package sqlite

import (
	"bytes"
	"embed"
	"fmt"
	"sort"
	"text/template"

	"git.warky.dev/wdevs/relspecgo/pkg/models"
	"git.warky.dev/wdevs/relspecgo/pkg/writers"
)

//go:embed templates/*.tmpl
var templateFS embed.FS

// TemplateExecutor manages and executes SQLite SQL templates
type TemplateExecutor struct {
	templates *template.Template
	options   *writers.WriterOptions
}

// NewTemplateExecutor creates a new template executor for SQLite
func NewTemplateExecutor(opts *writers.WriterOptions) (*TemplateExecutor, error) {
	// Create template with SQLite-specific functions
	funcMap := GetTemplateFuncs(opts)

	tmpl, err := template.New("").Funcs(funcMap).ParseFS(templateFS, "templates/*.tmpl")
	if err != nil {
		return nil, fmt.Errorf("failed to parse templates: %w", err)
	}

	return &TemplateExecutor{
		templates: tmpl,
		options:   opts,
	}, nil
}

// Template data structures

// TableTemplateData contains data for table template
type TableTemplateData struct {
	Schema     string
	Name       string
	Columns    []*models.Column
	PrimaryKey *models.Constraint
}

// IndexTemplateData contains data for index template
type IndexTemplateData struct {
	Schema  string
	Table   string
	Name    string
	Columns []string
}

// ConstraintTemplateData contains data for constraint templates
type ConstraintTemplateData struct {
	Schema         string
	Table          string
	Name           string
	Columns        []string
	Expression     string
	ForeignSchema  string
	ForeignTable   string
	ForeignColumns []string
	OnDelete       string
	OnUpdate       string
}

// Execute methods

// ExecutePragmaForeignKeys executes the pragma foreign keys template
func (te *TemplateExecutor) ExecutePragmaForeignKeys() (string, error) {
	var buf bytes.Buffer
	err := te.templates.ExecuteTemplate(&buf, "pragma_foreign_keys.tmpl", nil)
	if err != nil {
		return "", fmt.Errorf("failed to execute pragma_foreign_keys template: %w", err)
	}
	return buf.String(), nil
}

// ExecuteCreateTable executes the create table template
func (te *TemplateExecutor) ExecuteCreateTable(data TableTemplateData) (string, error) {
	var buf bytes.Buffer
	err := te.templates.ExecuteTemplate(&buf, "create_table.tmpl", data)
	if err != nil {
		return "", fmt.Errorf("failed to execute create_table template: %w", err)
	}
	return buf.String(), nil
}

// ExecuteCreateIndex executes the create index template
func (te *TemplateExecutor) ExecuteCreateIndex(data IndexTemplateData) (string, error) {
	var buf bytes.Buffer
	err := te.templates.ExecuteTemplate(&buf, "create_index.tmpl", data)
	if err != nil {
		return "", fmt.Errorf("failed to execute create_index template: %w", err)
	}
	return buf.String(), nil
}

// ExecuteCreateUniqueConstraint executes the create unique constraint template
func (te *TemplateExecutor) ExecuteCreateUniqueConstraint(data ConstraintTemplateData) (string, error) {
	var buf bytes.Buffer
	err := te.templates.ExecuteTemplate(&buf, "create_unique_constraint.tmpl", data)
	if err != nil {
		return "", fmt.Errorf("failed to execute create_unique_constraint template: %w", err)
	}
	return buf.String(), nil
}

// ExecuteCreateCheckConstraint executes the create check constraint template
func (te *TemplateExecutor) ExecuteCreateCheckConstraint(data ConstraintTemplateData) (string, error) {
	var buf bytes.Buffer
	err := te.templates.ExecuteTemplate(&buf, "create_check_constraint.tmpl", data)
	if err != nil {
		return "", fmt.Errorf("failed to execute create_check_constraint template: %w", err)
	}
	return buf.String(), nil
}

// ExecuteCreateForeignKey executes the create foreign key template
func (te *TemplateExecutor) ExecuteCreateForeignKey(data ConstraintTemplateData) (string, error) {
	var buf bytes.Buffer
	err := te.templates.ExecuteTemplate(&buf, "create_foreign_key.tmpl", data)
	if err != nil {
		return "", fmt.Errorf("failed to execute create_foreign_key template: %w", err)
	}
	return buf.String(), nil
}

// Helper functions to build template data from models

// BuildTableTemplateData builds TableTemplateData from a models.Table
func BuildTableTemplateData(schema string, table *models.Table) TableTemplateData {
	columns := sortColumns(table.Columns)

	// Find primary key constraint
	var pk *models.Constraint
	for _, constraint := range sortConstraints(table.Constraints) {
		if constraint.Type == models.PrimaryKeyConstraint {
			pk = constraint
			break
		}
	}

	// If no explicit primary key constraint, build one from columns with IsPrimaryKey=true
	if pk == nil {
		pkCols := []string{}
		for _, col := range columns {
			if col.IsPrimaryKey {
				pkCols = append(pkCols, col.Name)
			}
		}
		if len(pkCols) > 0 {
			pk = &models.Constraint{
				Name:    "pk_" + table.Name,
				Type:    models.PrimaryKeyConstraint,
				Columns: pkCols,
			}
		}
	}

	return TableTemplateData{
		Schema:     schema,
		Name:       table.Name,
		Columns:    columns,
		PrimaryKey: pk,
	}
}

// sortColumns returns columns sorted by Sequence then Name for deterministic output.
func sortColumns(columns map[string]*models.Column) []*models.Column {
	result := make([]*models.Column, 0, len(columns))
	for _, col := range columns {
		result = append(result, col)
	}
	sort.Slice(result, func(i, j int) bool {
		if result[i].Sequence > 0 && result[j].Sequence > 0 {
			return result[i].Sequence < result[j].Sequence
		}
		return result[i].Name < result[j].Name
	})
	return result
}

// sortConstraints returns constraints sorted by Sequence then Name for deterministic output.
func sortConstraints(constraints map[string]*models.Constraint) []*models.Constraint {
	result := make([]*models.Constraint, 0, len(constraints))
	for _, c := range constraints {
		result = append(result, c)
	}
	sort.Slice(result, func(i, j int) bool {
		if result[i].Sequence > 0 && result[j].Sequence > 0 {
			return result[i].Sequence < result[j].Sequence
		}
		return result[i].Name < result[j].Name
	})
	return result
}

// sortIndexes returns indexes sorted by Sequence then Name for deterministic output.
func sortIndexes(indexes map[string]*models.Index) []*models.Index {
	result := make([]*models.Index, 0, len(indexes))
	for _, idx := range indexes {
		result = append(result, idx)
	}
	sort.Slice(result, func(i, j int) bool {
		if result[i].Sequence > 0 && result[j].Sequence > 0 {
			return result[i].Sequence < result[j].Sequence
		}
		return result[i].Name < result[j].Name
	})
	return result
}