package semver

import (
	"errors"
	"fmt"
	"strconv"
	"strings"
)

const (
	numbers  string = "0123456789"
	alphas          = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-"
	alphanum        = alphas + numbers
	dot             = "."
	hyphen          = "-"
	plus            = "+"
)

// Latest fully supported spec version
var SPEC_VERSION = Version{
	Major: 2,
	Minor: 0,
	Patch: 0,
}

type Version struct {
	Major uint64
	Minor uint64
	Patch uint64
	Pre   []*PRVersion
	Build []string //No Precendence
}

// Version to string
func (v Version) String() string {
	versionArray := []string{
		strconv.FormatUint(v.Major, 10),
		dot,
		strconv.FormatUint(v.Minor, 10),
		dot,
		strconv.FormatUint(v.Patch, 10),
	}
	if len(v.Pre) > 0 {
		versionArray = append(versionArray, hyphen)
		for i, pre := range v.Pre {
			if i > 0 {
				versionArray = append(versionArray, dot)
			}
			versionArray = append(versionArray, pre.String())
		}
	}
	if len(v.Build) > 0 {
		versionArray = append(versionArray, plus, strings.Join(v.Build, dot))
	}
	return strings.Join(versionArray, "")
}

// Checks if v is greater than o.
func (v Version) GT(o *Version) bool {
	return (v.Compare(o) == 1)
}

// Checks if v is greater than or equal to o.
func (v Version) GTE(o *Version) bool {
	return (v.Compare(o) >= 0)
}

// Checks if v is less than o.
func (v Version) LT(o *Version) bool {
	return (v.Compare(o) == -1)
}

// Checks if v is less than or equal to o.
func (v Version) LTE(o *Version) bool {
	return (v.Compare(o) <= 0)
}

// Compares Versions v to o:
// -1 == v is less than o
// 0 == v is equal to o
// 1 == v is greater than o
func (v Version) Compare(o *Version) int {
	if v.Major != o.Major {
		if v.Major > o.Major {
			return 1
		} else {
			return -1
		}
	}
	if v.Minor != o.Minor {
		if v.Minor > o.Minor {
			return 1
		} else {
			return -1
		}
	}
	if v.Patch != o.Patch {
		if v.Patch > o.Patch {
			return 1
		} else {
			return -1
		}
	}

	// Quick comparison if a version has no prerelease versions
	if len(v.Pre) == 0 && len(o.Pre) == 0 {
		return 0
	} else if len(v.Pre) == 0 && len(o.Pre) > 0 {
		return 1
	} else if len(v.Pre) > 0 && len(o.Pre) == 0 {
		return -1
	} else {

		i := 0
		for ; i < len(v.Pre) && i < len(o.Pre); i++ {
			if comp := v.Pre[i].Compare(o.Pre[i]); comp == 0 {
				continue
			} else if comp == 1 {
				return 1
			} else {
				return -1
			}
		}

		// If all pr versions are the equal but one has further prversion, this one greater
		if i == len(v.Pre) && i == len(o.Pre) {
			return 0
		} else if i == len(v.Pre) && i < len(o.Pre) {
			return -1
		} else {
			return 1
		}

	}
}

// Validates v and returns error in case
func (v Version) Validate() error {
	// Major, Minor, Patch already validated using uint64

	if len(v.Pre) > 0 {
		for _, pre := range v.Pre {
			if !pre.IsNum { //Numeric prerelease versions already uint64
				if len(pre.VersionStr) == 0 {
					return fmt.Errorf("Prerelease can not be empty %q", pre.VersionStr)
				}
				if !containsOnly(pre.VersionStr, alphanum) {
					return fmt.Errorf("Invalid character(s) found in prerelease %q", pre.VersionStr)
				}
			}
		}
	}

	if len(v.Build) > 0 {
		for _, build := range v.Build {
			if len(build) == 0 {
				return fmt.Errorf("Build meta data can not be empty %q", build)
			}
			if !containsOnly(build, alphanum) {
				return fmt.Errorf("Invalid character(s) found in build meta data %q", build)
			}
		}
	}

	return nil
}

// Alias for Parse, parses version string and returns a validated Version or error
func New(s string) (*Version, error) {
	return Parse(s)
}

// Parses version string and returns a validated Version or error
func Parse(s string) (*Version, error) {
	if len(s) == 0 {
		return nil, errors.New("Version string empty")
	}

	// Split into major.minor.(patch+pr+meta)
	parts := strings.SplitN(s, ".", 3)
	if len(parts) != 3 {
		return nil, errors.New("No Major.Minor.Patch elements found")
	}

	// Major
	if !containsOnly(parts[0], numbers) {
		return nil, fmt.Errorf("Invalid character(s) found in major number %q", parts[0])
	}
	if hasLeadingZeroes(parts[0]) {
		return nil, fmt.Errorf("Major number must not contain leading zeroes %q", parts[0])
	}
	major, err := strconv.ParseUint(parts[0], 10, 64)
	if err != nil {
		return nil, err
	}

