package gitea

import (
	"context"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"strings"
)

// GenerateFromTemplateArgs is the request body for POST /repos/{owner}/{repo}/generate.
type GenerateFromTemplateArgs struct {
	Owner         string `json:"owner"`
	Name          string `json:"name"`
	Description   string `json:"description,omitempty"`
	Private       bool   `json:"private"`
	DefaultBranch string `json:"default_branch,omitempty"`
	GitContent    bool   `json:"git_content"` // include all template files
}

// GenerateFromTemplate creates a new repository from a template via POST /repos/{tmplOwner}/{tmplName}/generate.
func (c *Client) GenerateFromTemplate(ctx context.Context, tmplOwner, tmplName string, args GenerateFromTemplateArgs) (*Repo, error) {
	p := fmt.Sprintf("/api/v1/repos/%s/%s/generate", tmplOwner, tmplName)
	payload, err := json.Marshal(args)
	if err != nil {
		return nil, err
	}
	body, status, err := c.PostJSON(ctx, p, payload)
	if err != nil {
		return nil, err
	}
	if err := MapStatus(status, body); err != nil {
		return nil, err
	}
	var r Repo
	if err := json.Unmarshal(body, &r); err != nil {
		return nil, err
	}
	return &r, nil
}

// SubstituteFile reads a file from the given branch, applies string replacements,
// and writes it back if any changes were made. Best-effort — returns a wrapped error
// that includes the file path.
func (c *Client) SubstituteFile(ctx context.Context, owner, repo, branch, path string, replacements map[string]string) error {
	fc, err := c.GetFileContents(ctx, owner, repo, path, branch)
	if err != nil {
		return fmt.Errorf("read %s: %w", path, err)
	}
	decoded, err := base64.StdEncoding.DecodeString(fc.Content)
	if err != nil {
		return fmt.Errorf("decode %s: %w", path, err)
	}
	content := string(decoded)
	for k, v := range replacements {
		content = strings.ReplaceAll(content, k, v)
	}
	if content == string(decoded) {
		return nil // no changes, skip write
	}
	encoded := base64.StdEncoding.EncodeToString([]byte(content))
	_, err = c.UpsertFile(ctx, owner, repo, path, UpsertFileArgs{
		Branch:  branch,
		Content: encoded,
		Message: "Apply template substitutions",
		Sha:     fc.Sha,
	})
	if err != nil {
		return fmt.Errorf("write %s: %w", path, err)
	}
	return nil
}