package pkgbuild

import (
	"bytes"
	"fmt"
	"io/ioutil"
	"strconv"
	"strings"
)

// Dependency describes a dependency with min and max version, if any.
type Dependency struct {
	Name   string           // dependency name
	MinVer *CompleteVersion // min version
	sgt    bool             // defines if min version is strictly greater than
	MaxVer *CompleteVersion // max version
	slt    bool             // defines if max version is strictly less than
}

// Restrict merges two dependencies together into a new dependency where the
// conditions of both a and b are met
func (a *Dependency) Restrict(b *Dependency) *Dependency {
	newDep := &Dependency{
		Name: a.Name,
	}

	if a.MaxVer != nil || b.MaxVer != nil {
		newDep.MaxVer = &CompleteVersion{}

		if a.MaxVer == nil {
			*newDep.MaxVer = *b.MaxVer
			newDep.slt = b.slt
		} else if b.MaxVer == nil {
			*newDep.MaxVer = *a.MaxVer
			newDep.slt = a.slt
		} else {
			cmpMax := a.MaxVer.cmp(b.MaxVer)
			if cmpMax >= 1 {
				*newDep.MaxVer = *b.MaxVer
				newDep.slt = b.slt
			} else if cmpMax <= -1 {
				*newDep.MaxVer = *a.MaxVer
				newDep.slt = a.slt
			} else if cmpMax == 0 {
				if len(a.MaxVer.Pkgrel) > len(b.MaxVer.Pkgrel) {
					*newDep.MaxVer = *a.MaxVer
				} else {
					*newDep.MaxVer = *b.MaxVer
				}
				if a.slt != b.slt {
					newDep.slt = true
				} else {
					newDep.slt = a.slt
				}
			}
		}
	}

	if a.MinVer != nil || b.MinVer != nil {
		newDep.MinVer = &CompleteVersion{}

		if a.MinVer == nil {
			*newDep.MinVer = *b.MinVer
			newDep.sgt = b.slt
		} else if b.MinVer == nil {
			*newDep.MinVer = *a.MinVer
			newDep.sgt = a.sgt
		} else {
			cmpMin := a.MinVer.cmp(b.MinVer)
			if cmpMin >= 1 {
				*newDep.MinVer = *a.MinVer
				newDep.sgt = a.sgt
			} else if cmpMin <= -1 {
				*newDep.MinVer = *b.MinVer
				newDep.sgt = b.sgt
			} else if cmpMin == 0 {
				if len(a.MinVer.Pkgrel) > len(b.MinVer.Pkgrel) {
					*newDep.MinVer = *a.MinVer
				} else {
					*newDep.MinVer = *b.MinVer
				}
				if a.sgt != b.sgt {
					newDep.sgt = true
				} else {
					newDep.sgt = a.sgt
				}
			}
		}
	}

	return newDep
}

func (dep *Dependency) String() string {
	str := ""
	greaterThan := ">"
	lessThan := "<"

	if !dep.sgt {
		greaterThan = ">="
	}

	if !dep.slt {
		lessThan = "<="
	}

	if dep.MinVer != nil {
		str += dep.Name + greaterThan + dep.MinVer.String()

		if dep.MaxVer != nil {
			str += " "
		}
	}

	if dep.MaxVer != nil {
		str += dep.Name + lessThan + dep.MaxVer.String()
	}

	return str
}

// PKGBUILD is a struct describing a parsed PKGBUILD file.
// Required fields are:
//	pkgname
//	pkgver
//	pkgrel
//	arch
//	(license) - not required but recommended
//
// parsing a PKGBUILD file without these fields will fail
type PKGBUILD struct {
	Pkgnames     []string
	Pkgver       Version // required
	Pkgrel       Version // required
	Pkgdir       string
	Epoch        int
	Pkgbase      string
	Pkgdesc      string
	Arch         []string // required
	URL          string
	License      []string // recommended
	Groups       []string
	Depends      []*Dependency
	Optdepends   []string
	Makedepends  []*Dependency
	Checkdepends []*Dependency
	Provides     []string
	Conflicts    []string
	Replaces     []string
	Backup       []string
	Options      []string
	Install      string
	Changelog    string
	Source       []string
	Noextract    []string
	Md5sums      []string
	Sha1sums     []string
	Sha224sums   []string
	Sha256sums   []string
	Sha384sums   []string
	Sha512sums   []string
	Validpgpkeys []string
}

