package generator

import (
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"path/filepath"
	"strings"

	"go-common/app/tool/gengo/namer"
	"go-common/app/tool/gengo/types"

	"golang.org/x/tools/imports"

	"github.com/golang/glog"
)

func errs2strings(errors []error) []string {
	strs := make([]string, len(errors))
	for i := range errors {
		strs[i] = errors[i].Error()
	}
	return strs
}

// ExecutePackages runs the generators for every package in 'packages'. 'outDir'
// is the base directory in which to place all the generated packages; it
// should be a physical path on disk, not an import path. e.g.:
// /path/to/home/path/to/gopath/src/
// Each package has its import path already, this will be appended to 'outDir'.
func (c *Context) ExecutePackages(outDir string, packages Packages) error {
	var errors []error
	for _, p := range packages {
		if err := c.ExecutePackage(outDir, p); err != nil {
			errors = append(errors, err)
		}
	}
	if len(errors) > 0 {
		return fmt.Errorf("some packages had errors:\n%v\n", strings.Join(errs2strings(errors), "\n"))
	}
	return nil
}

// DefaultFileType is
type DefaultFileType struct {
	Format   func([]byte) ([]byte, error)
	Assemble func(io.Writer, *File)
}

// AssembleFile is
func (ft DefaultFileType) AssembleFile(f *File, pathname string) error {
	glog.V(2).Infof("Assembling file %q", pathname)
	destFile, err := os.Create(pathname)
	if err != nil {
		return err
	}
	defer destFile.Close()

	b := &bytes.Buffer{}
	et := NewErrorTracker(b)
	ft.Assemble(et, f)
	if et.Error() != nil {
		return et.Error()
	}
	if formatted, err := ft.Format(b.Bytes()); err != nil {
		err = fmt.Errorf("unable to format file %q (%v)", pathname, err)
		// Write the file anyway, so they can see what's going wrong and fix the generator.
		if _, err2 := destFile.Write(b.Bytes()); err2 != nil {
			return err2
		}
		return err
	} else {
		_, err = destFile.Write(formatted)
		return err
	}
}

// VerifyFile is
func (ft DefaultFileType) VerifyFile(f *File, pathname string) error {
	glog.V(2).Infof("Verifying file %q", pathname)
	friendlyName := filepath.Join(f.PackageName, f.Name)
	b := &bytes.Buffer{}
	et := NewErrorTracker(b)
	ft.Assemble(et, f)
	if et.Error() != nil {
		return et.Error()
	}
	formatted, err := ft.Format(b.Bytes())
	if err != nil {
		return fmt.Errorf("unable to format the output for %q: %v", friendlyName, err)
	}
	existing, err := ioutil.ReadFile(pathname)
	if err != nil {
		return fmt.Errorf("unable to read file %q for comparison: %v", friendlyName, err)
	}
	if bytes.Compare(formatted, existing) == 0 {
		return nil
	}
	// Be nice and find the first place where they differ
	i := 0
	for i < len(formatted) && i < len(existing) && formatted[i] == existing[i] {
		i++
	}
	eDiff, fDiff := existing[i:], formatted[i:]
	if len(eDiff) > 100 {
		eDiff = eDiff[:100]
	}
	if len(fDiff) > 100 {
		fDiff = fDiff[:100]
	}
	return fmt.Errorf("output for %q differs; first existing/expected diff: \n  %q\n  %q", friendlyName, string(eDiff), string(fDiff))
}

func assembleGolangFile(w io.Writer, f *File) {
	w.Write(f.Header)
	fmt.Fprintf(w, "package %v\n\n", f.PackageName)

	if len(f.Imports) > 0 {
		fmt.Fprint(w, "import (\n")
		for i := range f.Imports {
			if strings.Contains(i, "\"") {
				// they included quotes, or are using the
				// `name "path/to/pkg"` format.
				fmt.Fprintf(w, "\t%s\n", i)
			} else {
				fmt.Fprintf(w, "\t%q\n", i)
			}
		}
		fmt.Fprint(w, ")\n\n")
	}

	if f.Vars.Len() > 0 {
		fmt.Fprint(w, "var (\n")
		w.Write(f.Vars.Bytes())
		fmt.Fprint(w, ")\n\n")
	}

	if f.Consts.Len() > 0 {
		fmt.Fprint(w, "const (\n")
		w.Write(f.Consts.Bytes())
		fmt.Fprint(w, ")\n\n")
	}

	w.Write(f.Body.Bytes())
}

func importsWrapper(src []byte) ([]byte, error) {
	return imports.Process("", src, nil)
}

// NewGolangFile is
func NewGolangFile() *DefaultFileType {
	return &DefaultFileType{
		Format:   importsWrapper,
		Assemble: assembleGolangFile,
	}
}

