//! API helpers for get-or-create and get-and-modify patterns
//!
//! [`Api::entry`] is the primary entry point for this API.

// Import used in docs
#[allow(unused_imports)] use std::collections::HashMap;
use std::fmt::Debug;

use crate::{Api, Error, Result};
use kube_core::{params::PostParams, Resource};
use serde::{de::DeserializeOwned, Serialize};

impl<K: Resource + Clone + DeserializeOwned + Debug> Api<K> {
    /// Gets a given object's "slot" on the Kubernetes API, designed for "get-or-create" and "get-and-modify" patterns
    ///
    /// This is similar to [`HashMap::entry`], but the [`Entry`] must be [`OccupiedEntry::commit`]ed for changes to be persisted.
    ///
    /// # Usage
    ///
    /// ```rust,no_run
    /// # use std::collections::BTreeMap;
    /// # use k8s_openapi::api::core::v1::ConfigMap;
    /// # async fn wrapper() -> Result <(), Box<dyn std::error::Error>> {
    /// let kube = kube::Client::try_default().await?;
    /// let cms = kube::Api::<ConfigMap>::namespaced(kube, "default");
    /// cms
    ///     // Try to get `entry-example` if it exists
    ///     .entry("entry-example").await?
    ///     // Modify object if it already exists
    ///     .and_modify(|cm| {
    ///         cm.data
    ///             .get_or_insert_with(BTreeMap::default)
    ///             .insert("already-exists".to_string(), "true".to_string());
    ///     })
    ///     // Provide a default object if it does not exist
    ///     .or_insert(|| ConfigMap::default())
    ///     // Modify the object unconditionally now that we have provided a default value
    ///     .and_modify(|cm| {
    ///         cm.data
    ///             .get_or_insert_with(BTreeMap::default)
    ///             .insert("modified".to_string(), "true".to_string());
    ///     })
    ///     // Save changes
    ///     .commit(&kube::api::PostParams::default()).await?;
    /// # Ok(())
    /// # }
    /// ```
    pub async fn entry<'a>(&'a self, name: &'a str) -> Result<Entry<'a, K>> {
        Ok(match self.get_opt(name).await? {
            Some(object) => Entry::Occupied(OccupiedEntry {
                api: self,
                dirtiness: Dirtiness::Clean,
                name,
                object,
            }),
            None => Entry::Vacant(VacantEntry { api: self, name }),
        })
    }
}

#[derive(Debug)]
/// A view into a single object, with enough context to create or update it
///
/// See [`Api::entry`] for more information.
pub enum Entry<'a, K> {
    /// An object that either exists on the server, or has been created locally (and is awaiting synchronization)
    Occupied(OccupiedEntry<'a, K>),
    /// An object that does not exist
    Vacant(VacantEntry<'a, K>),
}

impl<'a, K> Entry<'a, K> {
    /// Borrow the object, if it exists (on the API, or queued for creation using [`Entry::or_insert`])
    pub fn get(&self) -> Option<&K> {
        match self {
            Entry::Occupied(entry) => Some(entry.get()),
            Entry::Vacant(_) => None,
        }
    }

    /// Borrow the object mutably, if it exists (on the API, or queued for creation using [`Entry::or_insert`])
    ///
    /// [`OccupiedEntry::commit`] must be called afterwards for any changes to be persisted.
    pub fn get_mut(&mut self) -> Option<&mut K> {
        match self {
            Entry::Occupied(entry) => Some(entry.get_mut()),
            Entry::Vacant(_) => None,
        }
    }

    /// Let `f` modify the object, if it exists (on the API, or queued for creation using [`Entry::or_insert`])
    ///
    /// [`OccupiedEntry::commit`] must be called afterwards for any changes to be persisted.
    pub fn and_modify(self, f: impl FnOnce(&mut K)) -> Self {
        match self {
            Entry::Occupied(entry) => Entry::Occupied(entry.and_modify(f)),
            entry @ Entry::Vacant(_) => entry,
        }
    }

    /// Create a new object if it does not already exist
    ///
    /// [`OccupiedEntry::commit`] must be called afterwards for the change to be persisted.
    pub fn or_insert(self, default: impl FnOnce() -> K) -> OccupiedEntry<'a, K>
    where
        K: Resource,
    {
        match self {
            Entry::Occupied(entry) => entry,
            Entry::Vacant(entry) => entry.insert(default()),
        }
    }
}

/// A view into a single object that exists
///
/// The object may exist because it existed at the time of call to [`Api::entry`],
/// or because it was created by [`Entry::or_insert`].
#[derive(Debug)]
pub struct OccupiedEntry<'a, K> {
    api: &'a Api<K>,
    dirtiness: Dirtiness,
    name: &'a str,
    object: K,
}

