package cmd

import (
	"encoding/json"
	"fmt"
	"io"
	"os"
	"strings"

	"github.com/spf13/cobra"

	"github.com/sqlc-dev/sqlc/internal/engine/clickhouse"
	"github.com/sqlc-dev/sqlc/internal/engine/dolphin"
	"github.com/sqlc-dev/sqlc/internal/engine/duckdb"
	"github.com/sqlc-dev/sqlc/internal/engine/googlesql"
	"github.com/sqlc-dev/sqlc/internal/engine/mssql"
	"github.com/sqlc-dev/sqlc/internal/engine/postgresql"
	"github.com/sqlc-dev/sqlc/internal/engine/sqlite"
	"github.com/sqlc-dev/sqlc/internal/metadata"
	"github.com/sqlc-dev/sqlc/internal/source"
	"github.com/sqlc-dev/sqlc/internal/sql/ast"
)

// dialectParser is the subset of the engine parsers that the parse command
// needs: parsing SQL into statements and reporting the dialect's comment syntax
// (used to extract the sqlc query name and command).
type dialectParser interface {
	Parse(io.Reader) ([]ast.Statement, error)
	CommentSyntax() source.CommentSyntax
}

// parsedStatement is the JSON representation of a single parsed statement. The
// name and cmd are extracted from the sqlc query annotation (e.g.
// "-- name: GetAuthor :one") and are omitted when the statement has none.
type parsedStatement struct {
	Name string       `json:"name,omitempty"`
	Cmd  string       `json:"cmd,omitempty"`
	AST  *ast.RawStmt `json:"ast"`
}

func newParseCmd() *cobra.Command {
	cmd := &cobra.Command{
		Use:   "parse [file]",
		Short: "Parse SQL and output the AST as JSON",
		Long: `Parse SQL from a file or stdin and output the abstract syntax tree as JSON.

Each statement is reported with its sqlc query name and command (when the
statement carries a "-- name:" annotation) alongside the AST.

Examples:
  # Parse a SQL file with PostgreSQL dialect
  sqlc parse --dialect postgresql schema.sql

  # Parse from stdin with MySQL dialect
  echo "SELECT * FROM users" | sqlc parse --dialect mysql

  # Parse SQLite SQL
  sqlc parse --dialect sqlite queries.sql

  # Parse ClickHouse SQL
  sqlc parse --dialect clickhouse queries.sql

  # Parse GoogleSQL (BigQuery, Spanner)
  sqlc parse --dialect googlesql queries.sql

  # Parse SQL Server (T-SQL) SQL
  sqlc parse --dialect mssql queries.sql

  # Parse DuckDB SQL
  sqlc parse --dialect duckdb queries.sql`,
		Args: cobra.MaximumNArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			dialect, err := cmd.Flags().GetString("dialect")
			if err != nil {
				return err
			}
			if dialect == "" {
				return fmt.Errorf("--dialect flag is required (postgresql, mysql, sqlite, clickhouse, googlesql, mssql, or duckdb)")
			}

			// Determine input source
			var input io.Reader
			if len(args) == 1 {
				file, err := os.Open(args[0])
				if err != nil {
					return fmt.Errorf("failed to open file: %w", err)
				}
				defer file.Close()
				input = file
			} else {
				// Check if stdin has data
				stat, err := os.Stdin.Stat()
				if err != nil {
					return fmt.Errorf("failed to stat stdin: %w", err)
				}
				if (stat.Mode() & os.ModeCharDevice) != 0 {
					return fmt.Errorf("no input provided. Specify a file path or pipe SQL via stdin")
				}
				input = cmd.InOrStdin()
			}

			// Select the parser for the requested dialect
			var parser dialectParser
			switch dialect {
			case "postgresql", "postgres", "pg":
				parser = postgresql.NewParser()
			case "mysql":
				parser = dolphin.NewParser()
			case "sqlite":
				parser = sqlite.NewParser()
			case "clickhouse":
				parser = clickhouse.NewParser()
			case "googlesql":
				parser = googlesql.NewParser()
			case "mssql", "sqlserver":
				parser = mssql.NewParser()
			case "duckdb":
				parser = duckdb.NewParser()
			default:
				return fmt.Errorf("unsupported dialect: %s (use postgresql, mysql, sqlite, clickhouse, googlesql, mssql, or duckdb)", dialect)
			}

			// Read the full source so each statement's name and command can be
			// extracted from its annotation comment.
			src, err := io.ReadAll(input)
			if err != nil {
				return fmt.Errorf("failed to read input: %w", err)
			}

			stmts, err := parser.Parse(strings.NewReader(string(src)))
			if err != nil {
				return fmt.Errorf("parse error: %w", err)
			}

			commentSyntax := metadata.CommentSyntax(parser.CommentSyntax())

			// Output the AST as a single JSON document
			out := make([]parsedStatement, 0, len(stmts))
			for _, stmt := range stmts {
				ps := parsedStatement{AST: stmt.Raw}
				rawSQL, err := source.Pluck(string(src), stmt.Raw.StmtLocation, stmt.Raw.StmtLen)
				if err != nil {
					return fmt.Errorf("failed to read statement source: %w", err)
				}
				name, cmd, err := metadata.ParseQueryNameAndType(rawSQL, commentSyntax)
				if err != nil {
					return fmt.Errorf("failed to parse query annotation: %w", err)
				}
				ps.Name = name
				ps.Cmd = cmd
				out = append(out, ps)
			}

			stdout := cmd.OutOrStdout()
			encoder := json.NewEncoder(stdout)
			encoder.SetIndent("", "  ")
			if err := encoder.Encode(out); err != nil {
				return fmt.Errorf("failed to encode AST: %w", err)
			}

			return nil
		},
	}
	cmd.Flags().StringP("dialect", "d", "", "SQL dialect to use (postgresql, mysql, sqlite, clickhouse, googlesql, mssql, or duckdb)")
	return cmd
}