// Copyright (c) 2026 Charles KWON OhJun (charleskwonohjun@gmail.com)
// All rights reserved.

// sqlglobals.go — Process-wide FiveSql2 counters that genuinely need
// cross-connection visibility, exposed to PRG via HB_FUNCs that wrap
// atomic / mutex primitives on the Go side. The PRG STATICs they
// replace (s_nSchemaVer, s_nRCJSeq, s_hAutoInc in TSqlExecutor.prg)
// were Go package vars under gengo; multi-pgserver-connection use
// raced on them and produced wrong cache invalidation, duplicate
// temp aliases, and "concurrent map writes" panics on the AUTOINC
// map's lazy first-init path.
//
// Wrapping these in Go-level synchronization is cheaper than the
// alternative (move to TSqlSession + thread oSession through every
// DDL caller in TSqlDDL.prg + IDENTITY handler in TSqlExecutor.prg)
// AND gives the right semantic — a CREATE TABLE on connection A
// MUST invalidate connection B's plan cache, an IDENTITY column
// MUST hand out monotonic values across all writers.

package hbrtl

import (
	"strings"
	"sync"
	"sync/atomic"

	"five/hbrt"
)

// --- Schema version counter ---
//
// Every DDL statement (CREATE / ALTER / DROP TABLE / INDEX / VIEW)
// calls SQL_BUMP_SCHEMA_VER. Plan-cache + DML-pcode-cache keys embed
// the current value as a prefix, so a bump invalidates every cached
// entry across every connection in one atomic write.
var sqlSchemaVer uint64

// --- RCJ sequence counter ---
//
// Recursive Common Join helper temp-alias counter. Each
// `RCJ_NNN` alias needs cross-connection uniqueness because two
// concurrent queries materialising different CTEs would otherwise
// collide on RCJ_1. Mod 100000 to keep aliases short.
var sqlRCJSeq uint64

// --- IDENTITY column registry ---
//
// Maps tableName (upper) → list of IDENTITY field names (upper).
// Populated by CREATE TABLE; read by INSERT to compute next value.
// Genuinely process-global: two connections inserting into the
// same table must see the same IDENTITY-field set.
var (
	sqlAutoIncMu sync.RWMutex
	sqlAutoInc   = map[string][]string{}
)

func init() {
	hbrt.HB_FUNC("SQLSCHEMAVER", hbSqlSchemaVer)
	hbrt.HB_FUNC("SQLBUMPSCHEMAVER", hbSqlBumpSchemaVer)
	hbrt.HB_FUNC("SQLNEXTRCJSEQ", hbSqlNextRCJSeq)
	hbrt.HB_FUNC("SQLSETAUTOINC", hbSqlSetAutoInc)
	hbrt.HB_FUNC("SQLGETAUTOINCFIELDS", hbSqlGetAutoIncFields)
}

func hbSqlSchemaVer(ctx *hbrt.HBContext) {
	ctx.RetNI(int(atomic.LoadUint64(&sqlSchemaVer)))
}

func hbSqlBumpSchemaVer(ctx *hbrt.HBContext) {
	ctx.RetNI(int(atomic.AddUint64(&sqlSchemaVer, 1)))
}

// hbSqlNextRCJSeq returns the next (atomic) RCJ sequence value
// modulo 100000, matching the previous PRG `s_nRCJSeq := (s_nRCJSeq + 1) % 100000`
// behaviour. Atomic increment first, then mod for the user-facing value.
func hbSqlNextRCJSeq(ctx *hbrt.HBContext) {
	n := atomic.AddUint64(&sqlRCJSeq, 1)
	ctx.RetNI(int(n % 100000))
}

// hbSqlSetAutoInc registers a field as IDENTITY for a table.
// Replaces TSqlExecutor.prg's SqlSetAutoInc which lazily init'd
// a STATIC hash → "concurrent map writes" panic under two
// concurrent CREATE TABLE calls.
func hbSqlSetAutoInc(ctx *hbrt.HBContext) {
	if ctx.PCount() < 2 || !ctx.IsChar(1) || !ctx.IsChar(2) {
		ctx.RetNil()
		return
	}
	key := strings.ToUpper(ctx.ParC(1))
	field := strings.ToUpper(ctx.ParC(2))
	sqlAutoIncMu.Lock()
	defer sqlAutoIncMu.Unlock()
	sqlAutoInc[key] = append(sqlAutoInc[key], field)
	ctx.RetNil()
}

// hbSqlGetAutoIncFields returns the list of IDENTITY field names
// for a table, or an empty array if none. PRG signature returns
// an Array of strings.
func hbSqlGetAutoIncFields(ctx *hbrt.HBContext) {
	if ctx.PCount() < 1 || !ctx.IsChar(1) {
		arr := hbrt.MakeArrayFrom(nil)
		ctx.RetVal(arr)
		return
	}
	key := strings.ToUpper(ctx.ParC(1))
	sqlAutoIncMu.RLock()
	fields := sqlAutoInc[key]
	sqlAutoIncMu.RUnlock()
	items := make([]hbrt.Value, len(fields))
	for i, f := range fields {
		items[i] = hbrt.MakeString(f)
	}
	ctx.RetVal(hbrt.MakeArrayFrom(items))
}