package backend

import (
	"bufio"
	"os"
	"strings"

	"ollie/paths"
)

// BackendConfig holds the per-backend configuration from backends.conf.
type BackendConfig struct {
	Key             string // API key / token
	URL             string // base URL override (empty = use backend's default)
	Model           string // default model override
	CompactionModel string // model used for history compaction (empty = use Model)
	Host            string // for ollama: host address
}

// configFile is the parsed contents of backends.conf: section name → key/value pairs.
type configFile struct {
	Default  string // top-level "backend = ..." selects the default
	Backends map[string]BackendConfig
}

// loadConfig reads ~/.config/ollie/backends.conf.
// Returns zero value if the file doesn't exist or is unreadable.
func loadConfig() configFile {
	return parseConfigFile(paths.CfgDir() + "/backends.conf")
}

// CompactionModel returns the configured compaction model for a backend.
// It falls back to that backend's configured default model when no dedicated
// compaction model is set.
func CompactionModel(name string) string {
	cfg := loadConfig()
	bc := cfg.Backends[name]
	if bc.CompactionModel != "" {
		return bc.CompactionModel
	}
	return bc.Model
}

// parseConfigFile parses an INI-style config file.
// Format:
//
//	backend = openrouter          (top-level: default backend selection)
//
//	[section]
//	key = value
//
// Lines starting with # are comments. Blank lines are ignored.
func parseConfigFile(path string) configFile {
	f, err := os.Open(path)
	if err != nil {
		return configFile{Backends: map[string]BackendConfig{}}
	}
	defer f.Close()

	cfg := configFile{Backends: map[string]BackendConfig{}}
	section := ""

	sc := bufio.NewScanner(f)
	for sc.Scan() {
		line := strings.TrimSpace(sc.Text())
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}
		// Section header.
		if strings.HasPrefix(line, "[") && strings.HasSuffix(line, "]") {
			section = strings.TrimSpace(line[1 : len(line)-1])
			if _, ok := cfg.Backends[section]; !ok {
				cfg.Backends[section] = BackendConfig{}
			}
			continue
		}
		// Key = value.
		k, v, ok := strings.Cut(line, "=")
		if !ok {
			continue
		}
		k = strings.TrimSpace(k)
		v = strings.TrimSpace(v)
		// Strip surrounding quotes.
		if len(v) >= 2 && (v[0] == '"' && v[len(v)-1] == '"' || v[0] == '\'' && v[len(v)-1] == '\'') {
			v = v[1 : len(v)-1]
		}

		// Top-level keys (before any section).
		if section == "" {
			if k == "backend" {
				cfg.Default = v
			}
			continue
		}

		bc := cfg.Backends[section]
		switch k {
		case "key":
			bc.Key = v
		case "url":
			bc.URL = v
		case "model":
			bc.Model = v
		case "compactionModel", "compaction_model", "compaction-model":
			bc.CompactionModel = v
		case "host":
			bc.Host = v
		}
		cfg.Backends[section] = bc
	}
	return cfg
}