// format should be one line only, and not end with \n.
func addIndentHeaderComment(b *bytes.Buffer, format string, args ...interface{}) {
	if b.Len() > 0 {
		fmt.Fprintf(b, "\n// "+format+"\n", args...)
	} else {
		fmt.Fprintf(b, "// "+format+"\n", args...)
	}
}

func (c *Context) filteredBy(f func(*Context, *types.Type) bool) *Context {
	c2 := *c
	c2.Order = []*types.Type{}
	for _, t := range c.Order {
		if f(c, t) {
			c2.Order = append(c2.Order, t)
		}
	}
	return &c2
}

// make a new context; inheret c.Namers, but add on 'namers'. In case of a name
// collision, the namer in 'namers' wins.
func (c *Context) addNameSystems(namers namer.NameSystems) *Context {
	if namers == nil {
		return c
	}
	c2 := *c
	// Copy the existing name systems so we don't corrupt a parent context
	c2.Namers = namer.NameSystems{}
	for k, v := range c.Namers {
		c2.Namers[k] = v
	}

	for name, namer := range namers {
		c2.Namers[name] = namer
	}
	return &c2
}

// ExecutePackage executes a single package. 'outDir' is the base directory in
// which to place the package; it should be a physical path on disk, not an
// import path. e.g.: '/path/to/home/path/to/gopath/src/' The package knows its
// import path already, this will be appended to 'outDir'.
func (c *Context) ExecutePackage(outDir string, p Package) error {
	path := filepath.Join(outDir, p.Path())
	glog.V(2).Infof("Processing package %q, disk location %q", p.Name(), path)
	// Filter out any types the *package* doesn't care about.
	packageContext := c.filteredBy(p.Filter)
	os.MkdirAll(path, 0755)
	files := map[string]*File{}
	for _, g := range p.Generators(packageContext) {
		// Filter out types the *generator* doesn't care about.
		genContext := packageContext.filteredBy(g.Filter)
		// Now add any extra name systems defined by this generator
		genContext = genContext.addNameSystems(g.Namers(genContext))

		fileType := g.FileType()
		if len(fileType) == 0 {
			return fmt.Errorf("generator %q must specify a file type", g.Name())
		}
		f := files[g.Filename()]
		if f == nil {
			// This is the first generator to reference this file, so start it.
			f = &File{
				Name:        g.Filename(),
				FileType:    fileType,
				PackageName: p.Name(),
				Header:      p.Header(g.Filename()),
				Imports:     map[string]struct{}{},
			}
			files[f.Name] = f
		} else {
			if f.FileType != g.FileType() {
				return fmt.Errorf("file %q already has type %q, but generator %q wants to use type %q", f.Name, f.FileType, g.Name(), g.FileType())
			}
		}

		if vars := g.PackageVars(genContext); len(vars) > 0 {
			addIndentHeaderComment(&f.Vars, "Package-wide variables from generator %q.", g.Name())
			for _, v := range vars {
				if _, err := fmt.Fprintf(&f.Vars, "%s\n", v); err != nil {
					return err
				}
			}
		}
		if consts := g.PackageConsts(genContext); len(consts) > 0 {
			addIndentHeaderComment(&f.Consts, "Package-wide consts from generator %q.", g.Name())
			for _, v := range consts {
				if _, err := fmt.Fprintf(&f.Consts, "%s\n", v); err != nil {
					return err
				}
			}
		}
		if err := genContext.executeBody(&f.Body, g); err != nil {
			return err
		}
		if imports := g.Imports(genContext); len(imports) > 0 {
			for _, i := range imports {
				f.Imports[i] = struct{}{}
			}
		}
	}

	var errors []error
	for _, f := range files {
		finalPath := filepath.Join(path, f.Name)
		assembler, ok := c.FileTypes[f.FileType]
		if !ok {
			return fmt.Errorf("the file type %q registered for file %q does not exist in the context", f.FileType, f.Name)
		}
		var err error
		if c.Verify {
			err = assembler.VerifyFile(f, finalPath)
		} else {
			err = assembler.AssembleFile(f, finalPath)
		}
		if err != nil {
			errors = append(errors, err)
		}
	}
	if len(errors) > 0 {
		return fmt.Errorf("errors in package %q:\n%v", p.Path(), strings.Join(errs2strings(errors), "\n"))
	}
	return nil
}

func (c *Context) executeBody(w io.Writer, generator Generator) error {
	et := NewErrorTracker(w)
	if err := generator.Init(c, et); err != nil {
		return err
	}
	for _, t := range c.Order {
		if err := generator.GenerateType(c, t, et); err != nil {
			return err
		}
	}
	if err := generator.Finalize(c, et); err != nil {
		return err
	}
	return et.Error()
}