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

// FiveSql2 scalar helpers — Go replacements for the PRG functions in
// _FiveSql2/src/TSqlFunc.prg. These are invoked per-operator during
// expression evaluation (WHERE / HAVING / CASE); porting removes PRG
// VM frame overhead on the hot interpreter path. Semantics match the
// PRG source byte-for-byte.

package hbrtl

import (
	"fmt"
	"math"
	"strconv"
	"strings"

	"five/hbrt"
)

// FiveSql2 lexer token type codes — must match FiveSqlDef.ch.
const (
	tkEnd    = 0
	tkName   = 1
	tkText   = 2
	tkNum    = 3
	tkComma  = 4
	tkDot    = 5
	tkStar   = 6
	tkLPar   = 7
	tkRPar   = 8
	tkEq     = 9
	tkNEq    = 10
	tkLT     = 11
	tkGT     = 12
	tkLTE    = 13
	tkGTE    = 14
	tkQMark  = 15
	tkPlus   = 16
	tkMinus  = 17
	tkSlash  = 18
	tkPipes  = 19
)

// makeTokValue wraps a (type, text) pair into the 2-element PRG array
// that TSqlParser2 consumes: { nTokenType, cTokenValue }.
func makeTokValue(ttype int, text string) hbrt.Value {
	return hbrt.MakeArrayFrom([]hbrt.Value{
		hbrt.MakeNumInt(int64(ttype)),
		hbrt.MakeString(text),
	})
}

// lexSQL is the Go port of TSqlLexer:Tokenize — byte-level FSM over the
// ASCII input string. Produces the same aTokens shape the PRG lexer did.
func lexSQL(s string) []hbrt.Value {
	toks := make([]hbrt.Value, 0, 32)
	n := len(s)
	i := 0
	for i < n {
		c := s[i]

		// Whitespace
		if c == ' ' || c == '\t' || c == '\n' || c == '\r' {
			i++
			continue
		}

		// Line comment `-- ...`
		if c == '-' && i+1 < n && s[i+1] == '-' {
			i += 2
			for i < n && s[i] != '\n' {
				i++
			}
			continue
		}

		// Block comment `/* ... */`
		if c == '/' && i+1 < n && s[i+1] == '*' {
			i += 2
			for i < n-1 {
				if s[i] == '*' && s[i+1] == '/' {
					i += 2
					break
				}
				i++
			}
			continue
		}

		// String literal (single-quoted, '' escapes a quote)
		if c == '\'' {
			i++
			start := i
			var sb strings.Builder
			inEscape := false
			for i < n {
				cc := s[i]
				if cc == '\'' {
					if i+1 < n && s[i+1] == '\'' {
						if !inEscape {
							sb.WriteString(s[start:i])
							inEscape = true
						} else {
							sb.WriteByte('\'')
							sb.WriteString(s[start:i])
						}
						sb.WriteByte('\'')
						i += 2
						start = i
					} else {
						break
					}
				} else {
					i++
				}
			}
			var val string
			if inEscape {
				sb.WriteString(s[start:i])
				val = sb.String()
			} else {
				val = s[start:i]
			}
			if i < n {
				i++ // skip closing quote
			}
			toks = append(toks, makeTokValue(tkText, val))
			continue
		}

		// Numeric literal
		if c >= '0' && c <= '9' {
			start := i
			for i < n && ((s[i] >= '0' && s[i] <= '9') || s[i] == '.') {
				i++
			}
			toks = append(toks, makeTokValue(tkNum, s[start:i]))
			continue
		}

		// Identifier / keyword
		if isAlphaSQL(c) || c == '_' {
			start := i
			for i < n && (isAlphaSQL(s[i]) || (s[i] >= '0' && s[i] <= '9') || s[i] == '_') {
				i++
			}
			toks = append(toks, makeTokValue(tkName, strings.ToUpper(s[start:i])))
			continue
		}