#[derive(Debug)]
enum Dirtiness {
    /// The object has not been modified (locally) since the last API operation
    Clean,
    /// The object exists in the API, but has been modified locally
    Dirty,
    /// The object does not yet exist in the API, but was created locally
    New,
}

impl<'a, K> OccupiedEntry<'a, K> {
    /// Borrow the object
    pub fn get(&self) -> &K {
        &self.object
    }

    /// Borrow the object mutably
    ///
    /// [`OccupiedEntry::commit`] must be called afterwards for any changes to be persisted.
    pub fn get_mut(&mut self) -> &mut K {
        self.dirtiness = match self.dirtiness {
            Dirtiness::Clean => Dirtiness::Dirty,
            Dirtiness::Dirty => Dirtiness::Dirty,
            Dirtiness::New => Dirtiness::New,
        };
        &mut self.object
    }

    /// Let `f` modify the object
    ///
    /// [`OccupiedEntry::commit`] must be called afterwards for any changes to be persisted.
    pub fn and_modify(mut self, f: impl FnOnce(&mut K)) -> Self {
        f(self.get_mut());
        self
    }

    /// Take ownership over the object
    pub fn into_object(self) -> K {
        self.object
    }

    /// Save the object to the Kubernetes API, if any changes have been made
    ///
    /// The [`OccupiedEntry`] is updated with the new object (including changes made by the API server, such as
    /// `.metadata.resource_version`).
    ///
    /// # Errors
    ///
    /// This function can fail due to transient errors, or due to write conflicts (for example: if another client
    /// created the object between the calls to [`Api::entry`] and `OccupiedEntry::commit`, or because another
    /// client modified the object in the meantime).
    ///
    /// Any retries should be coarse-grained enough to also include the call to [`Api::entry`], so that the latest
    /// state can be fetched.
    #[tracing::instrument(skip(self))]
    pub async fn commit(&mut self, pp: &PostParams) -> Result<(), CommitError>
    where
        K: Resource + DeserializeOwned + Serialize + Clone + Debug,
    {
        self.prepare_for_commit()?;
        match self.dirtiness {
            Dirtiness::New => {
                self.object = self
                    .api
                    .create(pp, &self.object)
                    .await
                    .map_err(CommitError::Save)?
            }
            Dirtiness::Dirty => {
                self.object = self
                    .api
                    .replace(self.name, pp, &self.object)
                    .await
                    .map_err(CommitError::Save)?;
            }
            Dirtiness::Clean => (),
        };
        if !pp.dry_run {
            self.dirtiness = Dirtiness::Clean;
        }
        Ok(())
    }

    /// Validate that [`Self::object`] is valid, and refers to the same object as the original [`Api::entry`] call
    ///
    /// Defaults `ObjectMeta::name` and `ObjectMeta::namespace` if unset.
    fn prepare_for_commit(&mut self) -> Result<(), CommitValidationError>
    where
        K: Resource,
    {
        // Access `Self::object` directly rather than using `Self::get_mut` to avoid flagging the object as dirty
        let meta = self.object.meta_mut();
        match &mut meta.name {
            name @ None => *name = Some(self.name.to_string()),
            Some(name) if name != self.name => {
                return Err(CommitValidationError::NameMismatch {
                    object_name: name.clone(),
                    expected: self.name.to_string(),
                });
            }
            Some(_) => (),
        }
        match &mut meta.namespace {
            ns @ None => *ns = self.api.namespace.clone(),
            Some(ns) if Some(ns.as_str()) != self.api.namespace.as_deref() => {
                return Err(CommitValidationError::NamespaceMismatch {
                    object_namespace: Some(ns.clone()),
                    expected: self.api.namespace.clone(),
                });
            }
            Some(_) => (),
        }
        if let Some(generate_name) = &meta.generate_name {
            return Err(CommitValidationError::GenerateName {
                object_generate_name: generate_name.clone(),
            });
        }
        Ok(())
    }
}

#[derive(Debug, thiserror::Error)]
/// Commit errors
pub enum CommitError {
    /// Pre-commit validation failed
    #[error("failed to validate object for saving")]
    Validate(#[from] CommitValidationError),
    /// Failed to submit the new object to the Kubernetes API
    #[error("failed to save object")]
    Save(#[source] Error),
}

