package blog

import (
	"bytes"
	_ "embed"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"text/template"
	"time"

	"github.com/skratchdot/open-golang/open"
)

var (
	mergedURLFmt    = "https://api.github.com/search/issues?q=repo:go-gitea/gitea+is:pr+is:merged+milestone:%s"
	changelogURLFmt = "https://api.github.com/search/issues?q=repo:go-gitea/gitea+is:pr+is:merged+Changelog+%s"

	//go:embed release.md
	tmplContent string
	tmpl        = template.Must(template.New("").Parse(tmplContent))
)

// Merged is the API response for getting count of merged PRs in a milestone
type Merged struct {
	TotalCount int `json:"total_count"`
}

// FormatRelease formats a release template and injects author, milestone, changelog, and merged PR counts
func FormatRelease(author, milestone, changelog string) ([]byte, error) {
	resp, err := http.Get(fmt.Sprintf(mergedURLFmt, milestone))
	if err != nil {
		return nil, err
	}
	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	var merged Merged
	if err := json.Unmarshal(body, &merged); err != nil {
		return nil, err
	}

	date := time.Now()
	m := map[string]interface{}{
		"Author":    author,
		"Milestone": milestone,
		"Changelog": changelog,
		"Merged":    merged.TotalCount,
		"DateLong":  date.Format("2006-01-02T15:04:05+07:00"),
		"DateShort": date.Format("2006-01-02"),
	}

	var buf bytes.Buffer
	if err := tmpl.Execute(&buf, m); err != nil {
		return nil, err
	}

	return buf.Bytes(), nil
}

// Release is the API response for a release
type Release struct {
	Name        string    `json:"name"`
	PublishedAt time.Time `json:"published_at"`
}

// LatestRelease gets the latest release, used as a default for the generator
func LatestRelease() (Release, error) {
	var rel Release
	resp, err := http.Get("https://api.github.com/repos/go-gitea/gitea/releases/latest")
	if err != nil {
		return rel, err
	}
	defer resp.Body.Close()
	return rel, json.NewDecoder(resp.Body).Decode(&rel)
}

// ChangelogPR is the API response when searching for the milestone changelog PR
type ChangelogPR struct {
	Items []struct {
		HTMLURL string `json:"html_url"`
	} `json:"items"`
}

// OpenChangelogPullRequest attempts to open a browser to the changelog PR of a given milestone
func OpenChangelogPullRequest(milestone string) error {
	resp, err := http.Get(fmt.Sprintf(changelogURLFmt, milestone))
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	var pr ChangelogPR
	if err := json.NewDecoder(resp.Body).Decode(&pr); err != nil {
		return err
	}

	if len(pr.Items) == 0 {
		return errors.New("could not find changelog PR")
	}

	return open.Start(pr.Items[0].HTMLURL + "/files")
}