package sql

import (
	"fmt"
	"regexp"
	"sort"
	"strings"

	"git.secnex.io/secnex/pgson/schema"
)

var (
	IdentifierRegex = regexp.MustCompile(`^[a-zA-Z_][a-zA-Z0-9_]*$`)
	TypeMap         = map[string]string{
		"string":   "VARCHAR",
		"int":      "INTEGER",
		"float":    "FLOAT",
		"bool":     "BOOLEAN",
		"date":     "DATE",
		"time":     "TIME",
		"datetime": "TIMESTAMP",
		"uuid":     "UUID",
		"json":     "JSONB",
		"hash":     "VARCHAR",
	}
	FkActions = map[string]struct{}{
		"CASCADE":     {},
		"RESTRICT":    {},
		"SET NULL":    {},
		"NO ACTION":   {},
		"SET DEFAULT": {},
	}
	DefaultFunctions = map[string]struct{}{
		"CURRENT_TIMESTAMP":  {},
		"now()":              {},
		"uuid_generate_v4()": {},
	}
	AlgorithmMap = map[string]struct{}{
		"argon2": {},
		"bcrypt": {},
		"md5":    {},
		"sha256": {},
		"sha512": {},
	}
)

func ValidateIdent(name string) error {
	if !IdentifierRegex.MatchString(name) {
		return fmt.Errorf("invalid identifier: %s", name)
	}
	return nil
}

func ValidateType(name string) (string, error) {
	pg, ok := TypeMap[name]
	if !ok {
		return "", fmt.Errorf("invalid type: %s", name)
	}
	return pg, nil
}

func ValidateAction(act string) (string, error) {
	a := strings.ToUpper(act)
	if _, ok := FkActions[a]; !ok {
		return "", fmt.Errorf("invalid action: %s", act)
	}
	return a, nil
}

func ValidateDefault(def string) (string, error) {
	if regexp.MustCompile(`^\d+(\.\d+)?$`).MatchString(def) || regexp.MustCompile(`^'.*'$`).MatchString(def) {
		return def, nil
	}
	if _, ok := DefaultFunctions[strings.ToLower(def)]; ok {
		return def, nil
	}
	return "", fmt.Errorf("invalid default: %s", def)
}

func ValidateReferences(refs *schema.Reference) error {
	if err := ValidateIdent(refs.Table); err != nil {
		return err
	}
	if err := ValidateIdent(refs.Column); err != nil {
		return err
	}
	return nil
}

func ValidateAlgorithm(algo string) error {
	a := strings.ToUpper(algo)
	if _, ok := AlgorithmMap[a]; !ok {
		return fmt.Errorf("invalid algorithm: %s", algo)
	}
	return nil
}

func ValidatePrimary(primary bool) error {
	if primary {
		return nil
	}
	return fmt.Errorf("primary is required")
}

func ValidateUnique(unique bool) error {
	if unique {
		return nil
	}
	return fmt.Errorf("unique is required")
}

func ValidateComment(comment *string) error {
	if comment == nil {
		return nil
	}
	return ValidateIdent(*comment)
}

func QuoteIdent(name string) string {
	return `"` + strings.ReplaceAll(name, `"`, `""`) + `"`
}

func QuoteLiteral(s string) string {
	s = strings.ReplaceAll(s, "\x00", "")

	var b strings.Builder
	b.Grow(len(s) + 2)
	b.WriteByte('\'')

	for _, r := range s {
		switch r {
		case '\'':
			b.WriteString("''")
		case '\\':
			b.WriteString("\\\\")
		case '\x00':
			continue
		case '\t', '\n', '\r':
			b.WriteRune(r)
		default:
			if r < 0x20 {
				b.WriteString(fmt.Sprintf("\\%03o", r))
			} else {
				b.WriteRune(r)
			}
		}
	}

	b.WriteByte('\'')
	return b.String()
}

func QuoteValue(v any) string {
	if v == nil {
		return "NULL"
	}

	switch val := v.(type) {
	case string:
		if matched, _ := regexp.MatchString(`^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$`, strings.ToLower(val)); matched {
			return QuoteLiteral(val)
		}
		return QuoteLiteral(val)
	case int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64:
		return fmt.Sprintf("%v", val)
	case float32, float64:
		return fmt.Sprintf("%v", val)
	case bool:
		if val {
			return "TRUE"
		}
		return "FALSE"
	default:
		return QuoteLiteral(fmt.Sprintf("%v", val))
	}
}

func BuildWhereClause(conditions map[string]any) (string, error) {
	if len(conditions) == 0 {
		return "", nil
	}

	var clauses []string
	keys := make([]string, 0, len(conditions))
	for k := range conditions {
		keys = append(keys, k)
	}
	sort.Strings(keys)

	for _, col := range keys {
		if err := ValidateIdent(col); err != nil {
			return "", fmt.Errorf("invalid column identifier in WHERE clause: %s", col)
		}
		value := conditions[col]
		if value == nil {
			clauses = append(clauses, fmt.Sprintf("%s IS NULL", QuoteIdent(col)))
		} else {
			clauses = append(clauses, fmt.Sprintf("%s = %s", QuoteIdent(col), QuoteValue(value)))
		}
	}

	return " WHERE " + strings.Join(clauses, " AND "), nil
}