// Package valueobjects holds the AI request and response values: Prompt,
// its messages and content parts, the ordered request Payload, and
// AIResponse.
package valueobjects

import (
	"bytes"
	"encoding/json"
	"maps"
	"slices"
)

// ContentPart is one block of a multimodal message: a text block, an
// image_url block (a data: URL or a remote URL, with detail) or a file
// block referencing an uploaded file id. The JSON shape is OpenAI's chat
// completions shape; the Anthropic adapter rewrites image and file blocks.
type ContentPart struct {
	Type     string    `json:"type"`
	Text     string    `json:"text,omitempty"`
	ImageURL *ImageURL `json:"image_url,omitempty"`
	File     *FileRef  `json:"file,omitempty"`
}

// ImageURL is an image_url block's target.
type ImageURL struct {
	URL    string `json:"url"`
	Detail string `json:"detail,omitempty"`
}

// FileRef is a file block's uploaded file id.
type FileRef struct {
	FileID string `json:"file_id"`
}

// Message is one conversation message. Its content is Text when Parts is
// nil, else the Parts list.
type Message struct {
	Role  string
	Text  string
	Parts []ContentPart
}

// Content is the message content as JSON encodes it: a string or the list
// of parts.
func (m Message) Content() any {
	if m.Parts != nil {
		return m.Parts
	}
	return m.Text
}

// MarshalJSON writes {"role":…,"content":…}.
func (m Message) MarshalJSON() ([]byte, error) {
	p := NewPayload()
	p.Set("role", m.Role)
	p.Set("content", m.Content())
	return p.MarshalJSON()
}

// Prompt is an immutable AI request: an optional system prompt, the
// messages, an optional model override and extra request options
// (temperature, max_tokens and the like, in insertion order). Every method
// returns a changed copy.
type Prompt struct {
	system   string
	messages []Message
	model    *string
	options  *Payload
}

// NewPrompt returns an empty prompt.
func NewPrompt() Prompt { return Prompt{} }

func (p Prompt) clone() Prompt {
	c := p
	c.messages = slices.Clone(p.messages)
	if p.options != nil {
		c.options = p.options.Clone()
	}
	return c
}

// WithSystem sets the system prompt.
func (p Prompt) WithSystem(system string) Prompt {
	c := p.clone()
	c.system = system
	return c
}

// AddUserMessage appends a user message.
func (p Prompt) AddUserMessage(content string) Prompt {
	return p.AddMessage("user", content)
}

// AddAssistantMessage appends an assistant message.
func (p Prompt) AddAssistantMessage(content string) Prompt {
	return p.AddMessage("assistant", content)
}

// AddMessage appends a message with role.
func (p Prompt) AddMessage(role, content string) Prompt {
	c := p.clone()
	c.messages = append(c.messages, Message{Role: role, Text: content})
	return c
}

// Image is one image of AddUserMessageWithImages: base64 data and its MIME
// type (image/jpeg when empty).
type Image struct {
	Base64   string
	MIMEType string
}

// AddUserMessageWithImage appends a user message carrying text and one
// base64 image as a data: URL with detail high. mimeType defaults to
// image/jpeg.
func (p Prompt) AddUserMessageWithImage(text, base64Image, mimeType string) Prompt {
	return p.AddUserMessageWithImages(text, []Image{{Base64: base64Image, MIMEType: mimeType}})
}

// AddUserMessageWithImages appends a user message carrying text and every
// image, in order.
func (p Prompt) AddUserMessageWithImages(text string, images []Image) Prompt {
	parts := []ContentPart{{Type: "text", Text: text}}
	for _, img := range images {
		mime := img.MIMEType
		if mime == "" {
			mime = "image/jpeg"
		}
		parts = append(parts, ContentPart{
			Type:     "image_url",
			ImageURL: &ImageURL{URL: "data:" + mime + ";base64," + img.Base64, Detail: "high"},
		})
	}
	c := p.clone()
	c.messages = append(c.messages, Message{Role: "user", Parts: parts})
	return c
}

// AddUserMessageWithFileID appends a user message carrying text and a
// reference to an uploaded file.
func (p Prompt) AddUserMessageWithFileID(text, fileID string) Prompt {
	c := p.clone()
	c.messages = append(c.messages, Message{Role: "user", Parts: []ContentPart{
		{Type: "text", Text: text},
		{Type: "file", File: &FileRef{FileID: fileID}},
	}})
	return c
}

