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

package pgserver

import (
	"fmt"
	"strconv"
	"time"

	"five/hbrt"
)

// PostgreSQL OID constants for the types FiveSql2 surfaces. Values
// match the canonical pg_type entries — psql and most drivers key
// their decoders off these.
const (
	oidBool        = 16
	oidInt4        = 23
	oidInt8        = 20
	oidNumeric     = 1700
	oidText        = 25
	oidDate        = 1082
	oidTimestamp   = 1114
)

// pgTypeFor returns (OID, declared-size). The declared size is -1
// for variable-width types (per PG convention). Sample is one
// representative value from the column; NIL falls back to TEXT
// because we don't have schema info at this layer.
func pgTypeFor(sample hbrt.Value) (oid uint32, size int16) {
	switch {
	case sample.IsLogical():
		return oidBool, 1
	case sample.IsNumeric():
		// Distinguish integer-ish from decimal so int columns
		// transit as INT4/INT8 (faster, BI tools render nicely).
		if isIntegerNumeric(sample) {
			n := sample.AsNumInt()
			if n >= -2147483648 && n <= 2147483647 {
				return oidInt4, 4
			}
			return oidInt8, 8
		}
		return oidNumeric, -1
	case sample.IsDate():
		return oidDate, 4
	case sample.IsTimestamp():
		return oidTimestamp, 8
	case sample.IsString():
		return oidText, -1
	default:
		// NIL or unknown — claim TEXT so the client decodes
		// whatever we send as a string. Real schema-aware OID
		// dispatch lands with extended-protocol Describe support
		// in v1.1.
		return oidText, -1
	}
}

// isIntegerNumeric distinguishes a whole-number Numeric from one
// that's been declared with decimals. Five's hbrt.Value carries
// the length/dec hints separately for printf-style formatting; if
// `dec` is 0, the source field declared no decimal places.
func isIntegerNumeric(v hbrt.Value) bool {
	// Fast path: tag-level integer subtype.
	if v.IsInt() || v.IsLong() {
		return true
	}
	// AsNumDouble rounding check — within 1e-9 of an integer, no
	// declared decimal places.
	d := v.AsNumDouble()
	if d != float64(int64(d)) {
		return false
	}
	return v.Decimal() == 0
}

// encodeText writes one cell as a text-format PG byte slice. NULL
// is signalled by returning nil (DataRow distinguishes nil from
// empty []byte and sends length=-1 vs length=0 accordingly).
func encodeText(v hbrt.Value) []byte {
	if v.IsNil() {
		return nil
	}
	switch {
	case v.IsLogical():
		if v.AsBool() {
			return []byte{'t'}
		}
		return []byte{'f'}
	case v.IsNumeric():
		if isIntegerNumeric(v) {
			return []byte(strconv.FormatInt(v.AsNumInt(), 10))
		}
		precision := int(v.Decimal())
		if precision <= 0 || precision > 30 {
			precision = 10
		}
		return []byte(strconv.FormatFloat(v.AsNumDouble(), 'f', precision, 64))
	case v.IsDate():
		y, m, d := julianToYMD(v.AsJulian())
		return []byte(fmt.Sprintf("%04d-%02d-%02d", y, m, d))
	case v.IsTimestamp():
		// Convert Julian + ms to a Go time and format.
		jul := v.AsJulian()
		y, mo, d := julianToYMD(jul)
		ms := v.AsTimeMs()
		hh := ms / 3600000
		ms -= hh * 3600000
		mm := ms / 60000
		ms -= mm * 60000
		ss := ms / 1000
		ms -= ss * 1000
		return []byte(fmt.Sprintf("%04d-%02d-%02d %02d:%02d:%02d.%03d", y, mo, d, hh, mm, ss, ms))
	case v.IsString():
		return []byte(v.AsString())
	default:
		// Fallback: best-effort string conversion.
		return []byte(fmt.Sprintf("%v", v))
	}
}

// julianToYMD converts an integer Julian day number to (year, month,
// day). Matches Harbour's hb_dateDecode algorithm used elsewhere in
// the runtime; duplicated here to avoid pulling in hbrtl which
// would create an import cycle.
func julianToYMD(j int64) (year, month, day int) {
	if j <= 0 {
		return 0, 0, 0
	}
	a := j + 32044
	b := (4*a + 3) / 146097
	c := a - (b*146097)/4
	d := (4*c + 3) / 1461
	e := c - (1461*d)/4
	m := (5*e + 2) / 153
	day = int(e - (153*m+2)/5 + 1)
	month = int(m + 3 - 12*(m/10))
	year = int(b*100 + d - 4800 + (m / 10))
	return
}

// Force time package import — we'll need it for Timestamp parsing
// when extended protocol lands. Stub function keeps the import
// from being pruned in v1.0-skeleton.
var _ = time.Date