// Newer is true if p has a higher version number than p2
func (p *PKGBUILD) Newer(p2 *PKGBUILD) bool {
	if p.Epoch < p2.Epoch {
		return false
	}

	if p.Pkgver.bigger(p2.Pkgver) {
		return true
	}

	if p2.Pkgver.bigger(p.Pkgver) {
		return false
	}

	return p.Pkgrel > p2.Pkgrel
}

// Older is true if p has a smaller version number than p2
func (p *PKGBUILD) Older(p2 *PKGBUILD) bool {
	if p.Epoch < p2.Epoch {
		return true
	}

	if p2.Pkgver.bigger(p.Pkgver) {
		return true
	}

	if p.Pkgver.bigger(p2.Pkgver) {
		return false
	}

	return p.Pkgrel < p2.Pkgrel
}

// Version returns the full version of the PKGBUILD (including epoch and rel)
func (p *PKGBUILD) Version() string {
	if p.Epoch > 0 {
		return fmt.Sprintf("%d:%s-%s", p.Epoch, p.Pkgver, p.Pkgrel)
	}

	return fmt.Sprintf("%s-%s", p.Pkgver, p.Pkgrel)
}

// CompleteVersion returns a Complete version struct including version, rel and
// epoch.
func (p *PKGBUILD) CompleteVersion() CompleteVersion {
	return CompleteVersion{
		Version: p.Pkgver,
		Epoch:   uint8(p.Epoch),
		Pkgrel:  p.Pkgrel,
	}
}

// BuildDepends is Depends, MakeDepends and CheckDepends combined.
func (p *PKGBUILD) BuildDepends() []*Dependency {
	// TODO real merge
	deps := make([]*Dependency, len(p.Depends)+len(p.Makedepends)+len(p.Checkdepends))

	deps = append(p.Depends, p.Makedepends...)
	deps = append(deps, p.Checkdepends...)

	return deps
}

// IsDevel returns true if package contains devel packages (-{bzr,git,svn,hg})
// TODO: more robust check.
func (p *PKGBUILD) IsDevel() bool {
	for _, name := range p.Pkgnames {
		if strings.HasSuffix(name, "-git") {
			return true
		}

		if strings.HasSuffix(name, "-svn") {
			return true
		}

		if strings.HasSuffix(name, "-hg") {
			return true
		}

		if strings.HasSuffix(name, "-bzr") {
			return true
		}
	}

	return false
}

// MustParseSRCINFO must parse the .SRCINFO given by path or it will panic
func MustParseSRCINFO(path string) *PKGBUILD {
	pkgbuild, err := ParseSRCINFO(path)
	if err != nil {
		panic(err)
	}
	return pkgbuild
}

// ParseSRCINFO parses .SRCINFO file given by path.
// This is a safe alternative to ParsePKGBUILD given that a .SRCINFO file is
// available
func ParseSRCINFO(path string) (*PKGBUILD, error) {
	f, err := ioutil.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("unable to read file: %s, %s", path, err.Error())
	}

	return parsePKGBUILD(string(f))
}

// ParseSRCINFOContent parses a .SRCINFO formatted byte slice.
// This is a safe alternative to ParsePKGBUILD given that the .SRCINFO content
// is available
func ParseSRCINFOContent(content []byte) (*PKGBUILD, error) {
	return parsePKGBUILD(string(content))
}

// parse a PKGBUILD and check that the required fields has a non-empty value
func parsePKGBUILD(input string) (*PKGBUILD, error) {
	pkgb, err := parse(input)
	if err != nil {
		return nil, err
	}

	if !validPkgver(string(pkgb.Pkgver)) {
		return nil, fmt.Errorf("invalid pkgver: %s", pkgb.Pkgver)
	}

	if len(pkgb.Arch) == 0 {
		return nil, fmt.Errorf("Arch missing")
	}

	if len(pkgb.Pkgnames) == 0 {
		return nil, fmt.Errorf("missing pkgname")
	}

	for _, name := range pkgb.Pkgnames {
		if !validPkgname(name) {
			return nil, fmt.Errorf("invalid pkgname: %s", name)
		}
	}

	return pkgb, nil
}

// parses a SRCINFO formatted PKGBUILD
func parse(input string) (*PKGBUILD, error) {
	var pkgbuild *PKGBUILD
	var next item

	lexer := lex(input)
Loop:
	for {
		token := lexer.nextItem()

