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// Copyright Materialize, Inc. and contributors. All rights reserved.
//
// Use of this software is governed by the Business Source License
// included in the LICENSE file.
//
// As of the Change Date specified in that file, in accordance with
// the Business Source License, use of this software will be governed
// by the Apache License, Version 2.0.

use std::fmt;
use std::str::FromStr;

use anyhow::{anyhow, Error};
use columnation::{Columnation, CopyRegion};
use mz_lowertest::MzReflect;
use mz_ore::id_gen::AtomicIdGen;
use mz_proto::{RustType, TryFromProtoError};
use proptest_derive::Arbitrary;
use serde::{Deserialize, Serialize};

use crate::CatalogItemId;

include!(concat!(env!("OUT_DIR"), "/mz_repr.global_id.rs"));

/// The identifier for an item/object.
///
/// WARNING: `GlobalId`'s `Ord` implementation has at various times expressed:
/// - Dependency ordering (items with greater `GlobalId`s can depend on those
/// lesser but never the other way around)
/// - Nothing at all regarding dependencies
///
/// Currently, `GlobalId`s express a dependency ordering. We hope to keep it
/// that way.
///
/// Before breaking this invariant, you should strongly consider alternative
/// designs, i.e. it is an intense "smell" if you need to allow inverted
/// `GlobalId` dependencies. Most likely, at some point in the future, you will
/// need to invert the dependency structure again and will regret having broken
/// it in the first place.
#[derive(
    Arbitrary,
    Clone,
    Copy,
    Debug,
    Eq,
    PartialEq,
    Ord,
    PartialOrd,
    Hash,
    Serialize,
    Deserialize,
    MzReflect,
)]
pub enum GlobalId {
    /// System namespace.
    System(u64),
    /// User namespace.
    User(u64),
    /// Transient namespace.
    Transient(u64),
    /// Dummy id for query being explained
    Explain,
}

impl GlobalId {
    /// Reports whether this ID is in the system namespace.
    pub fn is_system(&self) -> bool {
        matches!(self, GlobalId::System(_))
    }

    /// Reports whether this ID is in the user namespace.
    pub fn is_user(&self) -> bool {
        matches!(self, GlobalId::User(_))
    }

    /// Reports whether this ID is in the transient namespace.
    pub fn is_transient(&self) -> bool {
        matches!(self, GlobalId::Transient(_))
    }
}

impl FromStr for GlobalId {
    type Err = Error;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if s.len() < 2 {
            return Err(anyhow!("couldn't parse id {}", s));
        }
        if s == "Explained Query" {
            return Ok(GlobalId::Explain);
        }
        let val: u64 = s[1..].parse()?;
        match s.chars().next().unwrap() {
            's' => Ok(GlobalId::System(val)),
            'u' => Ok(GlobalId::User(val)),
            't' => Ok(GlobalId::Transient(val)),
            _ => Err(anyhow!("couldn't parse id {}", s)),
        }
    }
}

impl fmt::Display for GlobalId {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            GlobalId::System(id) => write!(f, "s{}", id),
            GlobalId::User(id) => write!(f, "u{}", id),
            GlobalId::Transient(id) => write!(f, "t{}", id),
            GlobalId::Explain => write!(f, "Explained Query"),
        }
    }
}

impl RustType<ProtoGlobalId> for GlobalId {
    fn into_proto(&self) -> ProtoGlobalId {
        use proto_global_id::Kind::*;
        ProtoGlobalId {
            kind: Some(match self {
                GlobalId::System(x) => System(*x),
                GlobalId::User(x) => User(*x),
                GlobalId::Transient(x) => Transient(*x),
                GlobalId::Explain => Explain(()),
            }),
        }
    }

    fn from_proto(proto: ProtoGlobalId) -> Result<Self, TryFromProtoError> {
        use proto_global_id::Kind::*;
        match proto.kind {
            Some(System(x)) => Ok(GlobalId::System(x)),
            Some(User(x)) => Ok(GlobalId::User(x)),
            Some(Transient(x)) => Ok(GlobalId::Transient(x)),
            Some(Explain(_)) => Ok(GlobalId::Explain),
            None => Err(TryFromProtoError::missing_field("ProtoGlobalId::kind")),
        }
    }
}

impl Columnation for GlobalId {
    type InnerRegion = CopyRegion<GlobalId>;
}

#[derive(Debug)]
pub struct TransientIdGen(AtomicIdGen);

impl TransientIdGen {
    pub fn new() -> Self {
        let inner = AtomicIdGen::default();
        // Transient IDs start at 1, so throw away the 0 value.
        let _ = inner.allocate_id();
        Self(inner)
    }

    pub fn allocate_id(&self) -> (CatalogItemId, GlobalId) {
        let inner = self.0.allocate_id();
        (CatalogItemId::Transient(inner), GlobalId::Transient(inner))
    }
}