// compiler.el — el self-hosting compiler pipeline
//
// Wires lexer -> parser -> codegen into a single compile() function.
// This is the bootstrap entry point: compiled once by the Rust el-compiler,
// then self-hosted from that point forward.
//
// Two backends:
//   - C    (default)   compile()    -> emits C source linked against el_runtime.c
//   - JS   (--target=js) compile_js() -> emits JS source linked against el_runtime.js
//
// Compile the C output with:
//   cc -o <prog> <prog>.c el_runtime.c
//
// Run the JS output with:
//   node <prog>.js   (after copying el_runtime.js next to it)

import "lexer.el"
import "parser.el"
import "codegen.el"
import "codegen-js.el"

// compile — full pipeline (C target): source string -> C source string
fn compile(source: String) -> String {
    let tokens: [Map<String, Any>] = lex(source)
    let stmts: [Map<String, Any>] = parse(tokens)
    // Token list is no longer needed after parsing — release it to free memory
    // before codegen allocates its own working data on large source files.
    el_release(tokens)
    codegen(stmts, source)
}

// compile_js — full pipeline (JS target): source string -> JS source string
fn compile_js(source: String) -> String {
    let tokens: [Map<String, Any>] = lex(source)
    let stmts: [Map<String, Any>] = parse(tokens)
    // Token list is no longer needed after parsing — release it to free memory.
    el_release(tokens)
    codegen_js(stmts, source)
}

// compile_dispatch — pick a backend based on the requested target.
//   tgt = "c"  | "js"
// (The parameter is named `tgt` because `target` is a reserved keyword
//  in El's lexer — it would be tokenised as `Target`, breaking the
//  parser's identifier resolution.)
fn compile_dispatch(tgt: String, source: String) -> String {
    if str_eq(tgt, "js") { return compile_js(source) }
    compile(source)
}

// Detect a `--target=<lang>` flag in argv and return the target.
// Returns "c" if none specified or unrecognized.
fn detect_target(argv: [String]) -> String {
    let n: Int = native_list_len(argv)
    let i = 0
    while i < n {
        let a: String = native_list_get(argv, i)
        if str_starts_with(a, "--target=") {
            let v: String = str_slice(a, 9, str_len(a))
            return v
        }
        let i = i + 1
    }
    return "c"
}

// Strip flags from argv, leaving only positional arguments.
fn strip_flags(argv: [String]) -> [String] {
    let out: [String] = native_list_empty()
    let n: Int = native_list_len(argv)
    let i = 0
    while i < n {
        let a: String = native_list_get(argv, i)
        if !str_starts_with(a, "--") {
            let out = native_list_append(out, a)
        }
        let i = i + 1
    }
    return out
}

// ── Import resolution ────────────────────────────────────────────────────────
//
// elc supports two forms of import:
//   import "path/to/file.el"       — quoted relative path
//   from module import { Name }    — bare module name resolves to module.el
//                                    in the entry source's directory
//
// Codegen treats Import statements as no-ops (declarations only), so to
// actually link bodies across files we textually concatenate every imported
// source ahead of the entry source before lex/parse. resolve_imports does a
// depth-first traversal with deduplication so any module that gets pulled in
// transitively is included exactly once.

fn dirname_of(path: String) -> String {
    let n: Int = str_len(path)
    let i: Int = n - 1
    while i >= 0 {
        let c: String = str_slice(path, i, i + 1)
        if str_eq(c, "/") {
            return str_slice(path, 0, i)
        }
        let i = i - 1
    }
    return "."
}

// Extract the resolved file path from a single trimmed source line. Returns
// "" if the line is not an import.
fn parse_import_line(trimmed: String, dir: String) -> String {
    if str_starts_with(trimmed, "import \"") {
        let after: String = str_slice(trimmed, 8, str_len(trimmed))
        let q: Int = str_index_of(after, "\"")
        if q > 0 {
            let mod: String = str_slice(after, 0, q)
            return dir + "/" + mod
        }
    }
    if str_starts_with(trimmed, "from ") {
        let after: String = str_slice(trimmed, 5, str_len(trimmed))
        // module name is the first whitespace-delimited token
        let sp: Int = str_index_of(after, " ")
        if sp > 0 {
            let mod_raw: String = str_slice(after, 0, sp)
            let mod: String = str_trim(mod_raw)
            if !str_eq(mod, "") {
                return dir + "/" + mod + ".el"
            }
        }
    }
    return ""
}

// Recursively resolve imports starting from src_path. Returns the combined
// source text with every imported module's body inlined ahead of the entry
// source, deduplicated by absolute path. Uses state_set to track which paths
// have already been pulled in for this run.
fn resolve_imports(src_path: String) -> String {
    let seen_key: String = "__elc_imp__:" + src_path
    let already: String = state_get(seen_key)
    if !str_eq(already, "") { return "" }
    state_set(seen_key, "1")

    let source: String = fs_read(src_path)
    let dir: String = dirname_of(src_path)
    let lines: [String] = str_split(source, "\n")
    let n: Int = native_list_len(lines)

    // First pass: pull in every import body ahead of this file's body.
    let prefix: String = ""
    let body: String = ""
    let i: Int = 0
    while i < n {
        let line: String = native_list_get(lines, i)
        let trimmed: String = str_trim(line)
        let imp_path: String = parse_import_line(trimmed, dir)
        if !str_eq(imp_path, "") {
            let prefix = prefix + resolve_imports(imp_path)
        } else {
            let body = body + line + "\n"
        }
        let i = i + 1
    }
    return prefix + body
}

// main — CLI entry point.
//
//   elc <source.el>                            # emit C to stdout
//   elc --target=js <source.el>                # emit JS to stdout
//   elc --target=c  <source.el> <out.c>        # write C to file
//   elc --target=js <source.el> <out.js>       # write JS to file
fn main() -> Void {
    let argv: [String] = args()
    // Use `tgt` not `target`: `target` is a reserved keyword in the lexer
    // (Section 1.5 of the language spec). detect_target itself is fine
    // because the function-name position has no token-class restriction.
    let tgt: String = detect_target(argv)
    let positional: [String] = strip_flags(argv)
    let argc: Int = native_list_len(positional)
    if argc < 1 {
        println("el-compiler: usage: elc [--target=c|js] <source.el> [<output>]")
        exit(1)
    }
    let src_path: String = native_list_get(positional, 0)
    let source: String = resolve_imports(src_path)
    let out: String = compile_dispatch(tgt, source)
    if argc >= 2 {
        let out_path: String = native_list_get(positional, 1)
        let ok: Bool = fs_write(out_path, out)
        if ok {
            exit(0)
        } else {
            println("el-compiler: failed to write output")
            exit(1)
        }
    }
    // No output path: codegen streamed to stdout already; out is "".
}