		// strip arch from source_arch like constructs
		witharch := strings.SplitN(token.val, "_", 2)
		if len(witharch) == 2 {
			found := false
			for _, arch := range pkgbuild.Arch {
				if arch == witharch[1] {
					token.val = witharch[0]
					found = true
					break
				}
			}

			if !found {
				return nil, fmt.Errorf("unsupported arch for variable: %s", token.val)
			}
		}

		switch token.typ {
		case itemPkgbase:
			next = lexer.nextItem()
			pkgbuild = &PKGBUILD{Epoch: 0, Pkgbase: next.val}
		case itemPkgname:
			next = lexer.nextItem()
			pkgbuild.Pkgnames = append(pkgbuild.Pkgnames, next.val)
		case itemPkgver:
			next = lexer.nextItem()
			version, err := parseVersion(next.val)
			if err != nil {
				return nil, err
			}
			pkgbuild.Pkgver = version
		case itemPkgrel:
			next = lexer.nextItem()
			rel, err := parseVersion(next.val)
			if err != nil {
				return nil, err
			}
			pkgbuild.Pkgrel = rel
		case itemPkgdir:
			next = lexer.nextItem()
			pkgbuild.Pkgdir = next.val
		case itemEpoch:
			next = lexer.nextItem()
			epoch, err := strconv.ParseInt(next.val, 10, 0)
			if err != nil {
				return nil, err
			}

			if epoch < 0 {
				return nil, fmt.Errorf("invalid epoch: %d", epoch)
			}
			pkgbuild.Epoch = int(epoch)
		case itemPkgdesc:
			next = lexer.nextItem()
			pkgbuild.Pkgdesc = next.val
		case itemArch:
			next = lexer.nextItem()
			pkgbuild.Arch = append(pkgbuild.Arch, next.val)
		case itemURL:
			next = lexer.nextItem()
			pkgbuild.URL = next.val
		case itemLicense:
			next = lexer.nextItem()
			pkgbuild.License = append(pkgbuild.License, next.val)
		case itemGroups:
			next = lexer.nextItem()
			pkgbuild.Groups = append(pkgbuild.Groups, next.val)
		case itemDepends:
			next = lexer.nextItem()
			deps, err := parseDependency(next.val, pkgbuild.Depends)
			if err != nil {
				return nil, err
			}
			pkgbuild.Depends = deps
		case itemOptdepends:
			next = lexer.nextItem()
			pkgbuild.Optdepends = append(pkgbuild.Optdepends, next.val)
		case itemMakedepends:
			next = lexer.nextItem()
			deps, err := parseDependency(next.val, pkgbuild.Makedepends)
			if err != nil {
				return nil, err
			}
			pkgbuild.Makedepends = deps
		case itemCheckdepends:
			next = lexer.nextItem()
			deps, err := parseDependency(next.val, pkgbuild.Checkdepends)
			if err != nil {
				return nil, err
			}
			pkgbuild.Checkdepends = deps
		case itemProvides:
			next = lexer.nextItem()
			pkgbuild.Provides = append(pkgbuild.Provides, next.val)
		case itemConflicts:
			next = lexer.nextItem()
			pkgbuild.Conflicts = append(pkgbuild.Conflicts, next.val)
		case itemReplaces:
			next = lexer.nextItem()
			pkgbuild.Replaces = append(pkgbuild.Replaces, next.val)
		case itemBackup:
			next = lexer.nextItem()
			pkgbuild.Backup = append(pkgbuild.Backup, next.val)
		case itemOptions:
			next = lexer.nextItem()
			pkgbuild.Options = append(pkgbuild.Options, next.val)
		case itemInstall:
			next = lexer.nextItem()
			pkgbuild.Install = next.val
		case itemChangelog:
			next = lexer.nextItem()
			pkgbuild.Changelog = next.val
		case itemSource:
			next = lexer.nextItem()
			pkgbuild.Source = append(pkgbuild.Source, next.val)
		case itemNoextract:
			next = lexer.nextItem()
			pkgbuild.Noextract = append(pkgbuild.Noextract, next.val)
		case itemMd5sums:
			next = lexer.nextItem()
			pkgbuild.Md5sums = append(pkgbuild.Md5sums, next.val)
		case itemSha1sums:
			next = lexer.nextItem()
			pkgbuild.Sha1sums = append(pkgbuild.Sha1sums, next.val)
		case itemSha224sums:
			next = lexer.nextItem()
			pkgbuild.Sha224sums = append(pkgbuild.Sha224sums, next.val)
		case itemSha256sums:
			next = lexer.nextItem()
			pkgbuild.Sha256sums = append(pkgbuild.Sha256sums, next.val)
		case itemSha384sums:
			next = lexer.nextItem()
			pkgbuild.Sha384sums = append(pkgbuild.Sha384sums, next.val)
		case itemSha512sums:
			next = lexer.nextItem()
			pkgbuild.Sha512sums = append(pkgbuild.Sha512sums, next.val)
		case itemValidpgpkeys:
			next = lexer.nextItem()
			pkgbuild.Validpgpkeys = append(pkgbuild.Validpgpkeys, next.val)
		case itemEndSplit:
		case itemError:
			return nil, fmt.Errorf(token.val)
		case itemEOF:
			break Loop
		default:
			return nil, fmt.Errorf("invalid variable: %s", token.val)
		}
	}
	return pkgbuild, nil
}