#[derive(Debug, thiserror::Error)]
/// Pre-commit validation errors
pub enum CommitValidationError {
    /// `ObjectMeta::name` does not match the name passed to [`Api::entry`]
    #[error(".metadata.name does not match the name passed to Api::entry (got: {object_name:?}, expected: {expected:?})")]
    NameMismatch {
        /// The name of the object (`ObjectMeta::name`)
        object_name: String,
        /// The name passed to [`Api::entry`]
        expected: String,
    },
    /// `ObjectMeta::namespace` does not match the namespace of the [`Api`]
    #[error(".metadata.namespace does not match the namespace of the Api (got: {object_namespace:?}, expected: {expected:?})")]
    NamespaceMismatch {
        /// The name of the object (`ObjectMeta::namespace`)
        object_namespace: Option<String>,
        /// The namespace of the [`Api`]
        expected: Option<String>,
    },
    /// `ObjectMeta::generate_name` must not be set
    #[error(".metadata.generate_name must not be set (got: {object_generate_name:?})")]
    GenerateName {
        /// The set name generation template of the object (`ObjectMeta::generate_name`)
        object_generate_name: String,
    },
}

/// A view of an object that does not yet exist
///
/// Created by [`Api::entry`], as a variant of [`Entry`]
#[derive(Debug)]
pub struct VacantEntry<'a, K> {
    api: &'a Api<K>,
    name: &'a str,
}

impl<'a, K> VacantEntry<'a, K> {
    /// Create a new object
    ///
    /// [`OccupiedEntry::commit`] must be called afterwards for the change to be persisted.
    #[tracing::instrument(skip(self, object))]
    pub fn insert(self, object: K) -> OccupiedEntry<'a, K>
    where
        K: Resource,
    {
        OccupiedEntry {
            api: self.api,
            dirtiness: Dirtiness::New,
            name: self.name,
            object,
        }
    }
}

#[cfg(test)]
mod tests {
    use std::collections::BTreeMap;

    use k8s_openapi::api::core::v1::ConfigMap;
    use kube_core::{
        params::{DeleteParams, PostParams},
        ErrorResponse, ObjectMeta,
    };

    use crate::{
        api::entry::{CommitError, Entry},
        Api, Client, Error,
    };

    #[tokio::test]
    #[ignore = "needs cluster (gets and writes cms)"]
    async fn entry_create_missing_object() -> Result<(), Box<dyn std::error::Error>> {
        let client = Client::try_default().await?;
        let api = Api::<ConfigMap>::default_namespaced(client);

        let object_name = "entry-missing-cm";
        if api.get_opt(object_name).await?.is_some() {
            api.delete(object_name, &DeleteParams::default()).await?;
        }

        let entry = api.entry(object_name).await?;
        let entry2 = api.entry(object_name).await?;
        assert_eq!(entry.get(), None);
        assert_eq!(entry2.get(), None);

        // Create object cleanly
        let mut entry = entry.or_insert(|| ConfigMap {
            data: Some([("key".to_string(), "value".to_string())].into()),
            ..ConfigMap::default()
        });
        entry.commit(&PostParams::default()).await?;
        assert_eq!(
            entry
                .get()
                .data
                .as_ref()
                .and_then(|data| data.get("key"))
                .map(String::as_str),
            Some("value")
        );
        let fetched_obj = api.get(object_name).await?;
        assert_eq!(
            fetched_obj
                .data
                .as_ref()
                .and_then(|data| data.get("key"))
                .map(String::as_str),
            Some("value")
        );

        // Update object
        entry
            .get_mut()
            .data
            .get_or_insert_with(BTreeMap::default)
            .insert("key".to_string(), "value2".to_string());
        entry.commit(&PostParams::default()).await?;
        assert_eq!(
            entry
                .get()
                .data
                .as_ref()
                .and_then(|data| data.get("key"))
                .map(String::as_str),
            Some("value2")
        );
        let fetched_obj = api.get(object_name).await?;
        assert_eq!(
            fetched_obj
                .data
                .as_ref()
                .and_then(|data| data.get("key"))
                .map(String::as_str),
            Some("value2")
        );

        // Object was already created in parallel, fail with a conflict error
        let mut entry2 = entry2.or_insert(|| ConfigMap {
            data: Some([("key".to_string(), "value3".to_string())].into()),
            ..ConfigMap::default()
        });
        assert!(
            matches!(dbg!(entry2.commit(&PostParams::default()).await), Err(CommitError::Save(Error::Api(ErrorResponse { reason, .. }))) if reason == "AlreadyExists")
        );

        // Cleanup
        api.delete(object_name, &DeleteParams::default()).await?;
        Ok(())
    }

