTag>, RuleUpdateError>>()?;
            }
            ObjectType::HttpLookup => {
                rules.http_lookups = values
                    .into_iter()
                    .map(|value| {
                        serde_json::from_value(value).map_err(|err| RuleUpdateError {
                            typ: TaskFailureType::Permanent,
                            reason: format!("Failed to parse HTTP lookup: {err}"),
                        })
                    })
                    .collect::<Result<Vec<HttpLookup>, RuleUpdateError>>()?;
            }
            ObjectType::MemoryLookupKey => {
                rules.key_lookups = values
                    .into_iter()
                    .map(|value| {
                        serde_json::from_value(value).map_err(|err| RuleUpdateError {
                            typ: TaskFailureType::Permanent,
                            reason: format!("Failed to parse memory lookup key: {err}"),
                        })
                    })
                    .collect::<Result<Vec<MemoryLookupKey>, RuleUpdateError>>()?;
            }
            ObjectType::SpamFileExtension => {
                rules.file_exts = values
                    .into_iter()
                    .map(|value| {
                        serde_json::from_value(value).map_err(|err| RuleUpdateError {
                            typ: TaskFailureType::Permanent,
                            reason: format!("Failed to parse spam file extension: {err}"),
                        })
                    })
                    .collect::<Result<Vec<SpamFileExtension>, RuleUpdateError>>()?;
            }
            _ => {
                return Err(RuleUpdateError {
                    typ: TaskFailureType::Permanent,
                    reason: format!("Unsupported object type in spam rules: {object_type:?}"),
                });
            }
        }
    }

    Ok(rules)
}