// parse and validate a version string
func parseVersion(s string) (Version, error) {
	if validPkgver(s) {
		return Version(s), nil
	}

	return "", fmt.Errorf("invalid version string: %s", s)
}

// check if name is a valid pkgname format
func validPkgname(name string) bool {
	if len(name) < 1 {
		return false
	}

	if name[0] == '-' {
		return false
	}

	for _, r := range name {
		if !isValidPkgnameChar(r) {
			return false
		}
	}

	return true
}

// check if version is a valid pkgver format
func validPkgver(version string) bool {
	if len(version) < 1 {
		return false
	}

	if !isAlphaNumeric(rune(version[0])) {
		return false
	}

	for _, r := range version[1:] {
		if !isValidPkgverChar(r) {
			return false
		}
	}

	return true
}

// ParseDeps parses a string slice of dependencies into a slice of Dependency
// objects.
func ParseDeps(deps []string) ([]*Dependency, error) {
	var err error
	dependencies := make([]*Dependency, 0)

	for _, dep := range deps {
		dependencies, err = parseDependency(dep, dependencies)
		if err != nil {
			return nil, err
		}
	}

	return dependencies, nil
}

// parse dependency with possible version restriction
func parseDependency(dep string, deps []*Dependency) ([]*Dependency, error) {
	var name string
	var dependency *Dependency
	index := -1

	if dep == "" {
		return deps, nil
	}

	if dep[0] == '-' {
		return nil, fmt.Errorf("invalid dependency name")
	}

	i := 0
	for _, c := range dep {
		if !isValidPkgnameChar(c) {
			break
		}
		i++
	}

	// check if the dependency has been set before
	name = dep[0:i]
	for n, d := range deps {
		if d.Name == name {
			index = n
			break
		}
	}

	dependency = &Dependency{
		Name: name,
		sgt:  false,
		slt:  false,
	}

	if len(dep) != len(name) {
		var eq bytes.Buffer
		for _, c := range dep[i:] {
			if c == '<' || c == '>' || c == '=' {
				i++
				eq.WriteRune(c)
				continue
			}
			break
		}

		version, err := NewCompleteVersion(dep[i:])
		if err != nil {
			return nil, err
		}

		switch eq.String() {
		case "=":
			dependency.MinVer = version
			dependency.MaxVer = version
		case "<=":
			dependency.MaxVer = version
		case ">=":
			dependency.MinVer = version
		case "<":
			dependency.MaxVer = version
			dependency.slt = true
		case ">":
			dependency.MinVer = version
			dependency.sgt = true
		}
	}

	if index == -1 {
		deps = append(deps, dependency)
	} else {
		deps[index] = deps[index].Restrict(dependency)
	}

	return deps, nil
}

// isLowerAlpha reports whether c is a lowercase alpha character
func isLowerAlpha(c rune) bool {
	return 'a' <= c && c <= 'z'
}

// check if c is a valid pkgname char
func isValidPkgnameChar(c rune) bool {
	return isLowerAlpha(c) || isDigit(c) || c == '@' || c == '.' || c == '_' || c == '+' || c == '-'
}

// check if c is a valid pkgver char
func isValidPkgverChar(c rune) bool {
	return isAlphaNumeric(c) || c == '_' || c == '+' || c == '.' || c == '~'
}