// Package gitea implements the internal Gitea REST operations used by delivery.
package gitea

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
)

type FailureKind string

const (
	FailureInvalid      FailureKind = "invalid_request"
	FailureNotFound     FailureKind = "not_found"
	FailureUnauthorized FailureKind = "unauthorized"
	FailureConflict     FailureKind = "conflict"
	FailureMalformed    FailureKind = "malformed_response"
	FailureUnverifiable FailureKind = "unverifiable"
	FailureTransport    FailureKind = "transport"
	FailureRejected     FailureKind = "rejected"
	FailureUnknown      FailureKind = "unknown"
)

// Failure describes how a Gitea operation failed. StatusCode is zero when no
// HTTP response was received.
type Failure struct {
	Kind       FailureKind
	Operation  string
	StatusCode int
	Err        error
}

func (f *Failure) Error() string {
	if f.StatusCode != 0 {
		return fmt.Sprintf("gitea %s: %s (HTTP %d)", f.Operation, f.Kind, f.StatusCode)
	}
	if f.Err != nil {
		return fmt.Sprintf("gitea %s: %s: %v", f.Operation, f.Kind, f.Err)
	}
	return fmt.Sprintf("gitea %s: %s", f.Operation, f.Kind)
}

func (f *Failure) Unwrap() error { return f.Err }

type Destination struct {
	BaseURL    string
	Owner      string
	Repository string
	Token      string
}

type release struct {
	ID         int64
	URL        string
	TagName    string
	Title      string
	Body       string
	Draft      bool
	Prerelease bool
}

type Client struct {
	HTTPClient *http.Client
}

type tagResponse struct {
	Commit struct {
		SHA string `json:"sha"`
	} `json:"commit"`
}

type releaseResponse struct {
	ID              int64  `json:"id"`
	HTMLURL         string `json:"html_url"`
	TagName         string `json:"tag_name"`
	TargetCommitish string `json:"target_commitish"`
	Name            string `json:"name"`
	Body            string `json:"body"`
	Draft           bool   `json:"draft"`
	Prerelease      bool   `json:"prerelease"`
}

type createReleaseRequest struct {
	TagName         string `json:"tag_name"`
	TargetCommitish string `json:"target_commitish"`
	Name            string `json:"name"`
	Body            string `json:"body"`
	Draft           bool   `json:"draft"`
	Prerelease      bool   `json:"prerelease"`
}

func (c Client) getRelease(ctx context.Context, client *http.Client, token, endpoint string) (release, int, error) {
	request, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
	if err != nil {
		return release{}, 0, failure(FailureInvalid, "find release", 0, err)
	}
	request.Header.Set("Authorization", "token "+token)
	request.Header.Set("Accept", "application/json")
	response, err := client.Do(request)
	if err != nil {
		return release{}, 0, failure(FailureTransport, "find release", 0, err)
	}
	defer response.Body.Close()
	if response.StatusCode == http.StatusNotFound {
		return release{}, response.StatusCode, failure(FailureNotFound, "find release", response.StatusCode, nil)
	}
	if response.StatusCode < 200 || response.StatusCode >= 300 {
		return release{}, response.StatusCode, responseFailure("find release", response.StatusCode)
	}
	var decoded releaseResponse
	if err := decodeJSON(response.Body, &decoded); err != nil {
		return release{}, response.StatusCode, failure(FailureMalformed, "decode release", response.StatusCode, err)
	}
	return decoded.release(), response.StatusCode, nil
}

func (c Client) getJSON(ctx context.Context, client *http.Client, token, operation, endpoint string, destination any) error {
	request, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
	if err != nil {
		return failure(FailureInvalid, operation, 0, err)
	}
	request.Header.Set("Authorization", "token "+token)
	request.Header.Set("Accept", "application/json")
	response, err := client.Do(request)
	if err != nil {
		return failure(FailureTransport, operation, 0, err)
	}
	defer response.Body.Close()
	if response.StatusCode < 200 || response.StatusCode >= 300 {
		return responseFailure(operation, response.StatusCode)
	}
	if err := decodeJSON(response.Body, destination); err != nil {
		return failure(FailureMalformed, operation, response.StatusCode, err)
	}
	return nil
}

func (c Client) postRelease(ctx context.Context, client *http.Client, token, endpoint string, body []byte) (release, int, error) {
	request, err := http.NewRequestWithContext(ctx, http.MethodPost, endpoint, bytes.NewReader(body))
	if err != nil {
		return release{}, 0, failure(FailureInvalid, "create release", 0, err)
	}
	request.Header.Set("Authorization", "token "+token)
	request.Header.Set("Accept", "application/json")
	request.Header.Set("Content-Type", "application/json")
	response, err := client.Do(request)
	if err != nil {
		return release{}, 0, failure(FailureTransport, "create release", 0, err)
	}
	defer response.Body.Close()
	if response.StatusCode < 200 || response.StatusCode >= 300 {
		return release{}, response.StatusCode, responseFailure("create release", response.StatusCode)
	}
	var decoded releaseResponse
	if err := decodeJSON(response.Body, &decoded); err != nil {
		return release{}, response.StatusCode, failure(FailureMalformed, "decode created release", response.StatusCode, err)
	}
	return decoded.release(), response.StatusCode, nil
}

func (c Client) httpClient() *http.Client {
	client := http.DefaultClient
	if c.HTTPClient != nil {
		clientCopy := *c.HTTPClient
		clientCopy.CheckRedirect = func(*http.Request, []*http.Request) error { return http.ErrUseLastResponse }
		return &clientCopy
	}
	clientCopy := *client
	clientCopy.CheckRedirect = func(*http.Request, []*http.Request) error { return http.ErrUseLastResponse }
	return &clientCopy
}

func parseBaseURL(raw string) (*url.URL, error) {
	parsed, err := url.Parse(raw)
	if err != nil {
		return nil, err
	}
	if (parsed.Scheme != "http" && parsed.Scheme != "https") || parsed.Host == "" || parsed.User != nil || parsed.RawQuery != "" || parsed.Fragment != "" {
		return nil, errors.New("base URL must be an absolute HTTP(S) origin or path without credentials, query, or fragment")
	}
	return parsed, nil
}

func (response releaseResponse) release() release {
	return release{ID: response.ID, URL: response.HTMLURL, TagName: response.TagName, Title: response.Name, Body: response.Body, Draft: response.Draft, Prerelease: response.Prerelease}
}

func validObjectID(value string) bool {
	if len(value) != 40 && len(value) != 64 {
		return false
	}
	for _, r := range value {
		if !(r >= '0' && r <= '9') && !(r >= 'a' && r <= 'f') {
			return false
		}
	}
	return true
}

func responseFailure(operation string, status int) error {
	kind := FailureRejected
	switch status {
	case http.StatusUnauthorized, http.StatusForbidden:
		kind = FailureUnauthorized
	case http.StatusConflict:
		kind = FailureConflict
	case http.StatusNotFound:
		kind = FailureNotFound
	}
	return failure(kind, operation, status, nil)
}

func failure(kind FailureKind, operation string, status int, err error) error {
	return &Failure{Kind: kind, Operation: operation, StatusCode: status, Err: err}
}

func decodeJSON(reader io.Reader, destination any) error {
	decoder := json.NewDecoder(reader)
	if err := decoder.Decode(destination); err != nil {
		return err
	}
	var trailing any
	if err := decoder.Decode(&trailing); !errors.Is(err, io.EOF) {
		if err == nil {
			return errors.New("response contains multiple JSON values")
		}
		return err
	}
	return nil
}