    #[tokio::test]
    #[ignore = "needs cluster (gets and writes cms)"]
    async fn entry_update_existing_object() -> Result<(), Box<dyn std::error::Error>> {
        let client = Client::try_default().await?;
        let api = Api::<ConfigMap>::default_namespaced(client);

        let object_name = "entry-existing-cm";
        if api.get_opt(object_name).await?.is_some() {
            api.delete(object_name, &DeleteParams::default()).await?;
        }
        api.create(&PostParams::default(), &ConfigMap {
            metadata: ObjectMeta {
                namespace: api.namespace.clone(),
                name: Some(object_name.to_string()),
                ..ObjectMeta::default()
            },
            data: Some([("key".to_string(), "value".to_string())].into()),
            ..ConfigMap::default()
        })
        .await?;

        let mut entry = match api.entry(object_name).await? {
            Entry::Occupied(entry) => entry,
            entry => panic!("entry for existing object must be occupied: {entry:?}"),
        };
        let mut entry2 = match api.entry(object_name).await? {
            Entry::Occupied(entry) => entry,
            entry => panic!("entry for existing object must be occupied: {entry:?}"),
        };

        // Entry is up-to-date, modify cleanly
        entry
            .get_mut()
            .data
            .get_or_insert_with(BTreeMap::default)
            .insert("key".to_string(), "value2".to_string());
        entry.commit(&PostParams::default()).await?;
        assert_eq!(
            entry
                .get()
                .data
                .as_ref()
                .and_then(|data| data.get("key"))
                .map(String::as_str),
            Some("value2")
        );
        let fetched_obj = api.get(object_name).await?;
        assert_eq!(
            fetched_obj
                .data
                .as_ref()
                .and_then(|data| data.get("key"))
                .map(String::as_str),
            Some("value2")
        );

        // Object was already updated in parallel, fail with a conflict error
        entry2
            .get_mut()
            .data
            .get_or_insert_with(BTreeMap::default)
            .insert("key".to_string(), "value3".to_string());
        assert!(
            matches!(entry2.commit(&PostParams::default()).await, Err(CommitError::Save(Error::Api(ErrorResponse { reason, .. }))) if reason == "Conflict")
        );

        // Cleanup
        api.delete(object_name, &DeleteParams::default()).await?;
        Ok(())
    }

    #[tokio::test]
    #[ignore = "needs cluster (gets and writes cms)"]
    async fn entry_create_dry_run() -> Result<(), Box<dyn std::error::Error>> {
        let client = Client::try_default().await?;
        let api = Api::<ConfigMap>::default_namespaced(client);

        let object_name = "entry-cm-dry";
        if api.get_opt(object_name).await?.is_some() {
            api.delete(object_name, &DeleteParams::default()).await?;
        }

        let pp_dry = PostParams {
            dry_run: true,
            ..Default::default()
        };

        let entry = api.entry(object_name).await?;
        assert_eq!(entry.get(), None);

        // Create object dry-run
        let mut entry = entry.or_insert(|| ConfigMap {
            data: Some([("key".to_string(), "value".to_string())].into()),
            ..ConfigMap::default()
        });
        entry.commit(&pp_dry).await?;
        assert_eq!(
            entry
                .get()
                .data
                .as_ref()
                .and_then(|data| data.get("key"))
                .map(String::as_str),
            Some("value")
        );
        let fetched_obj = api.get_opt(object_name).await?;
        assert_eq!(fetched_obj, None);

        // Commit object creation properly
        entry.commit(&PostParams::default()).await?;
        assert_eq!(
            entry
                .get()
                .data
                .as_ref()
                .and_then(|data| data.get("key"))
                .map(String::as_str),
            Some("value")
        );
        let fetched_obj = api.get(object_name).await?;
        assert_eq!(
            fetched_obj
                .data
                .as_ref()
                .and_then(|data| data.get("key"))
                .map(String::as_str),
            Some("value")
        );

        // Update object dry-run
        entry
            .get_mut()
            .data
            .get_or_insert_with(BTreeMap::default)
            .insert("key".to_string(), "value2".to_string());
        entry.commit(&pp_dry).await?;
        assert_eq!(
            entry
                .get()
                .data
                .as_ref()
                .and_then(|data| data.get("key"))
                .map(String::as_str),
            Some("value2")
        );
        let fetched_obj = api.get(object_name).await?;
        assert_eq!(
            fetched_obj
                .data
                .as_ref()
                .and_then(|data| data.get("key"))
                .map(String::as_str),
            Some("value")
        );

        // Commit object update properly
        entry.commit(&PostParams::default()).await?;
        assert_eq!(
            entry
                .get()
                .data
                .as_ref()
                .and_then(|data| data.get("key"))
                .map(String::as_str),
            Some("value2")
        );
        let fetched_obj = api.get(object_name).await?;
        assert_eq!(
            fetched_obj
                .data
                .as_ref()
                .and_then(|data| data.get("key"))
                .map(String::as_str),
            Some("value2")
        );

        // Cleanup
        api.delete(object_name, &DeleteParams::default()).await?;
        Ok(())
    }
}