package data

import (
	"context"
	"errors"
	"fmt"
	"log/slog"
	"time"

	"git.runcible.io/learning/pulley/internal/database"
	"git.runcible.io/learning/pulley/internal/validator"
	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgconn"
)

// MUST export fields to serialize them

type Movie struct {
	ID        int64     `json:"id"`
	CreatedAt time.Time `json:"-"` // omits always
	Title     string    `json:"title"`
	Year      int32     `json:"year,omitzero"`
	// Runtime   int32     `json:"runtime,omitzero"`
	// Use the Runtime type instead of int32. Note that the omitzero directive will
	// still work on this: if the Runtime field has the underlying value 0, then it will
	// be considered zero and omitted -- and the MarshalJSON() method we just made
	// won't be called at all.
	// VSCode will complain though about reflection issue
	Runtime Runtime  `json:"runtime,omitzero"`
	Genres  []string `json:"genres,omitzero"`
	Version int32    `json:"version"`
}

type MovieModel struct {
	db     database.PgxIface
	logger *slog.Logger
}

// So in regards to pulling the queries out into constants. I think it makes sense
// in a world where the query gets really gnarly, but here it ends up violating code locality
// and honestly doesn't provide that much utility in pgmock, because a regex is probably a better
// fit anyways for testing and mocks.

// If you the whitespace becomes a problem pgxmocks should use a real regex
// or a strings.Join(strings.Fields(q), " ") helper function could be used to normalizes
// all the sql strings. Postgres doesn't care about whitespace though.

const InsertMovieQuery = `
	INSERT INTO movies (title, year, runtime, genres)
	VALUES ($1, $2, $3, $4)
	RETURNING id, created_at, version`

func (m MovieModel) Insert(ctx context.Context, movie *Movie) error {

	args := []any{movie.Title, movie.Year, movie.Runtime, movie.Genres}

	row := m.db.QueryRow(ctx, InsertMovieQuery, args...)
	// Insert is mutating the Movie struct
	err := row.Scan(&movie.ID, &movie.CreatedAt, &movie.Version)
	return err
}

const GetMovieQuery = `
	SELECT id, created_at, title, year, runtime, genres, version
	FROM movies
	WHERE id = $1`

func (m MovieModel) Get(ctx context.Context, id int64) (*Movie, error) {
	// safety validation
	if id < 1 {
		return nil, ErrRecordNotFound
	}

	// Mimicking a long running query. FYI since this changes the number of returned
	// fields, so I implmented the throwaway variable to take care of that
	// query := `
	// 	SELECT pg_sleep(8), id, created_at, title, year, runtime, genres, version
	// 	FROM movies
	// 	WHERE id = $1
	// `

	var movie Movie

	err := m.db.QueryRow(ctx, GetMovieQuery, id).Scan(
		// &[]byte{}, // throwaway the pg_sleep value
		&movie.ID,
		&movie.CreatedAt,
		&movie.Title,
		&movie.Year,
		&movie.Runtime,
		&movie.Genres,
		&movie.Version,
	)
	if err != nil {
		switch {
		case errors.Is(err, pgx.ErrNoRows):
			return nil, ErrRecordNotFound
		default:
			return nil, err
		}
	}

	return &movie, nil
}

const UpdateMovieQuery = `
	UPDATE movies
	SET title = $1, year = $2, runtime = $3, genres = $4, version = version + 1
	WHERE id = $5 and version = $6
	RETURNING version`

func (m MovieModel) Update(ctx context.Context, movie *Movie) error {
	// Using version here as an optimistic lock. Look up optimistic vs pessimistic locking
	// https://stackoverflow.com/questions/129329/optimistic-vs-pessimistic-locking/129397#129397

	// version incrementing with an integer is cheap. Don't try with a last_updated timestamp...that could
	// cause issues. If you don't want version to be guessable then a UUID generated by the DB is suitable.
	// Example: SET ... version = uuid_generate_v4()

	args := []any{
		movie.Title,
		movie.Year,
		movie.Runtime,
		movie.Genres,
		movie.ID,
		movie.Version,
	}

	// Will not return any rows if the version number has already changed.
	err := m.db.QueryRow(ctx, UpdateMovieQuery, args...).Scan(&movie.Version)
	if err != nil {
		switch {
		case errors.Is(err, pgx.ErrNoRows):
			return ErrEditConflict
		default:
			return err
		}
	}

	return nil
}

// Here I decided to attempt an idiomatic version of the Delete service with
// a database transaction. Since this is updating just one entry in a single table
// an explicit db transaction isn't really necessary but I thought I'd practice it
// none the less. If using sqlc you'd probably not even worry about implementing
// it this way, but I am here to learn so.

