package gitea

import (
	"context"
	"net/url"
	"strconv"
)

// Pull request states.
const (
	PRStateOpen   = "open"
	PRStateClosed = "closed"
	PRStateAll    = "all"
)

// Merge styles (Gitea's closed set; empty means "merge").
const (
	MergeMerge       = "merge"
	MergeRebase      = "rebase"
	MergeRebaseMerge = "rebase-merge"
	MergeSquash      = "squash"
	MergeFastForward = "fast-forward"
)

// PRBranch is one end of a pull request.
type PRBranch struct {
	Ref  string `json:"ref"`
	SHA  string `json:"sha"`
	Repo *Repo  `json:"repo"`
}

// PullRequest is the PR projection (read shape).
type PullRequest struct {
	Number    int64     `json:"number"`
	Title     string    `json:"title"`
	Body      string    `json:"body"`
	State     string    `json:"state"` // open|closed
	User      *User     `json:"user"`
	Base      *PRBranch `json:"base"`
	Head      *PRBranch `json:"head"`
	Mergeable bool      `json:"mergeable"`
	Merged    bool      `json:"merged"`
	MergedAt  string    `json:"merged_at"`
	HTMLURL   string    `json:"html_url"`
	CreatedAt string    `json:"created_at"`
	UpdatedAt string    `json:"updated_at"`
}

// PRParams is the PR-create write shape. Head may be "branch" (same
// repo) or "owner:branch" (fork syntax); the server resolves both.
type PRParams struct {
	Title string `json:"title"`
	Body  string `json:"body"`
	Base  string `json:"base"`
	Head  string `json:"head"`
}

// MergeParams is the merge write shape. Do is one of the Merge*
// constants (empty means "merge"); Title and Message are optional merge
// commit fields.
type MergeParams struct {
	Do      string
	Title   string
	Message string
}

type mergeWrite struct {
	Do           string `json:"Do"`
	MergeTitle   string `json:"MergeTitleField,omitempty"`
	MergeMessage string `json:"MergeMessageField,omitempty"`
}

// CreatePullRequest opens a PR and returns it.
func (c *Client) CreatePullRequest(ctx context.Context, owner, repo string, p PRParams) (*PullRequest, error) {
	var out PullRequest
	path := "/repos/" + url.PathEscape(owner) + "/" + url.PathEscape(repo) + "/pulls"
	if err := c.do(ctx, "POST", path, nil, p, &out); err != nil {
		return nil, err
	}
	return &out, nil
}

// ListPullRequests lists PRs filtered by state (PRStateOpen is the
// server default; PRStateAll lifts it).
func (c *Client) ListPullRequests(ctx context.Context, owner, repo, state string) ([]PullRequest, error) {
	var out []PullRequest
	var query url.Values
	if state != "" {
		query = url.Values{"state": []string{state}}
	}
	path := "/repos/" + url.PathEscape(owner) + "/" + url.PathEscape(repo) + "/pulls"
	if err := c.do(ctx, "GET", path, query, nil, &out); err != nil {
		return nil, err
	}
	return out, nil
}

// GetPullRequest fetches one PR by number.
func (c *Client) GetPullRequest(ctx context.Context, owner, repo string, number int64) (*PullRequest, error) {
	var out PullRequest
	path := "/repos/" + url.PathEscape(owner) + "/" + url.PathEscape(repo) + "/pulls/" + strconv.FormatInt(number, 10)
	if err := c.do(ctx, "GET", path, nil, nil, &out); err != nil {
		return nil, err
	}
	return &out, nil
}

// MergePullRequest merges an open PR. Re-merging or merging a closed PR
// maps to ErrValidation (http 409).
func (c *Client) MergePullRequest(ctx context.Context, owner, repo string, number int64, p MergeParams) error {
	if p.Do == "" {
		p.Do = MergeMerge
	}
	path := "/repos/" + url.PathEscape(owner) + "/" + url.PathEscape(repo) + "/pulls/" + strconv.FormatInt(number, 10) + "/merge"
	return c.do(ctx, "POST", path, nil, mergeWrite{Do: p.Do, MergeTitle: p.Title, MergeMessage: p.Message}, nil)
}