		// Bracketed identifier `[col name]`
		if c == '[' {
			i++
			start := i
			for i < n && s[i] != ']' {
				i++
			}
			name := strings.ToUpper(s[start:i])
			if i < n {
				i++ // skip ']'
			}
			toks = append(toks, makeTokValue(tkName, name))
			continue
		}

		// Parameter placeholder
		if c == '?' {
			toks = append(toks, makeTokValue(tkQMark, "?"))
			i++
			continue
		}

		// Multi-char + single-char operators / punctuation
		switch c {
		case ',':
			toks = append(toks, makeTokValue(tkComma, ","))
			i++
		case '.':
			// Harbour logical literals inside SQL text: `.T.` / `.F.` /
			// `.Y.` / `.N.`. Emit TK_NAME("TRUE"/"FALSE") so the
			// parser's primary handles them alongside SQL TRUE/FALSE
			// keywords without a dedicated token kind. Must precede
			// the bare `.` → TK_DOT emission below, otherwise the
			// three chars tokenize as DOT + NAME("T") + DOT and the
			// INSERT column alignment drifts by two.
			if i+2 < n && s[i+2] == '.' {
				lit := s[i+1]
				if lit == 't' || lit == 'T' || lit == 'y' || lit == 'Y' {
					toks = append(toks, makeTokValue(tkName, "TRUE"))
					i += 3
					continue
				}
				if lit == 'f' || lit == 'F' || lit == 'n' || lit == 'N' {
					toks = append(toks, makeTokValue(tkName, "FALSE"))
					i += 3
					continue
				}
			}
			toks = append(toks, makeTokValue(tkDot, "."))
			i++
		case '*':
			toks = append(toks, makeTokValue(tkStar, "*"))
			i++
		case '(':
			toks = append(toks, makeTokValue(tkLPar, "("))
			i++
		case ')':
			toks = append(toks, makeTokValue(tkRPar, ")"))
			i++
		case '+':
			toks = append(toks, makeTokValue(tkPlus, "+"))
			i++
		case '-':
			toks = append(toks, makeTokValue(tkMinus, "-"))
			i++
		case '/':
			toks = append(toks, makeTokValue(tkSlash, "/"))
			i++
		case '|':
			if i+1 < n && s[i+1] == '|' {
				toks = append(toks, makeTokValue(tkPipes, "||"))
				i += 2
			} else {
				i++
			}
		case '=':
			toks = append(toks, makeTokValue(tkEq, "="))
			i++
		case '<':
			if i+1 < n && s[i+1] == '=' {
				toks = append(toks, makeTokValue(tkLTE, "<="))
				i += 2
			} else if i+1 < n && s[i+1] == '>' {
				toks = append(toks, makeTokValue(tkNEq, "<>"))
				i += 2
			} else {
				toks = append(toks, makeTokValue(tkLT, "<"))
				i++
			}
		case '>':
			if i+1 < n && s[i+1] == '=' {
				toks = append(toks, makeTokValue(tkGTE, ">="))
				i += 2
			} else {
				toks = append(toks, makeTokValue(tkGT, ">"))
				i++
			}
		case '!':
			if i+1 < n && s[i+1] == '=' {
				toks = append(toks, makeTokValue(tkNEq, "!="))
				i += 2
			} else {
				i++
			}
		case ';':
			i++
		default:
			i++
		}
	}

	toks = append(toks, makeTokValue(tkEnd, ""))
	return toks
}

func isAlphaSQL(c byte) bool {
	return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z')
}

// SqlLexerTokenize(cSQL) → aTokens
// Direct Go port of TSqlLexer:Tokenize. Returns the same
// { { nType, cText }, ... } structure the PRG version produced.
func SqlLexerTokenize(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	toks := lexSQL(t.Local(1).AsString())
	t.PushValue(hbrt.MakeArrayFrom(toks))
	t.RetValue()
}

