package main

import (
	"encoding"
	"encoding/json"
	"fmt"
	"net/url"
	"regexp"
	"strings"
	"time"
)

// httpGetGerritJSON is like [httpGetJSON], but
// https://gerrit-review.googlesource.com/Documentation/rest-api.html#output
func httpGetGerritJSON(u string, hdr map[string]string, out any) error {
	str, err := httpGet(u, hdr)
	if err != nil {
		return err
	}
	if _, body, ok := strings.Cut(str, "\n"); ok {
		str = body
	}
	return json.Unmarshal([]byte(str), out)
}

const GerritTimeFormat = "2006-01-02 15:04:05.000000000"

type GerritTime struct {
	Val time.Time
}

var (
	_ fmt.Stringer             = GerritTime{}
	_ encoding.TextMarshaler   = GerritTime{}
	_ encoding.TextUnmarshaler = (*GerritTime)(nil)
)

// String implements [fmt.Stringer].
func (t GerritTime) String() string {
	return t.Val.Format(GerritTimeFormat)
}

// MarshalText implements [encoding.TextMarshaler].
func (t GerritTime) MarshalText() ([]byte, error) {
	return []byte(t.String()), nil
}

// UnmarshalText implements [encoding.TextUnmarshaler].
func (t *GerritTime) UnmarshalText(data []byte) error {
	val, err := time.Parse(GerritTimeFormat, string(data))
	if err != nil {
		return err
	}
	t.Val = val
	return nil
}

type Gerrit struct{}

var _ Forge = Gerrit{}

var reGoogleGerritCL = regexp.MustCompile(`https://([a-z]+-review\.googlesource\.com)/c/([^?#]+)/\+/([0-9]+)(?:\?[^#]*)?(?:#.*)?$`)

func (Gerrit) FetchStatus(urls []string) (string, error) {
	for _, u := range urls {
		if reGitHubPR.MatchString(u) {
			return "", nil
		}
	}
	for _, u := range urls {
		m := reGoogleGerritCL.FindStringSubmatch(u)
		if m == nil {
			continue
		}
		authority := m[1]
		projectID := m[2]
		changeID := m[3]

		urlStr := "https://" + authority + "/changes/" + url.PathEscape(projectID) + "~" + changeID + "?o=MESSAGES&o=DETAILED_ACCOUNTS"

		var obj struct {
			Status string `json:"status"`
		}
		if err := httpGetGerritJSON(urlStr, nil, &obj); err != nil {
			return "", err
		}
		// https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#change-info
		switch obj.Status {
		case "NEW":
			return "open", nil
		case "MERGED":
			return "merged", nil
		case "ABANDONED":
			return "closed", nil
		}
	}
	return "", nil
}

func (Gerrit) FetchSubmittedAt(urls []string) (time.Time, error) {
	for _, u := range urls {
		if reGitHubPR.MatchString(u) {
			return time.Time{}, nil
		}
	}
	for _, u := range urls {
		m := reGoogleGerritCL.FindStringSubmatch(u)
		if m == nil {
			continue
		}
		authority := m[1]
		projectID := m[2]
		changeID := m[3]

		urlStr := "https://" + authority + "/changes/" + url.PathEscape(projectID) + "~" + changeID + "?o=MESSAGES&o=DETAILED_ACCOUNTS"

		var obj struct {
			Created GerritTime `json:"created"`
		}
		if err := httpGetGerritJSON(urlStr, nil, &obj); err != nil {
			return time.Time{}, err
		}
		return obj.Created.Val, nil
	}
	return time.Time{}, nil
}

func (Gerrit) FetchLastUpdated(urls []string) (time.Time, User, error) {
	for _, u := range urls {
		m := reGoogleGerritCL.FindStringSubmatch(u)
		if m == nil {
			continue
		}
		authority := m[1]
		projectID := m[2]
		changeID := m[3]

		urlStr := "https://" + authority + "/changes/" + url.PathEscape(projectID) + "~" + changeID + "?o=MESSAGES&o=DETAILED_ACCOUNTS"

		var obj struct {
			Updated  GerritTime `json:"updated"`
			Messages []struct {
				Author struct {
					AccountID   int    `json:"_account_id"`
					Name        string `json:"name"`
					DisplayName string `json:"display_name"`
				} `json:"author"`
				Date GerritTime `json:"date"`
			} `json:"messages"`
		}
		if err := httpGetGerritJSON(urlStr, nil, &obj); err != nil {
			return time.Time{}, User{}, err
		}
		retUpdatedAt := obj.Updated.Val
		var retUser User
		for _, message := range obj.Messages {
			if withinOneSecond(message.Date.Val, retUpdatedAt) {
				if message.Author.DisplayName != "" {
					retUser.Name = message.Author.DisplayName
				} else {
					retUser.Name = message.Author.Name
				}
				retUser.URL = fmt.Sprintf("https://%s/dashboard/%d", authority, message.Author.AccountID)
				break
			}
		}
		return retUpdatedAt, retUser, nil
	}
	return time.Time{}, User{}, nil
}