package core

import (
	"strings"
	"sync"
)

// name translation between struct, fields names and table, column names
type IMapper interface {
	Obj2Table(string) string
	Table2Obj(string) string
}

type CacheMapper struct {
	oriMapper      IMapper
	obj2tableCache map[string]string
	obj2tableMutex sync.RWMutex
	table2objCache map[string]string
	table2objMutex sync.RWMutex
}

func NewCacheMapper(mapper IMapper) *CacheMapper {
	return &CacheMapper{oriMapper: mapper, obj2tableCache: make(map[string]string),
		table2objCache: make(map[string]string),
	}
}

func (m *CacheMapper) Obj2Table(o string) string {
	m.obj2tableMutex.RLock()
	t, ok := m.obj2tableCache[o]
	m.obj2tableMutex.RUnlock()
	if ok {
		return t
	}

	t = m.oriMapper.Obj2Table(o)
	m.obj2tableMutex.Lock()
	m.obj2tableCache[o] = t
	m.obj2tableMutex.Unlock()
	return t
}

func (m *CacheMapper) Table2Obj(t string) string {
	m.table2objMutex.RLock()
	o, ok := m.table2objCache[t]
	m.table2objMutex.RUnlock()
	if ok {
		return o
	}

	o = m.oriMapper.Table2Obj(t)
	m.table2objMutex.Lock()
	m.table2objCache[t] = o
	m.table2objMutex.Unlock()
	return o
}

// SameMapper implements IMapper and provides same name between struct and
// database table
type SameMapper struct {
}

func (m SameMapper) Obj2Table(o string) string {
	return o
}

func (m SameMapper) Table2Obj(t string) string {
	return t
}

// SnakeMapper implements IMapper and provides name transaltion between
// struct and database table
type SnakeMapper struct {
}

func snakeCasedName(name string) string {
	newstr := make([]rune, 0)
	for idx, chr := range name {
		if isUpper := 'A' <= chr && chr <= 'Z'; isUpper {
			if idx > 0 {
				newstr = append(newstr, '_')
			}
			chr -= ('A' - 'a')
		}
		newstr = append(newstr, chr)
	}

	return string(newstr)
}

/*func pascal2Sql(s string) (d string) {
    d = ""
    lastIdx := 0
    for i := 0; i < len(s); i++ {
        if s[i] >= 'A' && s[i] <= 'Z' {
            if lastIdx < i {
                d += s[lastIdx+1 : i]
            }
            if i != 0 {
                d += "_"
            }
            d += string(s[i] + 32)
            lastIdx = i
        }
    }
    d += s[lastIdx+1:]
    return
}*/

func (mapper SnakeMapper) Obj2Table(name string) string {
	return snakeCasedName(name)
}

func titleCasedName(name string) string {
	newstr := make([]rune, 0)
	upNextChar := true

	name = strings.ToLower(name)

	for _, chr := range name {
		switch {
		case upNextChar:
			upNextChar = false
			if 'a' <= chr && chr <= 'z' {
				chr -= ('a' - 'A')
			}
		case chr == '_':
			upNextChar = true
			continue
		}

		newstr = append(newstr, chr)
	}

	return string(newstr)
}

func (mapper SnakeMapper) Table2Obj(name string) string {
	return titleCasedName(name)
}

// provide prefix table name support
type PrefixMapper struct {
	Mapper IMapper
	Prefix string
}

func (mapper PrefixMapper) Obj2Table(name string) string {
	return mapper.Prefix + mapper.Mapper.Obj2Table(name)
}

func (mapper PrefixMapper) Table2Obj(name string) string {
	return mapper.Mapper.Table2Obj(name[len(mapper.Prefix):])
}

func NewPrefixMapper(mapper IMapper, prefix string) PrefixMapper {
	return PrefixMapper{mapper, prefix}
}

// provide suffix table name support
type SuffixMapper struct {
	Mapper IMapper
	Suffix string
}

func (mapper SuffixMapper) Obj2Table(name string) string {
	return mapper.Mapper.Obj2Table(name) + mapper.Suffix
}

func (mapper SuffixMapper) Table2Obj(name string) string {
	return mapper.Mapper.Table2Obj(name[:len(name)-len(mapper.Suffix)])
}

func NewSuffixMapper(mapper IMapper, suffix string) SuffixMapper {
	return SuffixMapper{mapper, suffix}
}