// SqlLexAndExtractTemplate(cSQL) → { aTokens, cKey, aParams }
//
// Combined lex + template extraction — one Go call replaces three
// PRG-to-Go boundary crossings (lex, get tokens, extract). aTokens
// already has literal tokens replaced with TK_QMARK; aParams holds
// the extracted literal values in positional order; cKey is the
// plan cache key (digest of the normalized token-type sequence).
func SqlLexAndExtractTemplate(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()

	src := t.Local(1).AsString()
	toks := lexSQL(src)

	params := make([]hbrt.Value, 0, 8)
	var keyBuf strings.Builder
	keyBuf.Grow(len(src))

	for _, tv := range toks {
		tok := tv.AsArray()
		if tok == nil || len(tok.Items) < 2 {
			continue
		}
		ttype := int(tok.Items[0].AsNumInt())
		switch ttype {
		case tkText:
			params = append(params, tok.Items[1])
			tok.Items[0] = hbrt.MakeNumInt(tkQMark)
			tok.Items[1] = hbrt.MakeString("?")
			keyBuf.WriteByte('?')
		case tkNum:
			s := tok.Items[1].AsString()
			var val hbrt.Value
			if i, err := strconv.ParseInt(s, 10, 64); err == nil {
				val = hbrt.MakeNumInt(i)
			} else if f, err := strconv.ParseFloat(s, 64); err == nil {
				val = hbrt.MakeDoubleAuto(f)
			} else {
				val = hbrt.MakeString(s)
			}
			params = append(params, val)
			tok.Items[0] = hbrt.MakeNumInt(tkQMark)
			tok.Items[1] = hbrt.MakeString("?")
			keyBuf.WriteByte('#')
		default:
			keyBuf.WriteByte(byte(ttype) + 0x20)
			if ttype == tkName {
				keyBuf.WriteString(tok.Items[1].AsString())
				keyBuf.WriteByte(' ')
			}
		}
	}

	result := hbrt.MakeArrayFrom([]hbrt.Value{
		hbrt.MakeArrayFrom(toks),
		hbrt.MakeString(keyBuf.String()),
		hbrt.MakeArrayFrom(params),
	})
	t.PushValue(result)
	t.RetValue()
}

// SqlExtractTemplate(aTokens) → { cKey, aParams }
//
// Walks a FiveSql2 lexer token stream, replacing string (TK_TEXT=2)
// and numeric (TK_NUM=3) literals with the parameter placeholder
// token (TK_QMARK=15). Collected literal values are returned as
// aParams in their natural left-to-right order.
//
// Each token is a 2-element array {nTokenType, cTokenValue}. The
// mutation is in place so the caller can pass the resulting aTokens
// straight into TSqlParser2 — the parser then emits ND_PAR nodes
// that resolve against aParams at execution time.
//
// The template key is a compact digest of the non-literal token
// type sequence, used as the plan cache key for queries that share
// the same shape but differ only in literal values. Queries like:
//
//    INSERT INTO t VALUES (1,'a')
//    INSERT INTO t VALUES (2,'b')
//
// produce the SAME key once literals are collapsed to '?', letting
// the plan cache hit from the 2nd call onward.
//
// Returns a 2-element array: { cKey, aParams }.
func SqlExtractTemplate(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()

	tokensVal := t.Local(1)
	if !tokensVal.IsArray() {
		empty := hbrt.MakeArrayFrom([]hbrt.Value{
			hbrt.MakeString(""),
			hbrt.MakeArrayFrom(nil),
		})
		t.PushValue(empty)
		t.RetValue()
		return
	}

	toks := tokensVal.AsArray().Items
	params := make([]hbrt.Value, 0, 8)