	// Minor
	if !containsOnly(parts[1], numbers) {
		return nil, fmt.Errorf("Invalid character(s) found in minor number %q", parts[1])
	}
	if hasLeadingZeroes(parts[1]) {
		return nil, fmt.Errorf("Minor number must not contain leading zeroes %q", parts[1])
	}
	minor, err := strconv.ParseUint(parts[1], 10, 64)
	if err != nil {
		return nil, err
	}

	preIndex := strings.Index(parts[2], "-")
	buildIndex := strings.Index(parts[2], "+")

	// Determine last index of patch version (first of pre or build versions)
	var subVersionIndex int
	if preIndex != -1 && buildIndex == -1 {
		subVersionIndex = preIndex
	} else if preIndex == -1 && buildIndex != -1 {
		subVersionIndex = buildIndex
	} else if preIndex == -1 && buildIndex == -1 {
		subVersionIndex = len(parts[2])
	} else {
		// if there is no actual prversion but a hyphen inside the build meta data
		if buildIndex < preIndex {
			subVersionIndex = buildIndex
			preIndex = -1 // Build meta data before preIndex found implicates there are no prerelease versions
		} else {
			subVersionIndex = preIndex
		}
	}

	if !containsOnly(parts[2][:subVersionIndex], numbers) {
		return nil, fmt.Errorf("Invalid character(s) found in patch number %q", parts[2][:subVersionIndex])
	}
	if hasLeadingZeroes(parts[2][:subVersionIndex]) {
		return nil, fmt.Errorf("Patch number must not contain leading zeroes %q", parts[2][:subVersionIndex])
	}
	patch, err := strconv.ParseUint(parts[2][:subVersionIndex], 10, 64)
	if err != nil {
		return nil, err
	}
	v := &Version{}
	v.Major = major
	v.Minor = minor
	v.Patch = patch

	// There are PreRelease versions
	if preIndex != -1 {
		var preRels string
		if buildIndex != -1 {
			preRels = parts[2][subVersionIndex+1 : buildIndex]
		} else {
			preRels = parts[2][subVersionIndex+1:]
		}
		prparts := strings.Split(preRels, ".")
		for _, prstr := range prparts {
			parsedPR, err := NewPRVersion(prstr)
			if err != nil {
				return nil, err
			}
			v.Pre = append(v.Pre, parsedPR)
		}
	}

	// There is build meta data
	if buildIndex != -1 {
		buildStr := parts[2][buildIndex+1:]
		buildParts := strings.Split(buildStr, ".")
		for _, str := range buildParts {
			if len(str) == 0 {
				return nil, errors.New("Build meta data is empty")
			}
			if !containsOnly(str, alphanum) {
				return nil, fmt.Errorf("Invalid character(s) found in build meta data %q", str)
			}
			v.Build = append(v.Build, str)
		}
	}

	return v, nil
}

// PreRelease Version
type PRVersion struct {
	VersionStr string
	VersionNum uint64
	IsNum      bool
}

// Creates a new valid prerelease version
func NewPRVersion(s string) (*PRVersion, error) {
	if len(s) == 0 {
		return nil, errors.New("Prerelease is empty")
	}
	v := &PRVersion{}
	if containsOnly(s, numbers) {
		if hasLeadingZeroes(s) {
			return nil, fmt.Errorf("Numeric PreRelease version must not contain leading zeroes %q", s)
		}
		num, err := strconv.ParseUint(s, 10, 64)

		// Might never be hit, but just in case
		if err != nil {
			return nil, err
		}
		v.VersionNum = num
		v.IsNum = true
	} else if containsOnly(s, alphanum) {
		v.VersionStr = s
		v.IsNum = false
	} else {
		return nil, fmt.Errorf("Invalid character(s) found in prerelease %q", s)
	}
	return v, nil
}

// Is pre release version numeric?
func (v PRVersion) IsNumeric() bool {
	return v.IsNum
}

// Compares PreRelease Versions v to o:
// -1 == v is less than o
// 0 == v is equal to o
// 1 == v is greater than o
func (v PRVersion) Compare(o *PRVersion) int {
	if v.IsNum && !o.IsNum {
		return -1
	} else if !v.IsNum && o.IsNum {
		return 1
	} else if v.IsNum && o.IsNum {
		if v.VersionNum == o.VersionNum {
			return 0
		} else if v.VersionNum > o.VersionNum {
			return 1
		} else {
			return -1
		}
	} else { // both are Alphas
		if v.VersionStr == o.VersionStr {
			return 0
		} else if v.VersionStr > o.VersionStr {
			return 1
		} else {
			return -1
		}
	}
}

// PreRelease version to string
func (v PRVersion) String() string {
	if v.IsNum {
		return strconv.FormatUint(v.VersionNum, 10)
	}
	return v.VersionStr
}

func containsOnly(s string, set string) bool {
	return strings.IndexFunc(s, func(r rune) bool {
		return !strings.ContainsRune(set, r)
	}) == -1
}

func hasLeadingZeroes(s string) bool {
	return len(s) > 1 && s[0] == '0'
}

// Creates a new valid build version
func NewBuildVersion(s string) (string, error) {
	if len(s) == 0 {
		return "", errors.New("Buildversion is empty")
	}
	if !containsOnly(s, alphanum) {
		return "", fmt.Errorf("Invalid character(s) found in build meta data %q", s)
	}
	return s, nil
}