package pwgenerator

import (
	"encoding/xml"
	"strings"
	"time"

	"r00t2.io/goutils/multierr"
)

// Generate generates a list of passwords for a GenOpts.
func (o *GenOpts) Generate() (passwords []string, err error) {

	var passwds []string = make([]string, o.Count)
	var charset CharSet
	var errs *multierr.MultiError = multierr.NewMultiError(nil)

	if o.Count == 0 {
		o.Count = DefCount
	}
	if o.LengthMax == 0 {
		o.LengthMax = DefMaxLen
	}

	if err = o.sanChk(); err != nil {
		return
	}

	if charset, err = o.Chars(); err != nil {
		return
	}

	for idx, _ := range passwds {
		if passwds[idx], err = o.generatePassword(charset); err != nil {
			errs.AddError(err)
			err = nil
		}
	}

	passwords = passwds

	if !errs.IsEmpty() {
		err = errs
	}

	return
}

// MustGenerate is like Generate, but will panic on error instead of returning.
func (o *GenOpts) MustGenerate() (passwords []string) {

	var err error

	if passwords, err = o.Generate(); err != nil {
		panic(err)
	}

	return
}

/*
	GenOnce generates a *single* password from a GenOpts.

	This method is particularly useful/convenient if GenOpts.Count is 1
	and you don't want to have to assign to a slice and then get the first index.
*/
func (o GenOpts) GenerateOnce() (password string, err error) {

	var passwds []string

	o.Count = 1
	if passwds, err = o.Generate(); err != nil {
		return
	}
	password = passwds[0]

	return
}

// MustGenerateOnce is like GenerateOnce, but will panic on error instead of returning.
func (o *GenOpts) MustGenerateOnce() (password string) {

	var err error

	if password, err = o.GenerateOnce(); err != nil {
		panic(err)
	}

	return
}

/*
	GenerateCollection returns a PwCollection instead of a slice of password text.

	It contains extended information about a password, hashes, etc.

	Note: hashing support currently under construction and not implemented. TODO.
*/
func (o *GenOpts) GenerateCollection(hashAlgos []pwHash) (collection *PwCollection, err error) {

	var charset CharSet
	var errs *multierr.MultiError = multierr.NewMultiError(nil)
	var passwd string

	collection = &PwCollection{
		XMLName: xml.Name{
			Space: "", // TODO?
			Local: "collection",
		},
		Passwords: make([]*PwDef, o.Count),
	}

	if o.Count == 0 {
		o.Count = DefCount
	}
	if o.LengthMax == 0 {
		o.LengthMax = DefMaxLen
	}

	if err = o.sanChk(); err != nil {
		return
	}

	if charset, err = o.Chars(); err != nil {
		return
	}

	for idx, _ := range collection.Passwords {
		if passwd, err = o.generatePassword(charset); err != nil {
			errs.AddError(err)
			err = nil
		}
		collection.Passwords[idx] = &PwDef{
			XMLName: xml.Name{
				Space: "", // TODO?
				Local: "password",
			},
			Password:  passwd,
			Generated: time.Now(),
			Hashes:    nil, // TODO
		}
	}

	return
}

// generatePassword generates a single password from CharSet c (plus any minimum requirements).
func (o *GenOpts) generatePassword(c CharSet) (password string, err error) {

	var trueMinLen uint
	var passLenGap uint
	var passLen int
	var passAlloc []rune
	var filter *selectFilter = o.getFilter()
	var isDisabled bool

	if err = o.sanChk(); err != nil {
		return
	}

	// Defaults.
	trueMinLen = o.LengthMin
	if trueMinLen == 0 {
		trueMinLen = DefMinLin
	}

	// Get a fixed password length...
	passLenGap = o.LengthMax - trueMinLen
	if passLen, err = saferRandInt(int(passLenGap)); err != nil {
		return
	}
	passLen = passLen + int(trueMinLen) // (We need to re-add; it was subtracted above to get a zero-shifted number for start in saferRandInt.)
	// And make the rune slice of that length.
	passAlloc = make([]rune, passLen)

	idx := 0
	for idx < passLen {
		var char Char

		if o.explicitCharset != nil && len(o.explicitCharset) != 0 {
			// Add upperCounter chars (if necessary).
			for filter.upperCounter > 0 {
				if char, err = upper.RandChar(); err != nil {
					continue
				}
				if isDisabled, err = o.DisabledChars.Has(char); err != nil || isDisabled {
					err = nil
					continue
				}
				passAlloc[idx] = rune(char)
				filter.upperCounter--
				idx++
				continue
			}
			// Add lowerCounter chars (if necessary).
			for filter.lowerCounter > 0 {
				if char, err = lower.RandChar(); err != nil {
					continue
				}
				if isDisabled, err = o.DisabledChars.Has(char); err != nil || isDisabled {
					err = nil
					continue
				}
				passAlloc[idx] = rune(char)
				filter.lowerCounter--
				idx++
				continue
			}
			// Add numberCounter chars (if necessary).
			for filter.numberCounter > 0 {
				if char, err = numeric.RandChar(); err != nil {
					continue
				}
				if isDisabled, err = o.DisabledChars.Has(char); err != nil || isDisabled {
					err = nil
					continue
				}
				passAlloc[idx] = rune(char)
				filter.numberCounter--
				idx++
				continue
			}
			// Add symbolCounter chars (if necessary).
			for filter.symbolCounter > 0 {
				if char, err = symbols.RandChar(); err != nil {
					continue
				}
				if isDisabled, err = o.DisabledChars.Has(char); err != nil || isDisabled {
					err = nil
					continue
				}
				passAlloc[idx] = rune(char)
				filter.symbolCounter--
				idx++
				continue
			}
			// Add extendedCounter chars (if necessary).
			for filter.extendedCounter > 0 {
				if char, err = extendedSymbols.RandChar(); err != nil {
					continue
				}
				if isDisabled, err = o.DisabledChars.Has(char); err != nil || isDisabled {
					err = nil
					continue
				}
				passAlloc[idx] = rune(char)
				filter.extendedCounter--
				idx++
				continue
			}

