package build

import (
	"bytes"
	"fmt"
	"go/ast"
	"go/parser"
	"go/token"
	"os"
	"path/filepath"
	"sort"
	"strings"
)

const (
	registryFileName  = "registry.gen.go"
	generatedMark     = "Code generated by summer make"
)

type identScanKind int

const (
	scanStructs identScanKind = iota
	scanMigrationFuncs
	scanCommandFuncs
	scanJobFuncs
	scanAdminFuncs
)

type registryRef struct {
	Package string
	Ident   string
	SortKey string
}

type registryData struct {
	Package          string
	Module           string
	Imports          []string
	Models           []registryRef
	Migrations       []registryRef
	Commands         []registryRef
	Jobs             []registryRef
	AdminControllers []registryRef
}

func emptyRegistry(pkg, module string) registryData {
	data := registryData{Package: pkg, Module: module}
	data.prepare()
	return data
}

func (d *registryData) prepare() {
	d.Imports = uniqueLeafImports(d.Module, d.Models, d.Migrations, d.Commands, d.Jobs, d.AdminControllers)
}

func uniqueLeafImports(module string, groups ...[]registryRef) []string {
	if module == "" {
		return nil
	}
	seen := make(map[string]struct{})
	var imports []string
	for _, group := range groups {
		for _, ref := range group {
			if ref.Package == "" {
				continue
			}
			path := module + "/" + ref.Package
			if _, ok := seen[path]; ok {
				continue
			}
			seen[path] = struct{}{}
			imports = append(imports, path)
		}
	}
	sort.Strings(imports)
	return imports
}

func refreshRegistry(pluginDir string) error {
	pkg, err := packageNameOf(filepath.Join(pluginDir, "plugin.go"))
	if err != nil {
		return err
	}
	module, err := readModulePath(filepath.Join(pluginDir, "go.mod"))
	if err != nil {
		return err
	}
	data := registryData{Package: pkg, Module: module}
	if data.Models, err = scanGeneratedIdents(filepath.Join(pluginDir, "models"), "models", scanStructs); err != nil {
		return err
	}
	if data.Migrations, err = scanGeneratedIdents(filepath.Join(pluginDir, "updates"), "updates", scanMigrationFuncs); err != nil {
		return err
	}
	if data.Commands, err = scanGeneratedIdents(filepath.Join(pluginDir, "console"), "console", scanCommandFuncs); err != nil {
		return err
	}
	if data.Jobs, err = scanGeneratedIdents(filepath.Join(pluginDir, "jobs"), "jobs", scanJobFuncs); err != nil {
		return err
	}
	if data.AdminControllers, err = scanGeneratedIdents(filepath.Join(pluginDir, "controllers"), "controllers", scanAdminFuncs); err != nil {
		return err
	}
	sortRefs(data.Models)
	sortRefs(data.Migrations)
	sortRefs(data.Commands)
	sortRefs(data.Jobs)
	sortRefs(data.AdminControllers)
	return writeRegistry(pluginDir, data)
}

func packageNameOf(path string) (string, error) {
	fset := token.NewFileSet()
	file, err := parser.ParseFile(fset, path, nil, parser.PackageClauseOnly)
	if err != nil {
		return "", fmt.Errorf("build: parse %s: %w", path, err)
	}
	if file.Name == nil || file.Name.Name == "" {
		return "", fmt.Errorf("build: %s has no package name", path)
	}
	return file.Name.Name, nil
}

func scanGeneratedIdents(dir, pkg string, kind identScanKind) ([]registryRef, error) {
	entries, err := os.ReadDir(dir)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, nil
		}
		return nil, fmt.Errorf("build: read %s: %w", dir, err)
	}
	fset := token.NewFileSet()
	var refs []registryRef
	for _, entry := range entries {
		name := entry.Name()
		if entry.IsDir() || !strings.HasSuffix(name, ".go") || strings.HasSuffix(name, "_test.go") || name == "doc.go" {
			continue
		}
		path := filepath.Join(dir, name)
		file, err := parser.ParseFile(fset, path, nil, parser.ParseComments)
		if err != nil {
			return nil, fmt.Errorf("build: parse %s: %w", path, err)
		}
		if !isGeneratedFile(file) {
			continue
		}
		switch kind {
		case scanStructs:
			refs = append(refs, structRefs(pkg, name, file)...)
		default:
			want := resultTypeFor(kind)
			refs = append(refs, funcRefs(pkg, name, file, want)...)
		}
	}
	return refs, nil
}

