// Copyright 2019 The Xorm Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package cmd

import (
	"bytes"
	"errors"
	"html/template"
	"io/ioutil"
	"os"
	"path/filepath"
	"strings"

	"xorm.io/reverse/language"

	"gitea.com/lunny/log"
	_ "github.com/denisenkom/go-mssqldb"
	_ "github.com/go-sql-driver/mysql"
	"github.com/gobwas/glob"
	_ "github.com/lib/pq"
	_ "github.com/mattn/go-sqlite3"
	"gopkg.in/yaml.v2"
	"xorm.io/core"
	"xorm.io/xorm"
)

func reverse(rFile string) error {
	f, err := os.Open(rFile)
	if err != nil {
		return err
	}
	defer f.Close()

	var cfg ReverseConfig
	err = yaml.NewDecoder(f).Decode(&cfg)
	if err != nil {
		return err
	}
	for _, target := range cfg.Targets {
		if err := runReverse(&cfg.Source, &target); err != nil {
			return err
		}
	}

	return nil
}

type ReverseSource struct {
	Database string `yaml:"database"`
	ConnStr  string `yaml:"conn_str"`
}

// ReverseTarget represents a reverse target
type ReverseTarget struct {
	Type          string   `yaml:"type"`
	IncludeTables []string `yaml:"include_tables"`
	ExcludeTables []string `yaml:"exclude_tables"`
	TableMapper   string   `yaml:"table_mapper"`
	ColumnMapper  string   `yaml:"column_mapper"`
	TemplatePath  string   `yaml:"template_path"`
	Template      string   `yaml:"template"`
	MultipleFiles bool     `yaml:"multiple_files"`
	OutputDir     string   `yaml:"output_dir"`
	TablePrefix   string   `yaml:"table_prefix"`
	Language      string   `yaml:"language"`

	Funcs     map[string]string `yaml:"funcs"`
	Formatter string            `yaml:"formatter"`
	Importter string            `yaml:"importter"`
	ExtName   string            `yaml:"ext_name"`
}

// ReverseConfig represents a reverse configuration
type ReverseConfig struct {
	Kind    string          `yaml:"kind"`
	Name    string          `yaml:"name"`
	Source  ReverseSource   `yaml:"source"`
	Targets []ReverseTarget `yaml:"targets"`
}

var (
	formatters   = map[string]func(string) (string, error){}
	importters   = map[string]func([]*core.Table) []string{}
	defaultFuncs = template.FuncMap{
		"UnTitle": unTitle,
		"Upper":   upTitle,
	}
)

func unTitle(src string) string {
	if src == "" {
		return ""
	}

	if len(src) == 1 {
		return strings.ToLower(string(src[0]))
	} else {
		return strings.ToLower(string(src[0])) + src[1:]
	}
}

func upTitle(src string) string {
	if src == "" {
		return ""
	}

	return strings.ToUpper(src)
}

func filterTables(tables []*core.Table, target *ReverseTarget) []*core.Table {
	var res = make([]*core.Table, 0, len(tables))
	for _, tb := range tables {
		var remove bool
		for _, exclude := range target.ExcludeTables {
			s, _ := glob.Compile(exclude)
			remove = s.Match(tb.Name)
			if remove {
				break
			}
		}
		if remove {
			continue
		}
		if len(target.IncludeTables) == 0 {
			res = append(res, tb)
			continue
		}

		var keep bool
		for _, include := range target.IncludeTables {
			s, _ := glob.Compile(include)
			keep = s.Match(tb.Name)
			if keep {
				break
			}
		}
		if keep {
			res = append(res, tb)
		}
	}
	return res
}

func newFuncs() template.FuncMap {
	var m = make(template.FuncMap)
	for k, v := range defaultFuncs {
		m[k] = v
	}
	return m
}

func runReverse(source *ReverseSource, target *ReverseTarget) error {
	orm, err := xorm.NewEngine(source.Database, source.ConnStr)
	if err != nil {
		return err
	}

	tables, err := orm.DBMetas()
	if err != nil {
		return err
	}

	// filter tables according includes and excludes
	tables = filterTables(tables, target)

