package actions

import (
	"context"
	"errors"
	"fmt"
	"net/url"
	"strings"
	"time"

	"gitea.com/gitea/gitea-mcp/pkg/params"
	"gitea.com/gitea/gitea-mcp/pkg/to"

	"github.com/modelcontextprotocol/go-sdk/mcp"
)

const (
	defaultWaitForPRChecksTimeoutSeconds      = 120
	defaultWaitForPRChecksPollIntervalSeconds = 5
)

// terminalRunStatuses lists Gitea Actions run statuses that never transition
// further, independent of whether a "conclusion" field is also present.
var terminalRunStatuses = map[string]bool{
	"completed": true,
	"success":   true,
	"failure":   true,
	"cancelled": true,
	"skipped":   true,
	"failed":    true,
	"error":     true,
}

func isRunTerminal(run map[string]any) bool {
	if conclusion, ok := run["conclusion"].(string); ok && conclusion != "" {
		return true
	}
	status, _ := run["status"].(string)
	return terminalRunStatuses[strings.ToLower(status)]
}

func allRunsTerminal(runs []map[string]any) bool {
	for _, run := range runs {
		if !isRunTerminal(run) {
			return false
		}
	}
	return true
}

// waitForRunsUntilTerminal polls fetch until every run it returns is terminal
// or timeout elapses, sleeping pollInterval (capped to the remaining time)
// between polls so callers can inject a short pollInterval in tests.
func waitForRunsUntilTerminal(ctx context.Context, timeout, pollInterval time.Duration, fetch func(ctx context.Context) ([]map[string]any, error)) ([]map[string]any, bool, error) {
	deadline := time.Now().Add(timeout)
	for {
		runs, err := fetch(ctx)
		if err != nil {
			return nil, false, err
		}
		if allRunsTerminal(runs) {
			return runs, false, nil
		}

		remaining := time.Until(deadline)
		if remaining <= 0 {
			return runs, true, nil
		}
		wait := min(pollInterval, remaining)

		select {
		case <-ctx.Done():
			return runs, false, ctx.Err()
		case <-time.After(wait):
		}
	}
}

func fetchPullRequestHeadSHA(ctx context.Context, owner, repo string, pullNumber int64) (string, error) {
	var result map[string]any
	err := doJSONWithFallback(ctx, "GET",
		[]string{
			fmt.Sprintf("repos/%s/%s/pulls/%d", url.PathEscape(owner), url.PathEscape(repo), pullNumber),
		},
		nil, nil, &result,
	)
	if err != nil {
		return "", err
	}
	head, ok := result["head"].(map[string]any)
	if !ok {
		return "", errors.New("pull request response missing head")
	}
	sha, ok := head["sha"].(string)
	if !ok || sha == "" {
		return "", errors.New("pull request response missing head.sha")
	}
	return sha, nil
}

func fetchActionRunsForSHA(ctx context.Context, owner, repo, sha string) ([]map[string]any, error) {
	query := url.Values{}
	query.Set("head_sha", sha)

	var result map[string]any
	err := doJSONWithFallback(ctx, "GET",
		[]string{
			fmt.Sprintf("repos/%s/%s/actions/runs", url.PathEscape(owner), url.PathEscape(repo)),
		},
		query, nil, &result,
	)
	if err != nil {
		return nil, err
	}

	items, _ := result["workflow_runs"].([]any)
	runs := make([]map[string]any, 0, len(items))
	for _, item := range items {
		if run, ok := item.(map[string]any); ok {
			runs = append(runs, run)
		}
	}
	return runs, nil
}

func waitForPRChecksFn(ctx context.Context, args map[string]any) (*mcp.CallToolResult, error) {
	owner, err := params.GetString(args, "owner")
	if err != nil {
		return to.ErrorResult(err)
	}
	repo, err := params.GetString(args, "repo")
	if err != nil {
		return to.ErrorResult(err)
	}
	pullNumber, err := params.GetIndex(args, "pull_number")
	if err != nil || pullNumber <= 0 {
		return to.ErrorResult(errors.New("pull_number is required"))
	}

	timeoutSeconds := params.GetOptionalInt(args, "timeout_seconds", defaultWaitForPRChecksTimeoutSeconds)
	if timeoutSeconds <= 0 {
		timeoutSeconds = defaultWaitForPRChecksTimeoutSeconds
	}
	pollIntervalSeconds := params.GetOptionalInt(args, "poll_interval_seconds", defaultWaitForPRChecksPollIntervalSeconds)
	if pollIntervalSeconds <= 0 {
		pollIntervalSeconds = defaultWaitForPRChecksPollIntervalSeconds
	}

	sha, err := fetchPullRequestHeadSHA(ctx, owner, repo, pullNumber)
	if err != nil {
		return to.ErrorResult(fmt.Errorf("get pull request err: %v", err))
	}

	runs, timedOut, err := waitForRunsUntilTerminal(ctx,
		time.Duration(timeoutSeconds)*time.Second,
		time.Duration(pollIntervalSeconds)*time.Second,
		func(ctx context.Context) ([]map[string]any, error) {
			return fetchActionRunsForSHA(ctx, owner, repo, sha)
		},
	)
	if err != nil {
		return to.ErrorResult(fmt.Errorf("wait for pr checks err: %v", err))
	}

	slimmedRuns := make([]map[string]any, 0, len(runs))
	for _, run := range runs {
		slimmedRuns = append(slimmedRuns, slimRun(run))
	}
	return to.TextResult(map[string]any{
		"head_sha":  sha,
		"timed_out": timedOut,
		"runs":      slimmedRuns,
	})
}