// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

package json

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"os"
	"sync"
	"time"

	"github.com/philippta/flyscrape"
)

func init() {
	flyscrape.RegisterModule(Module{})
}

type Module struct {
	Output struct {
		Format string `json:"format"`
		File   string `json:"file"`
	} `json:"output"`

	once bool
	w    io.WriteCloser
	mu   *sync.Mutex
}

func (Module) ModuleInfo() flyscrape.ModuleInfo {
	return flyscrape.ModuleInfo{
		ID:  "output.json",
		New: func() flyscrape.Module { return new(Module) },
	}
}

func (m *Module) Provision(ctx flyscrape.Context) {
	if m.disabled() {
		return
	}

	m.mu = &sync.Mutex{}

	if m.Output.File == "" {
		m.w = nopCloser{os.Stdout}
		return
	}

	f, err := os.Create(m.Output.File)
	if err != nil {
		log.Printf("failed to create file %q: %v", m.Output.File, err)
		os.Exit(1)
	}
	m.w = f
}

func (m *Module) ReceiveResponse(resp *flyscrape.Response) {
	if m.disabled() {
		return
	}

	if resp.Error == nil && resp.Data == nil {
		return
	}

	o := output{
		URL:       resp.Request.URL,
		Data:      resp.Data,
		Timestamp: time.Now(),
	}
	if resp.Error != nil {
		o.Error = resp.Error.Error()
	}

	m.mu.Lock()
	defer m.mu.Unlock()

	if !m.once {
		fmt.Fprintln(m.w, "[")
		m.once = true
	} else {
		fmt.Fprintln(m.w, ",")
	}

	var buf bytes.Buffer
	enc := json.NewEncoder(&buf)
	enc.SetEscapeHTML(false)
	enc.SetIndent("  ", "  ")
	enc.Encode(o)

	fmt.Fprint(m.w, "  ")
	fmt.Fprint(m.w, buf.String()[:buf.Len()-1])
}

func (m *Module) Finalize() {
	if m.disabled() {
		return
	}
	if m.once {
		fmt.Fprintln(m.w, "\n]")
	}
	m.w.Close()
}

func (m *Module) disabled() bool {
	return m.Output.Format != "json" && m.Output.Format != ""
}

type output struct {
	URL       string    `json:"url,omitempty"`
	Data      any       `json:"data,omitempty"`
	Error     string    `json:"error,omitempty"`
	Timestamp time.Time `json:"timestamp,omitempty"`
}

type nopCloser struct {
	io.Writer
}

func (c nopCloser) Write(p []byte) (n int, err error) {
	return c.Writer.Write(p)
}

func (c nopCloser) Close() error {
	return nil
}

var (
	_ flyscrape.Provisioner      = (*Module)(nil)
	_ flyscrape.ResponseReceiver = (*Module)(nil)
	_ flyscrape.Finalizer        = (*Module)(nil)
)