const DeleteMovieQuery = `
	DELETE FROM movies WHERE id = $1`

func (m MovieModel) Delete(ctx context.Context, id int64) (err error) {

	if id < 1 {
		return ErrRecordNotFound
	}

	tx, err := m.db.BeginTx(ctx, pgx.TxOptions{})
	if err != nil {
		return err
	}
	defer func() {
		// If it's in error or the context was canceled, rollback
		if err != nil || ctx.Err() != nil {
			_ = tx.Rollback(ctx)
			return
		}
		// if the commit fails raises the error.
		err = tx.Commit(ctx)
	}()

	var cmd pgconn.CommandTag
	cmd, err = tx.Exec(ctx, DeleteMovieQuery, id)
	if err != nil {
		return err
	}

	if cmd.RowsAffected() == 0 {
		return ErrRecordNotFound
	}

	return nil
}

const GetAllMoviesQueryTemplate = `
    SELECT count(*) OVER(), id, created_at, title, year, runtime, genres, version
    FROM movies
    WHERE (to_tsvector('simple', title) @@ plainto_tsquery('simple', $1) OR $1 = '')
    AND (genres @> $2 OR $2 = '{}')
    ORDER BY %s %s, id ASC
	LIMIT $3 OFFSET $4`

func (m MovieModel) GetAll(ctx context.Context, title string, genres []string, filters Filters) ([]*Movie, Metadata, error) {
	// OLD query
	// query := `
	// 	SELECT id, created_at, title, year, runtime, genres, version
	// 	FROM movies
	// 	ORDER BY id ASC
	// 	`

	// The plainto_tsquery('simple', $1) function takes a search value and turns it
	// into a formatted query term that PostgreSQL full-text search can understand.
	// It normalizes the search value (again using the simple configuration), strips
	// any special characters, and inserts the and operator & between the words.
	// As an example, the search value "The Club" would result in the query term
	// 'the' & 'club'.

	// The @@ operator is the matches operator. In our statement we are using it to
	// check whether the generated query term matches the lexemes. To continue the
	// example, the query term 'the' & 'club' will match rows which contain both lexemes
	// 'the' and 'club'.

	// query := `
	//     SELECT id, created_at, title, year, runtime, genres, version
	//     FROM movies
	//      WHERE (to_tsvector('simple', title) @@ plainto_tsquery('simple', $1) OR $1 = '')
	//     AND (genres @> $2 OR $2 = '{}')
	//     ORDER BY id`

	// Using a window function to produce a totalRecords count using the WHERE parameters of
	// the query
	query := fmt.Sprintf(GetAllMoviesQueryTemplate, filters.sortColumn(), filters.sortDirection())

	// ctx want some timeout for queries. When used in the handler the context passed should
	// be the r.Context. Since cancel functions are inherited it will cancel on client
	// disconnect or on time out.
	ctxTimeout, cancel := context.WithTimeout(ctx, 3*time.Second)
	defer cancel()

	m.logger.Debug(query)

	args := []any{title, genres, filters.limit(), filters.offset()}

	rows, err := m.db.Query(ctxTimeout, query, args...)
	if err != nil {
		return nil, Metadata{}, err
	}
	defer rows.Close()

	totalRecords := 0
	movies := []*Movie{}

	for rows.Next() {
		var movie Movie
		err := rows.Scan(
			&totalRecords,
			&movie.ID,
			&movie.CreatedAt,
			&movie.Title,
			&movie.Year,
			&movie.Runtime,
			&movie.Genres,
			&movie.Version,
		)
		if err != nil {
			return nil, Metadata{}, err
		}
		movies = append(movies, &movie)
	}
	err = rows.Err()
	if err != nil {
		return nil, Metadata{}, err
	}

	metadata := calculateMetadata(totalRecords, filters.Page, filters.PageSize)

	return movies, metadata, nil
}

func ValidateMovie(v *validator.Validator, m *Movie) {

	v.Check(m.Title != "", "title", "must be provided")
	v.Check(len(m.Title) <= 500, "title", "must not be more than 500 bytes long")
	v.Check(m.Year != 0, "year", "must be provided")
	v.Check(m.Year >= 1888, "year", "must be greater than 1888")
	v.Check(m.Year <= int32(time.Now().Year()), "year", "must not be in the future")
	v.Check(m.Runtime != 0, "runtime", "must be provided")
	v.Check(m.Runtime > 0, "runtime", "must be a positive integer")
	v.Check(m.Genres != nil, "genres", "must be provided")
	v.Check(len(m.Genres) >= 1, "genres", "must contain one genre")
	v.Check(len(m.Genres) <= 5, "genres", "must not contain more than 5 genres")
	v.Check(validator.Unique(m.Genres), "genres", "must not contain duplicate values")
}