	// load configuration from language
	lang := language.GetLanguage(target.Language)
	funcs := newFuncs()
	formatter := formatters[target.Formatter]
	importter := importters[target.Importter]

	// load template
	var bs []byte
	if target.Template != "" {
		bs = []byte(target.Template)
	} else if target.TemplatePath != "" {
		bs, err = ioutil.ReadFile(target.TemplatePath)
		if err != nil {
			return err
		}
	}

	if lang != nil {
		if bs == nil {
			bs = []byte(lang.Template)
		}
		for k, v := range lang.Funcs {
			funcs[k] = v
		}
		if formatter == nil {
			formatter = lang.Formatter
		}
		if importter == nil {
			importter = lang.Importter
		}
		target.ExtName = lang.ExtName
	}
	if !strings.HasPrefix(target.ExtName, ".") {
		target.ExtName = "." + target.ExtName
	}

	var tableMapper, colMapper core.IMapper
	switch target.TableMapper {
	case "gonic":
		tableMapper = core.LintGonicMapper
	case "same":
		tableMapper = core.SameMapper{}
	default:
		tableMapper = core.SnakeMapper{}
	}
	switch target.ColumnMapper {
	case "gonic":
		colMapper = core.LintGonicMapper
	case "same":
		colMapper = core.SameMapper{}
	default:
		colMapper = core.SnakeMapper{}
	}
	funcs["TableMapper"] = tableMapper.Table2Obj
	funcs["ColumnMapper"] = colMapper.Table2Obj

	if bs == nil {
		return errors.New("You have to indicate template / template path or a language")
	}

	t := template.New("reverse")
	t.Funcs(funcs)

	tmpl, err := t.Parse(string(bs))
	if err != nil {
		return err
	}

	for _, table := range tables {
		if target.TablePrefix != "" {
			table.Name = strings.TrimPrefix(table.Name, target.TablePrefix)
		}
		for _, col := range table.Columns() {
			col.FieldName = colMapper.Table2Obj(col.Name)
		}
	}

	err = os.MkdirAll(target.OutputDir, os.ModePerm)
	if err != nil {
		return err
	}

	var w *os.File
	if !target.MultipleFiles {
		w, err = os.Create(filepath.Join(target.OutputDir, "models"+target.ExtName))
		if err != nil {
			return err
		}
		defer w.Close()

		imports := importter(tables)

		newbytes := bytes.NewBufferString("")
		err = tmpl.Execute(newbytes, map[string]interface{}{
			"Tables":  tables,
			"Imports": imports,
		})
		if err != nil {
			return err
		}

		tplcontent, err := ioutil.ReadAll(newbytes)
		if err != nil {
			return err
		}
		var source string
		if formatter != nil {
			source, err = formatter(string(tplcontent))
			if err != nil {
				log.Warnf("%v", err)
				source = string(tplcontent)
			}
		} else {
			source = string(tplcontent)
		}

		w.WriteString(source)
		w.Close()
	} else {
		for _, table := range tables {
			// imports
			tbs := []*core.Table{table}
			imports := importter(tbs)

			w, err := os.Create(filepath.Join(target.OutputDir, table.Name+target.ExtName))
			if err != nil {
				return err
			}
			defer w.Close()

			newbytes := bytes.NewBufferString("")
			err = tmpl.Execute(newbytes, map[string]interface{}{
				"Tables":  tbs,
				"Imports": imports,
			})
			if err != nil {
				return err
			}

			tplcontent, err := ioutil.ReadAll(newbytes)
			if err != nil {
				return err
			}
			var source string
			if formatter != nil {
				source, err = formatter(string(tplcontent))
				if err != nil {
					log.Warnf("%v", err)
					source = string(tplcontent)
				}
			} else {
				source = string(tplcontent)
			}

			w.WriteString(source)
			w.Close()
		}
	}

	return nil
}