			// Break here if we've reached the full password with just the filter.
			if idx > passLen {
				err = ErrTooSmall
				return
			} else if idx == passLen {
				break
			}
		}

		// Minimum requirements satisfied; continue with default GenOpts-specific charset.
		for {

			if char, err = c.RandChar(); err != nil {
				return
			}
			if isDisabled, err = o.DisabledChars.Has(char); err != nil || isDisabled {
				err = nil
				continue
			}

			passAlloc[idx] = rune(char)
			idx++
			break
		}
	}

	password = string(passAlloc)
	passwordShuffle(&password)

	return
}

// Chars returns the list of evaluated characters that would be used in a GenOpts.
func (o *GenOpts) Chars() (chars CharSet, err error) {

	chars = make(CharSet, 0)

	if err = o.sanChk(); err != nil {
		return
	}

	if o.explicitCharset != nil && len(o.explicitCharset) != 0 {
		chars = o.explicitCharset
		return
	}

	if o.Alpha {
		chars = append(chars, alpha...)
	}
	if o.Numeric {
		chars = append(chars, numeric...)
	}
	if o.Symbols {
		chars = append(chars, symbols...)
	}
	if o.ExtendedSymbols {
		chars = append(chars, extendedSymbols...)
	}

	if chars == nil || len(chars) == 0 {
		err = ErrEmptyCharsets
		return
	}

	return
}

/*
	SetExplicitCharset sets a GenOpts' charset to an explicit selection. It is deduplicated before being used unless inclDupes is true.
	(Duplicate runes can be used to increase the likelihood of specific characters.)

	Note that if an explicit charset is defined, the following opts will have NO effect:

			Alpha
			Numeric
			Symbols
			ExtendedSymbols
			CountUpper
			CountLower
			CountSymbols
			CountExtended
			DisabledChars

	To have these fields be used again, call GenOpts.UnsetExplicitCharset.

	chars can be a CharSet, []rune, []byte, []string, or string
*/
func (o *GenOpts) SetExplicitCharset(chars interface{}, inclDupes bool) (err error) {

	var charset CharSet

	switch t := chars.(type) {
	case []rune:
		charset = CharSet(string(t))
	case []byte:
		charset = CharSet(string(t))
	case []string:
		s := strings.Join(t, "")
		charset = CharSet(s)
	case string:
		charset = CharSet(t)
	default:
		err = ErrBadType
		return
	}

	if !inclDupes {
		sortDedupe(&charset)
	}

	o.explicitCharset = charset

	return
}

/*
	UnsetExplicitCharset removes the explicit charset used for generation and instead uses the fields specified in the actual GenOpts.

	See GenOpts.SetExplicitCharset for more details.
*/
func (o *GenOpts) UnsetExplicitCharset() {

	o.explicitCharset = nil

	return
}

// getFilter gets a filter counter.
func (o *GenOpts) getFilter() (f *selectFilter) {

	f = &selectFilter{
		upperCounter:    o.CountUpper,
		lowerCounter:    o.CountLower,
		numberCounter:   o.CountNumbers,
		symbolCounter:   o.CountSymbols,
		extendedCounter: o.CountExtended,
	}

	return
}

func (o *GenOpts) sanChk() (err error) {

	var maxMin uint

	// Sanity checks/error conditions.
	if o.explicitCharset != nil && len(o.explicitCharset) != 0 {
		if o.CountUpper > 0 && !o.Alpha {
			err = ErrIncompatCharsetFilter
			return
		}
		if o.CountLower > 0 && !o.Alpha {
			err = ErrIncompatCharsetFilter
			return
		}
		if o.CountNumbers > 0 && !o.Numeric {
			err = ErrIncompatCharsetFilter
			return
		}
		if o.CountSymbols > 0 && !o.Symbols {
			err = ErrIncompatCharsetFilter
			return
		}
		if o.CountExtended > 0 && !o.ExtendedSymbols {
			err = ErrIncompatCharsetFilter
			return
		}
	}
	maxMin = o.CountUpper + o.CountLower + o.CountNumbers + o.CountSymbols + o.CountExtended
	if maxMin > o.LengthMax {
		err = ErrTooSmall
		return
	}
	if o.LengthMin > o.LengthMax {
		err = ErrSwitchedLenLimits
		return
	}

	return
}