package schema

import (
	"errors"
	"reflect"
	"strings"

	"git.gdulai.com/gdulai/simpleorm/util"
)

type OrderBy struct {
	Field     string
	Direction string
}

type Table struct {
	name        string
	typ         reflect.Type
	columns     []Column
	constraints []Constraint
}

func (t Table) Name() string {
	return t.name
}

func (t Table) Type() reflect.Type {
	return t.typ
}

func (t Table) Columns() []Column {
	return t.columns
}

func (t Table) Constraints() []Constraint {
	return t.constraints
}

func (t Table) GetDDL() (string, error) {
	var ddl strings.Builder
	ddl.WriteString("CREATE TABLE IF NOT EXISTS ")
	ddl.WriteString(t.name)
	ddl.WriteString(" (")
	for i, col := range t.columns {
		if i != 0 {
			ddl.WriteString(", ")
		}
		colDdl, err := col.GetDDL()
		if err != nil {
			return "", err
		}
		ddl.WriteString(colDdl)
	}
	for _, constr := range t.constraints {
		constrDdl, err := constr.GetDDL()
		if err != nil {
			return "", err
		}
		ddl.WriteString(", ")
		ddl.WriteString(constrDdl)
	}

	ddl.WriteString(");")
	return ddl.String(), nil
}

func (t Table) GetSelectDML() (string, error) {
	var dml strings.Builder
	dml.WriteString("SELECT ")

	for i, col := range t.columns {
		if i != 0 {
			dml.WriteString(", ")
		}
		colDml, err := col.GetSelectDML()
		if err != nil {
			return "", err
		}
		dml.WriteString(colDml)
	}

	dml.WriteString(" FROM ")
	dml.WriteString(t.name)
	return dml.String(), nil
}

func (t Table) GetCountDML() string {
	return "SELECT COUNT(*) FROM " + t.name
}

func (t Table) GetInsertDML(count int) (string, error) {
	var dml strings.Builder
	dml.WriteString("INSERT INTO ")
	dml.WriteString(util.CamelToSnake(t.typ.Name()))
	dml.WriteString(" (")

	columnsLen := len(t.columns)
	effectiveColumnsLen := 0
	for i, col := range t.columns {
		_, ok := col.Modifiers["pk"]
		if ok && t.IsPkAuto() {
			continue
		}

		colDml, err := col.GetInsertDML()
		if err != nil {
			return "", err
		}

		dml.WriteString(colDml)
		if i != columnsLen-1 {
			dml.WriteString(", ")
		}
		effectiveColumnsLen++
	}

	dml.WriteString(") VALUES")

	for i := range count {
		if i != 0 {
			dml.WriteString(", ")
		}
		for j := range effectiveColumnsLen {
			if j == 0 {
				dml.WriteString("(")
			}
			if j != effectiveColumnsLen-1 {
				dml.WriteString("?, ")
			} else {
				dml.WriteString("?)")
			}
		}
	}

	dml.WriteString(" RETURNING *")

	return dml.String(), nil
}

func (t Table) GetUpdateDML() (string, error) {
	var dml strings.Builder
	dml.WriteString("UPDATE  ")
	dml.WriteString(util.CamelToSnake(t.typ.Name()))
	dml.WriteString(" SET ")

	colLen := len(t.columns)
	var pkColumns []string
	// Colum names
	for i, col := range t.columns {
		modifiers := col.Modifiers

		_, ok := modifiers["pk"]
		if ok {
			pkColumns = append(pkColumns, col.Name)
			if t.IsPkAuto() {
				continue
			}
		}

		colDml, err := col.GetUpdateDML()
		if err != nil {
			return "", err
		}

		if i != colLen-1 {
			dml.WriteString(colDml)
			dml.WriteString(", ")
		} else {
			dml.WriteString(colDml)
			dml.WriteString(" ")
		}
	}

	dml.WriteString("WHERE ")

	for i, pkCol := range pkColumns {
		if i != 0 {
			dml.WriteString(" AND ")
		}
		dml.WriteString(pkCol)
		dml.WriteString(" = ?")
	}

	return dml.String(), nil
}

func (t Table) GetDeleteDML(count int) (string, error) {
	var dml strings.Builder
	dml.WriteString("DELETE FROM ")
	dml.WriteString(t.name)
	dml.WriteString(" WHERE ")

	for _, col := range t.columns {
		modifiers := col.Modifiers

		_, ok := modifiers["pk"]
		if ok {
			if count > 1 {
				dml.WriteString(col.Name)
				dml.WriteString(" IN (")
			} else {
				dml.WriteString(col.Name)
				dml.WriteString(" = ")
			}
		}
	}

	for i := range count {
		if i != 0 {
			dml.WriteString(", ")
		}
		dml.WriteString("?")
	}

	if count > 1 {
		dml.WriteString(")")
	}

	return dml.String(), nil
}

func (t Table) GetOrderByDML(ordering ...OrderBy) (string, error) {
	var dml strings.Builder
	dml.WriteString(" ORDER BY")
	for _, orderBy := range ordering {
		col, err := t.getColumnByField(orderBy.Field)
		if err != nil {
			return "", err
		}
		dml.WriteString(" ")
		dml.WriteString(col.Name)
		dml.WriteString(" ")
		dml.WriteString(orderBy.Direction)
	}
	return dml.String(), nil
}

func (t Table) getColumnByField(fieldName string) (Column, error) {
	for _, col := range t.columns {
		if col.FieldName == fieldName {
			return col, nil
		}
	}
	return Column{}, errors.New("No column for field " + fieldName + " in table " + t.name)
}

func (t Table) IsPkAuto() bool {
	for _, constr := range t.constraints {
		if constr.Type != "pk" {
			continue
		}

		return len(constr.Columns) == 1
	}
	return true
}