func resultTypeFor(kind identScanKind) string {
	switch kind {
	case scanMigrationFuncs:
		return "gormigrate.Migration"
	case scanCommandFuncs:
		return "bonfire.Command"
	case scanJobFuncs:
		return "pact.Job"
	case scanAdminFuncs:
		return "pact.AdminController"
	default:
		return ""
	}
}

func isGeneratedFile(file *ast.File) bool {
	for _, cg := range file.Comments {
		for _, c := range cg.List {
			if strings.Contains(c.Text, generatedMark) {
				return true
			}
		}
	}
	return false
}

func structRefs(pkg, filename string, file *ast.File) []registryRef {
	var refs []registryRef
	for _, decl := range file.Decls {
		gd, ok := decl.(*ast.GenDecl)
		if !ok {
			continue
		}
		for _, spec := range gd.Specs {
			ts, ok := spec.(*ast.TypeSpec)
			if !ok || ts.Name == nil || !ts.Name.IsExported() {
				continue
			}
			if _, ok := ts.Type.(*ast.StructType); !ok {
				continue
			}
			refs = append(refs, registryRef{Package: pkg, Ident: ts.Name.Name, SortKey: ts.Name.Name})
		}
	}
	_ = filename
	return refs
}

func funcRefs(pkg, filename string, file *ast.File, want string) []registryRef {
	var refs []registryRef
	for _, decl := range file.Decls {
		fn, ok := decl.(*ast.FuncDecl)
		if !ok || fn.Recv != nil || fn.Name == nil || !fn.Name.IsExported() || fn.Type == nil {
			continue
		}
		if fn.Type.Params != nil && len(fn.Type.Params.List) > 0 {
			continue
		}
		if fn.Type.Results == nil || len(fn.Type.Results.List) != 1 {
			continue
		}
		if astTypeName(fn.Type.Results.List[0].Type) != want {
			continue
		}
		refs = append(refs, registryRef{
			Package: pkg,
			Ident:   fn.Name.Name,
			SortKey: strings.TrimSuffix(filename, ".go"),
		})
	}
	return refs
}

func astTypeName(expr ast.Expr) string {
	switch t := expr.(type) {
	case *ast.StarExpr:
		return astTypeName(t.X)
	case *ast.SelectorExpr:
		if id, ok := t.X.(*ast.Ident); ok && t.Sel != nil {
			return id.Name + "." + t.Sel.Name
		}
	case *ast.Ident:
		return t.Name
	}
	return ""
}

func sortRefs(refs []registryRef) {
	sort.Slice(refs, func(i, j int) bool {
		a, b := refs[i].SortKey, refs[j].SortKey
		if a == "" {
			a = refs[i].Ident
		}
		if b == "" {
			b = refs[j].Ident
		}
		if a == b {
			return refs[i].Ident < refs[j].Ident
		}
		return a < b
	})
}

func writeRegistry(pluginDir string, data registryData) error {
	data.prepare()
	src, err := renderStub("registry.go", data)
	if err != nil {
		return err
	}
	path := filepath.Join(pluginDir, registryFileName)
	existing, err := os.ReadFile(path)
	if err == nil && bytes.Equal(existing, src) {
		return nil
	}
	if err != nil && !os.IsNotExist(err) {
		return fmt.Errorf("build: read %s: %w", path, err)
	}
	tmp, err := os.CreateTemp(pluginDir, registryFileName+".*")
	if err != nil {
		return fmt.Errorf("build: create %s temp: %w", registryFileName, err)
	}
	tmpName := tmp.Name()
	if _, err := tmp.Write(src); err != nil {
		tmp.Close()
		os.Remove(tmpName)
		return fmt.Errorf("build: write %s temp: %w", registryFileName, err)
	}
	if err := tmp.Close(); err != nil {
		os.Remove(tmpName)
		return fmt.Errorf("build: close %s temp: %w", registryFileName, err)
	}
	if err := os.Rename(tmpName, path); err != nil {
		os.Remove(tmpName)
		return fmt.Errorf("build: rename %s: %w", registryFileName, err)
	}
	return nil
}