	// Template key — cheap digest of the token-type sequence.
	var keyBuf strings.Builder
	keyBuf.Grow(len(toks) * 2)

	const (
		tkText  = 2
		tkNum   = 3
		tkQmark = 15
	)

	for _, tokVal := range toks {
		tok := tokVal.AsArray()
		if tok == nil || len(tok.Items) < 2 {
			continue
		}
		ttype := int(tok.Items[0].AsNumInt())

		switch ttype {
		case tkText:
			// String literal → TK_QMARK + save raw string value.
			params = append(params, tok.Items[1])
			tok.Items[0] = hbrt.MakeInt(tkQmark)
			tok.Items[1] = hbrt.MakeString("?")
			keyBuf.WriteByte('?')
		case tkNum:
			// Numeric literal → TK_QMARK + parse value. Integer form
			// when possible (common for id columns), double otherwise.
			s := tok.Items[1].AsString()
			var val hbrt.Value
			if i, err := strconv.ParseInt(s, 10, 64); err == nil {
				val = hbrt.MakeNumInt(i)
			} else if f, err := strconv.ParseFloat(s, 64); err == nil {
				val = hbrt.MakeDoubleAuto(f)
			} else {
				val = hbrt.MakeString(s)
			}
			params = append(params, val)
			tok.Items[0] = hbrt.MakeInt(tkQmark)
			tok.Items[1] = hbrt.MakeString("?")
			keyBuf.WriteByte('#')
		default:
			// Non-literal token — include type code + text so two
			// different-but-same-shape queries distinguish properly
			// (e.g., SELECT id vs SELECT name).
			keyBuf.WriteByte(byte(ttype) + 0x20) // offset to printable
			if ttype == 1 {                       // TK_NAME — include name text
				keyBuf.WriteString(strings.ToUpper(tok.Items[1].AsString()))
				keyBuf.WriteByte(' ')
			}
		}
	}

	result := hbrt.MakeArrayFrom([]hbrt.Value{
		hbrt.MakeString(keyBuf.String()),
		hbrt.MakeArrayFrom(params),
	})
	t.PushValue(result)
	t.RetValue()
}

// SqlCoerceStr(x) → cString
// Converts any scalar to its canonical string form (NULL-safe).
func SqlCoerceStr(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	v := t.Local(1)
	t.RetString(sqlCoerceStr(v))
}

func sqlCoerceStr(v hbrt.Value) string {
	switch {
	case v.IsNil():
		return ""
	case v.IsString():
		return v.AsString()
	case v.IsNumeric():
		if v.IsNumInt() {
			return strconv.FormatInt(v.AsNumInt(), 10)
		}
		return strconv.FormatFloat(v.AsNumDouble(), 'g', -1, 64)
	case v.IsLogical():
		if v.AsBool() {
			return "T"
		}
		return "F"
	case v.IsDate():
		// Date → "YYYYMMDD" (the DToS canonical form). Previously
		// dates fell through to the empty-string default, so any
		// `WHERE date_col = '20240115'` comparison silently
		// compared "" to the literal and returned 0 rows. YYYYMMDD
		// is format-independent and matches how Harbour's DToS /
		// HbSToD pair encodes dates for byte-stable round-trip.
		y, m, d := julianToDate(v.AsJulian())
		return fmt.Sprintf("%04d%02d%02d", y, m, d)
	case v.IsTimestamp():
		y, m, d := julianToDate(v.AsJulian())
		ms := v.AsTimeMs()
		hh := ms / 3600000
		mm := (ms % 3600000) / 60000
		ss := (ms % 60000) / 1000
		return fmt.Sprintf("%04d%02d%02d%02d%02d%02d", y, m, d, hh, mm, ss)
	}
	return ""
}

// SqlCoerceNum(x) → nNumber
// Converts any scalar to numeric (NULL → 0, bool → 1/0, string → Val).
func SqlCoerceNum(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	v := t.Local(1)
	switch {
	case v.IsNil():
		t.RetInt(0)
	case v.IsNumeric():
		t.RetVal(v)
	case v.IsString():
		t.RetVal(hbrt.MakeDoubleAuto(parseLeadingNumeric(v.AsString())))
	case v.IsLogical():
		if v.AsBool() {
			t.RetInt(1)
		} else {
			t.RetInt(0)
		}
	default:
		t.RetInt(0)
	}
}

