package mkcompare

import (
	"bufio"
	"fmt"
	"github.com/google/go-cmp/cmp"
	"io"
	"regexp"
	"sort"
	"strings"
)

type MkVariable struct {
	Name  string
	Value string
}

type MkModule struct {
	Type      string
	Location  int
	Extras    int
	Variables map[string]string
}

type MkFile struct {
	Path    string
	Modules map[string]*MkModule
}

type myScanner struct {
	*bufio.Scanner
	lineNo int
}

func (s *myScanner) Scan() bool {
	if s.Scanner.Scan() {
		s.lineNo = s.lineNo + 1
		return true
	}
	return false
}

var (
	rexEmpty   = regexp.MustCompile("^ *$")
	rexHeader  = regexp.MustCompile("^include +\\Q$(CLEAR_VARS)\\E *(# *(.*))?")
	rexAssign  = regexp.MustCompile("^ *(.*) ([:+])= *(.*)$")
	rexFooter  = regexp.MustCompile("^-?include *(.*)$")
	rexIgnore1 = regexp.MustCompile("\\$\\(call dist-for-goals")
	rexIgnore2 = regexp.MustCompile("\\$\\(LOCAL_INSTALLED_MODULE\\)")
)

const (
	rexPairsHeader = 6
	rexPairsAssign = 8
	rexPairsFooter = 4
)

func (mk *MkFile) handleModule(scanner *myScanner, moduleType string) (*MkModule, error) {
	mod := MkModule{Location: scanner.lineNo, Type: moduleType, Variables: make(map[string]string)}
	includePath := ""
	for scanner.Scan() {
		line := scanner.Text()
		if rexEmpty.MatchString(line) {
			break
		}
		if m := rexAssign.FindStringSubmatchIndex(line); len(m) == rexPairsAssign {
			v := line[m[2]:m[3]]
			if line[m[4]:m[5]] == "+" {
				mod.Variables[v] = mod.Variables[v] + line[m[6]:m[7]]
			} else {
				mod.Variables[v] = line[m[6]:m[7]]
			}
		} else if m := rexFooter.FindStringSubmatchIndex(line); len(m) == rexPairsFooter {
			if includePath != "" {
				return nil, fmt.Errorf("%d: second include for module", scanner.lineNo)
			}
			includePath = strings.TrimSpace(line[m[2]:m[3]])
			if mod.Type == "" {
				mod.Type = includePath
			}
		} else if mod.Type != "" {
			mod.Extras = mod.Extras + 1
			continue
		} else if rexIgnore1.MatchString(line) {
			continue
		} else if rexIgnore2.MatchString(line) {
			continue
		} else {
			return nil, fmt.Errorf("%d: unexpected line:\n%s", scanner.lineNo, line)
		}
	}
	return &mod, scanner.Err()
}

func (mk *MkFile) ModulesByType(names []string) (sortedKeys []string, byType map[string][]string) {
	byType = make(map[string][]string)
	for _, name := range names {
		mod, ok := mk.Modules[name]
		if !ok {
			break
		}
		mt := mod.Type
		v, ok := byType[mt]
		if !ok {
			sortedKeys = append(sortedKeys, mt)
		}
		byType[mt] = append(v, name)
	}
	sort.Strings(sortedKeys)
	return
}

func (mk *MkFile) moduleKey(mod *MkModule) (string, error) {
	// Synthesize unique module name.
	name := mod.Variables["LOCAL_MODULE"]
	if name == "" {
		return "", fmt.Errorf("%d: the module above lacks LOCAL_MODULE assignment", mod.Location)
	}
	var buf strings.Builder
	writebuf := func(chunks ...string) {
		for _, s := range chunks {
			buf.WriteString(s)
		}
	}

	writebuf(name, "|class:", mod.Variables["LOCAL_MODULE_CLASS"])
	if mod.Variables["LOCAL_IS_HOST_MODULE"] == "true" {
		if v, ok := mod.Variables["LOCAL_MODULE_HOST_ARCH"]; ok {
			writebuf("|host_arch:", v)
		}
		if v, ok := mod.Variables["LOCAL_MODULE_HOST_CROSS_ARCH"]; ok {
			writebuf("|cross_arch:", v)
		}
	} else {
		if v, ok := mod.Variables["LOCAL_MODULE_TARGET_ARCH"]; ok {
			writebuf("|target_arch:", v)
		} else {
			writebuf("|target_arch:*")
		}
	}
	return buf.String(), nil
}

// ParseMkFile parses Android-TARGET.mk file generated by Android build
func ParseMkFile(source io.Reader) (*MkFile, error) {
	scanner := &myScanner{bufio.NewScanner(source), 0}
	buffer := make([]byte, 1000000000)
	scanner.Scanner.Buffer(buffer, len(buffer))
	mkFile := &MkFile{Modules: make(map[string]*MkModule)}

	for scanner.Scan() {
		line := scanner.Text()
		m := rexHeader.FindStringSubmatchIndex(line)
		if len(m) != rexPairsHeader {
			continue
		}
		moduleType := ""
		if m[4] >= 0 {
			moduleType = line[m[4]:m[5]]
		}
		mod, err := mkFile.handleModule(scanner, moduleType)
		if err != nil {
			return mkFile, err
		}
		name, err := mkFile.moduleKey(mod)
		if err != nil {
			return mkFile, err
		}
		if old, found := mkFile.Modules[name]; found {
			return mkFile, fmt.Errorf(":%d: module %s already found, diff: %s", old.Location, name, cmp.Diff(old, mod))
		}
		mkFile.Modules[name] = mod
	}
	return mkFile, scanner.Err()
}