// Copyright (c) 2023-2026 ParadeDB, Inc.
//
// This file is part of ParadeDB - Postgres for Search and Analytics
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.

use crate::api::AsCStr;
use crate::postgres::customscan::joinscan::build::{ChildProjection, JoinCSClause};
use pgrx::pg_sys;
use pgrx::pg_sys::AsPgCStr;
use pgrx::PgList;
use serde::{Deserialize, Serialize};

pub const SCORE_COL_NAME: &str = "score";

/// Describes how a single output column of the JoinScan CustomScan is produced.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum OutputColumnInfo {
    /// A regular column backed by a Var in a source relation.
    Var {
        plan_position: usize,
        rti: pg_sys::Index,
        original_attno: i16,
    },
    /// A `paradedb.score()` call whose value comes from the DataFusion batch.
    Score {
        plan_position: usize,
        rti: pg_sys::Index,
    },
    /// A column pruned by a semi/anti join or a non-Var, non-score expression.
    /// Always emits NULL at execution time.
    Pruned,
}

impl From<&OutputColumnInfo> for ChildProjection {
    fn from(info: &OutputColumnInfo) -> Self {
        match info {
            OutputColumnInfo::Score { rti, .. } => ChildProjection::Score { rti: *rti },
            OutputColumnInfo::Var {
                rti,
                original_attno,
                ..
            } => ChildProjection::Column {
                rti: *rti,
                attno: *original_attno,
            },
            OutputColumnInfo::Pruned => ChildProjection::Column { rti: 0, attno: 0 },
        }
    }
}

/// Private data stored in the CustomPath/CustomScan for join operations.
#[derive(Debug, Clone, Serialize, Deserialize, Default)]
pub struct PrivateData {
    /// The join clause containing all information about both sides and the join itself.
    pub join_clause: JoinCSClause,
    /// Mapping of output column positions to their source relation and original attribute numbers.
    /// This is populated during planning (before setrefs) and used during execution.
    pub output_columns: Vec<OutputColumnInfo>,
    /// Serialized DataFusion LogicalPlan from planning phase.
    pub logical_plan: Option<bytes::Bytes>,
}

impl PrivateData {
    pub fn new(join_clause: JoinCSClause) -> Self {
        Self {
            join_clause,
            output_columns: Vec::new(),
            logical_plan: None,
        }
    }

    /// Returns a reference to the join clause.
    pub fn join_clause(&self) -> &JoinCSClause {
        &self.join_clause
    }

    /// Returns a mutable reference to the join clause.
    pub fn join_clause_mut(&mut self) -> &mut JoinCSClause {
        &mut self.join_clause
    }
}

impl From<*mut pg_sys::List> for PrivateData {
    fn from(list: *mut pg_sys::List) -> Self {
        unsafe {
            let list = PgList::<pg_sys::Node>::from_pg(list);
            let node = list.get_ptr(0).unwrap();
            let content = node
                .as_c_str()
                .unwrap()
                .to_str()
                .expect("string node should be valid utf8");
            serde_json::from_str(content).unwrap()
        }
    }
}

impl From<PrivateData> for *mut pg_sys::List {
    fn from(value: PrivateData) -> Self {
        let content = serde_json::to_string(&value).unwrap();
        unsafe {
            let mut ser = PgList::new();
            ser.push(pg_sys::makeString(content.as_pg_cstr()).cast::<pg_sys::Node>());
            ser.into_pg()
        }
    }
}