// SqlCoerceForCmp(x) → xNormalized
// Trim + upper-case strings; pass-through for other types. Used to
// make SQL equality/ordering case-insensitive on CHAR values.
func SqlCoerceForCmp(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	v := t.Local(1)
	if v.IsString() {
		t.RetString(strings.ToUpper(strings.TrimSpace(v.AsString())))
		return
	}
	t.RetVal(v)
}

// SqlIsTrue(x) → lBool
// SQL truthiness: NIL → false, empty string → false, 0 → false.
func SqlIsTrue(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	t.RetBool(sqlIsTrue(t.Local(1)))
}

func sqlIsTrue(v hbrt.Value) bool {
	switch {
	case v.IsNil():
		return false
	case v.IsLogical():
		return v.AsBool()
	case v.IsNumeric():
		if v.IsNumInt() {
			return v.AsNumInt() != 0
		}
		return v.AsNumDouble() != 0 && !math.IsNaN(v.AsNumDouble())
	case v.IsString():
		return strings.TrimSpace(v.AsString()) != ""
	}
	return false
}

// SqlCmpEq(a, b) → lBool
// Case-insensitive equality with cross-type N↔C coercion.
func SqlCmpEq(t *hbrt.Thread) {
	t.Frame(2, 0)
	defer t.EndProc()
	t.RetBool(sqlCmpEq(t.Local(1), t.Local(2)))
}

func sqlCmpEq(a, b hbrt.Value) bool {
	aNil, bNil := a.IsNil(), b.IsNil()
	if aNil || bNil {
		return aNil && bNil
	}
	// Numeric: compare regardless of Int/Double distinction.
	if a.IsNumeric() && b.IsNumeric() {
		return a.AsNumDouble() == b.AsNumDouble()
	}
	if a.IsString() && b.IsString() {
		return strings.EqualFold(
			strings.TrimSpace(a.AsString()),
			strings.TrimSpace(b.AsString()),
		)
	}
	if a.IsLogical() && b.IsLogical() {
		return a.AsBool() == b.AsBool()
	}
	if a.IsDate() && b.IsDate() {
		return a.AsJulian() == b.AsJulian()
	}
	// Cross-type N / C coercion.
	if a.IsNumeric() && b.IsString() {
		return a.AsNumDouble() == parseLeadingNumeric(b.AsString())
	}
	if a.IsString() && b.IsNumeric() {
		return parseLeadingNumeric(a.AsString()) == b.AsNumDouble()
	}
	// Cross-type D / C coercion. SQL tests often write the right-hand
	// side as a literal "YYYYMMDD" string (the DToS canonical form);
	// without this arm the comparison fell through to false and
	// `WHERE hired = '20240115'` silently returned no rows.
	if a.IsDate() && b.IsString() {
		return sqlCmpDateStr(a, b)
	}
	if a.IsString() && b.IsDate() {
		return sqlCmpDateStr(b, a)
	}
	return false
}

// sqlCmpDateStr returns true when the date's YYYYMMDD form equals the
// string operand after trim + separator strip. Accepts both DToS form
// (20260425) and the more common ISO/SQL forms (2026-04-25, 2026/04/25,
// 2026.04.25). Without normalization, `WHERE d = '2026-04-25'` silently
// returned no rows because the literal didn't match the YYYYMMDD form.
func sqlCmpDateStr(d, s hbrt.Value) bool {
	y, m, day := julianToDate(d.AsJulian())
	return fmt.Sprintf("%04d%02d%02d", y, m, day) == normalizeDateStr(s.AsString())
}

