package postgres

import (
	"strings"

	"git.fsdpf.net/go/db/v2"
	"git.fsdpf.net/go/db/v2/dialect/postgres"
	"git.fsdpf.net/go/db/v2/internal/sb"
	"git.fsdpf.net/go/db/v2/schema"
	"git.fsdpf.net/go/db/v2/sqlgen"
)

type Postgres struct {
	db  *db.Database
	esg sqlgen.ExpressionSQLGenerator
}

var pgDefaultModifiers = []string{
	"Nullable", "Default", "Increment", "Comment",
}
var pgSerials = []string{
	"bigInteger", "integer", "smallInteger",
}

func (this Postgres) GetColumnListing(table string) ([]string, error) {
	cols := []string{}
	err := this.db.From(db.S("information_schema").Table("columns")).Where(
		db.C("table_name").Eq(table),
		db.C("table_schema").Eq(db.L("current_database()")),
	).Pluck(&cols, "column_name")
	return cols, err
}

func (this Postgres) TableExists(table string) (bool, error) {
	result, err := this.db.From(db.S("information_schema").Table("tables")).Where(db.Ex{
		"table_name":   table,
		"table_schema": db.L("current_database()"),
	}).Count()
	return result > 0, err
}

func (this Postgres) CompileCreate(bp *schema.Blueprint) []string {
	temporary := db.L("CREATE")
	if bp.IsTemporary() {
		temporary = db.L("CREATE TEMPORARY")
	}
	columns := strings.Join(this.getAddedColumns(bp), ",\n")
	sql := this.GenerateSQL("? TABLE ? (\n?\n)", temporary, db.T(bp.GetTable()), db.L(columns))
	return []string{sql}
}

func (this Postgres) CompileAdd(bp *schema.Blueprint) []string {
	columns := strings.Join(schema.PrefixArray("ADD COLUMN", this.getAddedColumns(bp)), ",\n")
	sql := this.GenerateSQL("ALTER TABLE ?\n?", db.T(bp.GetTable()), db.L(columns))
	return []string{sql}
}

func (this Postgres) CompileChange(bp *schema.Blueprint) []string {
	columns := strings.Join(schema.PrefixArray("ALTER COLUMN", this.getChangedColumns(bp)), ",\n")
	sql := this.GenerateSQL("ALTER TABLE ?\n?", db.T(bp.GetTable()), db.L(columns))
	return []string{sql}
}

func (this Postgres) CompileDropColumn(bp *schema.Blueprint) []string {
	columns := []string{}
	for _, item := range bp.GetCommands() {
		if item.Type != "dropColumn" {
			continue
		}
		for _, col := range item.Columns {
			columns = append(columns, this.GenerateSQL("DROP COLUMN ?", db.C(col)))
		}
	}
	sql := this.GenerateSQL("ALTER TABLE ?\n?", db.T(bp.GetTable()), db.L(strings.Join(columns, ",\n")))
	return []string{sql}
}

func (this Postgres) CompileDrop(bp *schema.Blueprint) []string {
	return []string{this.GenerateSQL("DROP TABLE ?", db.T(bp.GetTable()))}
}

func (this Postgres) CompileDropIfExists(bp *schema.Blueprint) []string {
	return []string{this.GenerateSQL("DROP TABLE IF EXISTS ?", db.T(bp.GetTable()))}
}

func (this Postgres) CompileRename(bp *schema.Blueprint) []string {
	toName := ""
	commands := bp.GetCommands()
	if len(commands) == 0 {
		panic("new table undefined")
	}
	toName = bp.GetCommands()[0].To
	if toName == "" {
		panic("new table undefined")
	}
	return []string{this.GenerateSQL("ALTER TABLE ? RENAME TO ?", db.T(bp.GetTable()), db.T(toName))}
}

func (this Postgres) addModifiers(sql string, bp *schema.Blueprint, column *schema.ColumnDefinition) string {
	for _, modifier := range pgDefaultModifiers {
		sql += this.GetColumnModifier(modifier, bp, column)
	}
	return sql
}

func (this Postgres) GetColumnType(column *schema.ColumnDefinition) string {
	switch column.Type {
	case "char":
		return this.GenerateSQL("char(?)", column.Length)
	case "string":
		return this.GenerateSQL("varchar(?)", column.Length)
	case "text":
		return "text"
	case "integer":
		return "integer"
	case "bigInteger":
		return "bigint"
	case "smallInteger":
		return "smallint"
	case "decimal":
		return this.GenerateSQL("numeric(?,?)", column.Total, column.Places)
	case "boolean":
		return "boolean"
	case "enum":
		return this.GenerateSQL("varchar(?)", column.Length) // PostgreSQL uses custom types or check constraints
	case "json":
		return "json"
	case "binary":
		return "bytea"
	case "datetime":
		return "timestamp without time zone"
	case "timestamp":
		return "timestamp with time zone"
	case "date":
		return "date"
	case "time":
		return "time"
	case "year":
		return "integer"
	case "uuid":
		return "uuid"
	}
	panic("Unsupported data type: " + column.Type)
}

func (this Postgres) GetColumnModifier(modifier string, bp *schema.Blueprint, column *schema.ColumnDefinition) string {
	switch modifier {
	case "Nullable":
		if column.IsNullable() {
			return " NULL"
		}
		return " NOT NULL"
	case "Default":
		v := column.GetDefault()
		if v == nil {
			if column.IsUseCurrent() {
				return " DEFAULT CURRENT_TIMESTAMP"
			}
			return ""
		}
		if column.IsUseCurrent() {
			return this.GenerateSQL(" DEFAULT CURRENT_TIMESTAMP ?", v)
		}
		return this.GenerateSQL(" DEFAULT ?", v)
	case "Increment":
		if column.IsAutoIncrement() {
			switch column.Type {
			case "integer":
				return " SERIAL PRIMARY KEY"
			case "bigInteger":
				return " BIGSERIAL PRIMARY KEY"
			case "smallInteger":
				return " SMALLSERIAL PRIMARY KEY"
			}
		}
	case "Comment":
		// PostgreSQL handles comments separately via COMMENT ON
		return ""
	}
	return ""
}

func (this Postgres) getAddedColumns(bp *schema.Blueprint) (columns []string) {
	for _, column := range bp.GetAddedColumns() {
		sql := this.GenerateSQL("? ?", db.C(column.Name), db.L(this.GetColumnType(column)))
		columns = append(columns, this.addModifiers(sql, bp, column))
	}
	return
}

func (this Postgres) getChangedColumns(bp *schema.Blueprint) (columns []string) {
	for _, column := range bp.GetChangedColumns() {
		sql := this.GenerateSQL("? TYPE ?", db.C(column.Name), db.L(this.GetColumnType(column)))
		columns = append(columns, this.addModifiers(sql, bp, column))
	}
	return
}

func (this Postgres) GenerateSQL(sql string, args ...any) string {
	sb := sb.NewSQLBuilder(false)
	this.esg.Generate(sb, db.L(sql, args...))
	result, _, _ := sb.ToSQL()
	return result
}

func init() {
	schema.RegisterDialect("postgres", func(db *db.Database) schema.Schema {
		return &Postgres{
			db:  db,
			esg: sqlgen.NewExpressionSQLGenerator("postgres", postgres.DialectOptions()),
		}
	})
}