package runtime

import (
	"context"
	"fmt"
	"os"
	"strings"

	"github.com/evanw/esbuild/pkg/api"
	"github.com/fastschema/qjs"

	"reichard.io/poiesis/internal/functions"
	_ "reichard.io/poiesis/internal/stdlib"
)

type Runtime struct {
	ctx  *qjs.Context
	opts qjs.Option
}

func New(ctx context.Context, opts ...RuntimeOption) (*Runtime, error) {
	// Create Runtime
	r := &Runtime{opts: qjs.Option{Context: ctx}}
	for _, opt := range opts {
		opt(r)
	}

	// Create QuickJS Context
	rt, err := qjs.New(r.opts)
	if err != nil {
		return nil, err
	}
	r.ctx = rt.Context()

	// Populate Globals
	if err := r.populateGlobals(); err != nil {
		return nil, err
	}

	return r, nil
}

func (r *Runtime) populateGlobals() error {
	for name, fn := range functions.GetRegisteredFunctions() {
		// Register Main Function
		if fn.IsAsync() {
			r.ctx.SetAsyncFunc(name, func(this *qjs.This) {
				qjsVal, err := callFunc(this, fn)
				if err != nil {
					_ = this.Promise().Reject(this.Context().NewError(err))
					return
				}
				_ = this.Promise().Resolve(qjsVal)
			})
		} else {
			r.ctx.SetFunc(name, func(this *qjs.This) (*qjs.Value, error) {
				return callFunc(this, fn)
			})
		}
	}

	return nil
}

func (r *Runtime) RunFile(filePath string) error {
	tsFileContent, err := os.ReadFile(filePath)
	if err != nil {
		return fmt.Errorf("error reading file: %w", err)
	}

	return r.RunCode(string(tsFileContent))
}

func (r *Runtime) RunCode(tsCode string) error {
	transformedCode, err := r.transformCode(tsCode)
	if err != nil {
		return err
	}

	result, err := r.ctx.Eval("code.ts", qjs.Code(string(transformedCode)))
	if result != nil {
		result.Free()
	}
	return err
}

func (r *Runtime) transformCode(tsCode string) ([]byte, error) {
	result := api.Transform(tsCode, api.TransformOptions{
		Loader: api.LoaderTS,
		Target: api.ES2022,
		// Format:      api.FormatIIFE,
		Sourcemap:   api.SourceMapNone,
		TreeShaking: api.TreeShakingFalse,
	})

	if len(result.Errors) > 0 {
		var allErrs []string
		for _, e := range result.Errors {
			allErrs = append(allErrs, e.Text)
		}
		return nil, fmt.Errorf("transpilation failed: %s", strings.Join(allErrs, ", "))
	}

	return result.Code, nil
}

func callFunc(this *qjs.This, fn functions.Function) (*qjs.Value, error) {
	qjsArgs := this.Args()
	fnArgs := fn.Arguments()

	var allArgs []any
	for i := range min(len(fnArgs), len(qjsArgs)) {
		rVal, err := qjs.JsArgToGo(qjsArgs[i], fnArgs[i])
		if err != nil {
			panic(err)
		}
		allArgs = append(allArgs, rVal.Interface())
	}

	result, err := fn.Call(this.Context(), allArgs)
	if err != nil {
		return nil, err
	}

	val, err := qjs.ToJsValue(this.Context(), result)
	if err != nil {
		return nil, err
	}

	return val, nil
}