package source

import (
	"fmt"
	"regexp"
	"strconv"
	"strings"
	"unicode"

	"golang.org/x/exp/slices"

	"github.com/neilotoole/sq/libsq/core/stringz"

	"github.com/neilotoole/sq/libsq/core/errz"
)

var (
	handlePattern = regexp.MustCompile(`\A@([a-zA-Z][a-zA-Z0-9_]*)(/[a-zA-Z][a-zA-Z0-9_]*)*$`)
	groupPattern  = regexp.MustCompile(`\A([a-zA-Z][a-zA-Z0-9_]*)(/[a-zA-Z][a-zA-Z0-9_]*)*$`)
	tablePattern  = regexp.MustCompile(`\A[a-zA-Z_][a-zA-Z0-9_]*$`)
)

// ValidHandle returns an error if handle is
// not an acceptable source handle value.
// Valid input must match:
//
//	\A@([a-zA-Z][a-zA-Z0-9_]*)(/[a-zA-Z][a-zA-Z0-9_]*)*$
//
// Examples:
//
//	@handle
//	@group/handle
//	@group/sub/sub2/handle
//
// See also: IsValidHandle.
func ValidHandle(handle string) error {
	const msg = `invalid source handle: %s`
	matches := handlePattern.MatchString(handle)
	if !matches {
		return errz.Errorf(msg, handle)
	}

	return nil
}

// IsValidHandle returns false if handle is not a valid handle.
//
// See also: ValidHandle.
func IsValidHandle(handle string) bool {
	return handlePattern.MatchString(handle)
}

// validTableName returns an error if table is not an
// acceptable table name. Valid input must match:
//
//	\A[a-zA-Z_][a-zA-Z0-9_]*$`
func validTableName(table string) error {
	const msg = `invalid table name: %s`

	matches := tablePattern.MatchString(table)
	if !matches {
		return errz.Errorf(msg, table)
	}
	return nil
}

// IsValidGroup returns true if group is a valid group.
// Examples:
//
//	/
//	prod
//	prod/customer
//	prod/customer/pg
//
// Note that "/" is a special case, representing the root group.
func IsValidGroup(group string) bool {
	if group == "" || group == "/" {
		return true
	}

	return groupPattern.MatchString(group)
}

// ValidGroup returns an error if group is not a valid group name.
func ValidGroup(group string) error {
	if !IsValidGroup(group) {
		return errz.Errorf("invalid group: %s", group)
	}

	return nil
}

// handleTypeAliases is a map of type names to the
// more user-friendly suffix returned by SuggestHandle.
var handleTypeAliases = map[string]string{
	typeSL3.String(): "sqlite",
	typePg.String():  "pg",
	typeMS.String():  "mssql",
	typeMy.String():  "my",
}

// SuggestHandle suggests a handle based on location and type.
// If typ is TypeNone, the type will be inferred from loc.
// The takenFn is used to determine if a suggested handle
// is free to be used (e.g. "@csv/sakila" -> "@csv/sakila1", etc).
//
// If the base name (derived from loc) contains illegal handle runes,
// those are replaced with underscore. If the handle would start with
// a number or underscore, it will be prefixed with "h" (for "handle").
// Thus "123.xlsx" becomes "@h123_xlsx".
func SuggestHandle(srcs *Set, typ Type, loc string) (string, error) {
	ploc, err := parseLoc(loc)
	if err != nil {
		return "", err
	}

	if typ == TypeNone {
		typ = ploc.typ
	}

	// use the type name as the _ext suffix if possible
	ext := typ.String()
	if ext == "" {
		if len(ploc.ext) > 0 {
			ext = ploc.ext[1:] // trim the leading period loc ".xlsx" etc
		}
	}

	if alias, ok := handleTypeAliases[ext]; ok {
		ext = alias
	}
	// make sure there's nothing funky loc ext or name
	ext = stringz.SanitizeAlphaNumeric(ext, '_')
	// NOTE: We used to utilize ext in the suggested handle name,
	// e.g. "@actor_csv". With the advent of source groups, we now
	// use the active group instead, e.g. "@prod/actor". So, it's
	// probably safe to rip out all the ext stuff, although maybe
	// UX reports will suggest that "@prod/csv/actor" is preferable,
	// and thus we would still need ext.
	_ = ext
	name := stringz.SanitizeAlphaNumeric(ploc.name, '_')

	// if the name is empty, we use "h" (for "handle"), e.g "@h".
	if name == "" {
		name = "h"
	} else if !unicode.IsLetter([]rune(name)[0]) {
		// If the first rune is not a letter, we prepend "h".
		// So "123" becomes "h123", or "_123" becomes "h_123".
		name = "h" + name
	}

	g := srcs.ActiveGroup()
	switch g {
	case "/", "":
		g = ""
	default:
		g += "/"
	}

	base := "@" + g + name

	// Beginning with base as candidate, check if
	// candidate is taken; if so, append N, where
	// N is a count starting at 1. For example:
	//
	//  @actor
	//  @actor2
	//  @actor3
	candidate := base
	count := 1
	for {
		if count > 1 {
			candidate = base + strconv.Itoa(count)
		}

		if !srcs.IsExistingSource(candidate) && !srcs.IsExistingGroup(candidate[1:]) {
			return candidate, nil
		}

		count++
	}
}

// ParseTableHandle attempts to parse a SLQ source handle and/or table name.
// Surrounding whitespace is trimmed. Examples of valid input values are:
//
//	@handle.tblName
//	@handle
//	.tblName
func ParseTableHandle(input string) (handle, table string, err error) {
	trimmed := strings.TrimSpace(input)
	if trimmed == "" {
		return "", "", errz.New("empty input")
	}

	if strings.Contains(trimmed, ".") {
		if trimmed[0] == '.' {
			// starts with a period; so it's only the table name
			err = validTableName(trimmed[1:])
			if err != nil {
				return "", "", err
			}
			return "", trimmed[1:], nil
		}

		// input contains both handle and table
		parts := strings.Split(trimmed, ".")
		if len(parts) != 2 {
			return "", "", errz.Errorf("invalid handle/table input: %s", input)
		}

		err = ValidHandle(parts[0])
		if err != nil {
			return "", "", err
		}

		err = validTableName(parts[1])
		if err != nil {
			return "", "", err
		}

		return parts[0], parts[1], nil
	}

	// input does not contain a period, therefore it must be a handle by itself
	err = ValidHandle(trimmed)
	if err != nil {
		return "", "", err
	}

	return trimmed, "", err
}

// Contains returns true if srcs contains s, where s is a Source or a source handle.
func Contains[S *Source | ~string](srcs []*Source, s S) bool {
	if len(srcs) == 0 {
		return false
	}

	switch s := any(s).(type) {
	case *Source:
		return slices.Contains(srcs, s)
	case string:
		for i := range srcs {
			if srcs[i] != nil {
				if srcs[i].Handle == s {
					return true
				}
			}
		}
	default:
		// Can never happen
		panic(fmt.Sprintf("unknown type %T: %v", s, s))
	}

	return false
}