// normalizeDateStr strips common date separators ('-', '/', '.') so
// '2026-04-25', '2026/04/25', '2026.04.25', '20260425' all collapse
// to '20260425'. Caller is responsible for ensuring the input is
// date-shaped; non-date strings are passed through with separators
// removed (harmless — a comparison against a date will still fail).
func normalizeDateStr(s string) string {
	s = strings.TrimSpace(s)
	if !strings.ContainsAny(s, "-/.") {
		return s
	}
	var b strings.Builder
	b.Grow(len(s))
	for i := 0; i < len(s); i++ {
		c := s[i]
		if c != '-' && c != '/' && c != '.' {
			b.WriteByte(c)
		}
	}
	return b.String()
}

// SqlCmpLt(a, b) → lBool
// Case-insensitive less-than with cross-type N↔C coercion.
func SqlCmpLt(t *hbrt.Thread) {
	t.Frame(2, 0)
	defer t.EndProc()
	t.RetBool(sqlCmpLt(t.Local(1), t.Local(2)))
}

func sqlCmpLt(a, b hbrt.Value) bool {
	if a.IsNil() || b.IsNil() {
		return false
	}
	if a.IsNumeric() && b.IsNumeric() {
		return a.AsNumDouble() < b.AsNumDouble()
	}
	if a.IsString() && b.IsString() {
		return strings.ToUpper(strings.TrimSpace(a.AsString())) <
			strings.ToUpper(strings.TrimSpace(b.AsString()))
	}
	if a.IsDate() && b.IsDate() {
		return a.AsJulian() < b.AsJulian()
	}
	if a.IsLogical() && b.IsLogical() {
		return !a.AsBool() && b.AsBool()
	}
	if a.IsNumeric() && b.IsString() {
		return a.AsNumDouble() < parseLeadingNumeric(b.AsString())
	}
	if a.IsString() && b.IsNumeric() {
		return parseLeadingNumeric(a.AsString()) < b.AsNumDouble()
	}
	// Cross-type D / C: compare DToS form lexicographically (YYYYMMDD
	// sorts identically to chronological order for well-formed strings).
	// Normalize the string operand so 'YYYY-MM-DD' / 'YYYY/MM/DD' /
	// 'YYYY.MM.DD' compare correctly, not just bare 'YYYYMMDD'. Without
	// this, `WHERE d > '2026-06-01'` collapsed to a string compare of
	// '20260425' < '2026-06-01' which is false because '2' < '2', '0' < '0'
	// proceeds until '4' vs '-' (45 vs 45 — actually '4' = 0x34, '-' = 0x2d)
	// → '4' > '-' so `'20260425' < '2026-06-01'` is false → all dates
	// returned as "less than" → all rows match. Confusing but the symptom
	// was every WHERE date > ISO-string returning the full table.
	if a.IsDate() && b.IsString() {
		y, m, d := julianToDate(a.AsJulian())
		return fmt.Sprintf("%04d%02d%02d", y, m, d) < normalizeDateStr(b.AsString())
	}
	if a.IsString() && b.IsDate() {
		y, m, d := julianToDate(b.AsJulian())
		return normalizeDateStr(a.AsString()) < fmt.Sprintf("%04d%02d%02d", y, m, d)
	}
	return false
}

// SqlIsAggName(cName) → lBool
// Go-native replacement for TSqlExpr.prg SqlIsAggName. The PRG version
// was `("," + c + ",") $ ("," + AGG_FUNCTIONS + ",")` — two string
// allocations + a substring scan per call. Profile showed this at
// 8.7% of B4 GROUP+HAVING CPU. Uses the aggFuncSet already declared
// in sqlexpr.go for SqlExprHasAgg.
func SqlIsAggName(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	name := t.Local(1).AsString()
	if name == "" {
		t.RetBool(false)
		return
	}
	// Upper-case without allocating unless needed.
	upper := name
	for i := 0; i < len(name); i++ {
		c := name[i]
		if c >= 'a' && c <= 'z' {
			upper = strings.ToUpper(name)
			break
		}
	}
	_, ok := aggFuncSet[upper]
	t.RetBool(ok)
}