// WithModel overrides the model id of the config the prompt is sent with.
func (p Prompt) WithModel(model string) Prompt {
	c := p.clone()
	c.model = &model
	return c
}

// WithOptions merges options into the prompt's options (PHP array_merge
// on string keys: a later value replaces an earlier one in place). keys
// fixes the order of new keys; keys missing from it follow sorted.
func (p Prompt) WithOptions(options map[string]any, keys ...string) Prompt {
	c := p.clone()
	if c.options == nil {
		c.options = NewPayload()
	}
	seen := map[string]bool{}
	for _, k := range keys {
		if v, ok := options[k]; ok && !seen[k] {
			c.options.Set(k, v)
			seen[k] = true
		}
	}
	for _, k := range slices.Sorted(maps.Keys(options)) {
		if !seen[k] {
			c.options.Set(k, options[k])
		}
	}
	return c
}

// SystemPrompt is the system prompt, "" when none.
func (p Prompt) SystemPrompt() string { return p.system }

// Messages is a copy of the messages.
func (p Prompt) Messages() []Message { return slices.Clone(p.messages) }

// Model is the model override, or nil.
func (p Prompt) Model() *string { return p.model }

// Options is a copy of the options in insertion order.
func (p Prompt) Options() *Payload {
	if p.options == nil {
		return NewPayload()
	}
	return p.options.Clone()
}

// ToAPIPayload is Prompt::toApiPayload, the OpenAI chat completions body:
// model (the override or defaultModel), messages with the system prompt
// first, then every option.
func (p Prompt) ToAPIPayload(defaultModel string) *Payload {
	messages := make([]Message, 0, len(p.messages)+1)
	if p.system != "" {
		messages = append(messages, Message{Role: "system", Text: p.system})
	}
	messages = append(messages, p.messages...)
	out := NewPayload()
	model := defaultModel
	if p.model != nil {
		model = *p.model
	}
	out.Set("model", model)
	out.Set("messages", messages)
	for _, k := range p.Options().Keys() {
		v, _ := p.options.Get(k)
		out.Set(k, v)
	}
	return out
}

// Payload is a JSON object that keeps its keys in insertion order, as a
// PHP array does. A Set on an existing key keeps its position.
type Payload struct {
	keys []string
	vals map[string]any
}

// NewPayload returns an empty payload.
func NewPayload() *Payload { return &Payload{vals: map[string]any{}} }

// Set stores v under k.
func (p *Payload) Set(k string, v any) {
	if _, ok := p.vals[k]; !ok {
		p.keys = append(p.keys, k)
	}
	p.vals[k] = v
}

// Get returns k's value.
func (p *Payload) Get(k string) (any, bool) {
	v, ok := p.vals[k]
	return v, ok
}

// Has reports whether k is set (PHP array_key_exists).
func (p *Payload) Has(k string) bool {
	_, ok := p.vals[k]
	return ok
}

// IsSet is PHP isset: k is present and not nil.
func (p *Payload) IsSet(k string) bool {
	v, ok := p.vals[k]
	return ok && v != nil
}

// Delete removes k.
func (p *Payload) Delete(k string) {
	if _, ok := p.vals[k]; !ok {
		return
	}
	delete(p.vals, k)
	p.keys = slices.DeleteFunc(p.keys, func(s string) bool { return s == k })
}

// Keys is the keys in order.
func (p *Payload) Keys() []string { return slices.Clone(p.keys) }

// Len is the number of keys.
func (p *Payload) Len() int { return len(p.keys) }

// Clone is a shallow copy.
func (p *Payload) Clone() *Payload {
	return &Payload{keys: slices.Clone(p.keys), vals: maps.Clone(p.vals)}
}

// Map is a copy of the values as a plain map.
func (p *Payload) Map() map[string]any { return maps.Clone(p.vals) }

// MarshalJSON writes the object in key order.
func (p *Payload) MarshalJSON() ([]byte, error) {
	var buf bytes.Buffer
	buf.WriteByte('{')
	for i, k := range p.keys {
		if i > 0 {
			buf.WriteByte(',')
		}
		kb, err := json.Marshal(k)
		if err != nil {
			return nil, err
		}
		buf.Write(kb)
		buf.WriteByte(':')
		vb, err := json.Marshal(p.vals[k])
		if err != nil {
			return nil, err
		}
		buf.Write(vb)
	}
	buf.WriteByte('}')
	return buf.Bytes(), nil
}